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Effective Date: February 14, 2004
Mandatory Compliance Date: August 14, 2004
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Technical Standards Document
Number 121, Revision 2
Air Brake Systems
(Ce document est aussi disponible en français.)
Introduction
As defined by section
12 of the Motor Vehicle Safety Act, a Technical Standards Document
(TSD) is a document that reproduces an enactment of a foreign government
(e.g. a Federal Motor Vehicle Safety Standard issued by the U.S. National
Highway Traffic Safety Administration). According to the Act, the Motor
Vehicle Safety Regulations may alter or override some provisions
contained in a TSD or specify additional requirements; consequently, it
is advisable to read a TSD in conjunction with the Act and its counterpart
Regulation. As a guide, where modifications have been made, the corresponding
clause number is indicated in the margin of the TSD within parentheses.
TSDs are revised from time to time in order to incorporate amendments
made to the reference document, at which time a Notice of Revision
is published in the Canada Gazette Part I. All TSDs are assigned
a revision number, with "Revision 0" designating the original version.
Identification of Changes
In order to facilitate the incorporation of a TSD, certain non-technical
changes may be made to the foreign enactment. These may include the
deletion of words, phrases, figures, or sections that do not apply
under the Act or Regulations, the conversion of imperial to metric
units, the deletion of superseded dates, and minor changes of an editorial
nature. Additions are underlined, and provisions that do not
apply are stroked through. Where an entire section
has been deleted, it is replaced by: "[CONTENT DELETED]".
Changes are also made where there is a reporting requirement or reference
in the foreign enactment that does not apply in Canada. For example,
the name and address of the U.S. Department of Transportation are
replaced by those of the Department of Transport.
Effective Dates
The original version of a TSD comes into effect on the date that
the regulation in which it is first incorporated by reference is published
in the Canada Gazette Part II. Subsequent revisions of a TSD
come into effect on the date of publication of the Notice of Revision
in the Canada Gazette Part I. The Effective Date is that
of the publication of the final amendment or the notice of revision
in the Canada Gazette. Compliance with the requirements of
a newly issued TSD is not mandatory until six months following the
effective date, during which time it is permissible to continue to
comply with the requirements of the previous Regulation or TSD. Manufacturers
and importers must comply with the requirements of a newly issued
TSD as of the Mandatory Compliance Date.
Official Version of Technical Standards Documents
Technical Standards Documents may be consulted electronically in
both HTML and Portable Document Format (PDF) on the Department of
Transports Web site at www.tc.gc.ca/RoadSafety/mvstm_tsd/index_e.htm.
The PDF version is a replica of the TSD as published by the Department
and is to be used for the purposes of legal interpretation and application.
The HTML version is provided for information purposes only.
(Original signed by)
Director, Standards Research and Development
for the Minister of Transport,
Ottawa, Ontario
Technical Standards Document
Number 121, Revision 2
AIR BRAKE SYSTEMS
The text of this document is based on the U.S. Code of Federal Regulations, Title 49, Part 571, Federal Motor Vehicle Safety Standard No. 121, Air brake systems,
revised as of October 1, 2002, and the Final Rule published in the Federal Register on August 11, 2003 (Vol. 68, No. 154, p. 47485).
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S1. Scope
This Technical Standards Document (TSD) standard establishes performance and equipment requirements for braking systems on vehicles equipped with air brake
systems.
S2. Purpose
The purpose of this TSD standard is to
insure safe braking performance under normal and emergency conditions.
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(1)
| S3. Application
This TSD standard applies to trucks, buses, and trailers
equipped with air brake systems. (For additional applicability
requirements, please see Schedule
III and section 121 of Schedule IV to the Motor Vehicle Safety
Regulations.) However, this TSD it does
not apply to:
(a) Any trailer that has a width of more than 2.6 m (102.36
in.) with extendable equipment in the fully retracted position and
that is equipped with two short-track axles in a line across the
width of the trailer;
(b) Any vehicle equipped with an axle that has a gross axle weight
rating (GAWR) of 13 154 kg (29,000 lb.) or more;
(c) Any truck or bus that has a speed attainable in 3.2 km
(2 mi.) of not more than 53.1 km/h (33 mph);
(d) Any truck that has a speed attainable in 3.2 km (2
mi.) of not more than 72.3 km/h (45 mph), an unloaded vehicle
mass weight that is not less than 95 percent
of its gross vehicle weight rating (GVWR), and no capacity to carry
occupants other than the driver and operating crew;
(e) Any trailer that has a GVWR of more than 54 432 kg (120,000
lb.) and whose body conforms to that described in the definition of "heavy
hauler trailer" set forth in S4 subsection
2(1) of the Motor Vehicle Safety Regulations;
(f) Any trailer that has an unloaded vehicle mass weight
which is not less than 95 percent of its GVWR; and
(g) Any load divider dolly.
S4. Definitions
Agricultural commodity trailer means a trailer that is designed
to transport bulk agricultural commodities in off-road harvesting
sites and to a processing plant or storage location, as evidenced
by skeletal construction that accommodates harvest containers, a maximum
length of 8.54 m (28 ft.), and an arrangement of air control
lines and reservoirs that minimizes damage in field operations. (remorque
pour produits agricoles)
* Air brake system means
a system that uses air as a medium for transmitting pressure or force
from the driver control to the service brake, including an air-over-hydraulic
brake subsystem, but does not include a system that uses compressed
air or vacuum only to assist the driver in applying muscular force
to hydraulic or mechanical components. (système
de freinage à air comprimé)
Air-over-hydraulic brake subsystem means a subsystem of the
air brake system that uses compressed air to transmit a force from
the driver control to a hydraulic brake system to actuate the service
brakes. (sous-système de freins hydropneumatiques)
* Antilock brake system or
ABS means a portion of a service brake system that
automatically controls the degree of rotational wheel slip during
braking by:
(1) sensing the rate of angular rotation of the wheels;
(2) transmitting signals regarding the rate of wheel angular
rotation to one or more controlling devices which interpret those
signals and generate responsive controlling output signals; and
(3) transmitting those controlling signals to one or more
modulators which adjust brake actuating forces in response to those
signals.
(dispositif de frein anti-blocage ou ABS)
Auto transporter means a truck and a trailer designed for
use in combination to transport motor vehicles, in that the towing
vehicle is designed to carry cargo at a location other than the fifth
wheel and to load this cargo only by means of the towed vehicle. (porte-autos)
Common diaphragm means a single brake chamber diaphragm which
is a component of the parking, emergency, and service brake systems.
(membrane commune)
Container chassis trailer means a semi-trailer of skeleton
construction limited to a bottom frame, one or more axles, especially
built and fitted with locking devices for the transport of intermodal
shipping containers, so that when the chassis and container are assembled,
the units serve the same function as an over-the-road trailer. (remorque
porte-conteneurs)
Directly controlled wheel means a wheel for which the degree
of rotational wheel slip is sensed, either at that wheel or on the
axle shaft for that wheel, and corresponding signals are transmitted
to one or more modulators that adjust the brake actuating forces at
that wheel. Each modulator may also adjust the brake actuating forces
at other wheels that are on the same axle or in the same axle set
in response to the same signal or signals. (roue commandée
directement)
Effective projected luminous lens area means that area of
the projection on a plane perpendicular to the lamp axis of that portion
of the light-emitting surface that directs light to the photometric
test pattern, and does not include mounting hole bosses, reflex reflector
area, beads, or rims that may glow or produce small areas of increased
intensity as a result of uncontrolled light from small areas (0.50-degree
radius around the test point). (surface effective de projection
lumineuse du verre diffuseur)
Full-treadle brake application means a brake application
in which the treadle valve pressure in any of the valve’s output
circuits reaches 585.7 kPa (85 psi) within 0.2 seconds after
the application is initiated, or in which maximum treadle travel is
achieved within 0.2 seconds after the application is initiated. (serrage
à fond des freins)
* Heavy hauler trailer means
a trailer which has one or more of the following characteristics,
but which is not a container chassis trailer:
(1) Its brake lines are designed to adapt to separation
or extension of the vehicle frame; or
(2) Its body consists only of a platform whose primary
cargo-carrying surface is not more than 40 inches above the ground
in an unloaded condition, except that it may include sides that
are designed to be easily removable and a permanentfront end structure"
as that term is used in §393.106 of this title.
(remorque lourde)
Independently controlled wheel means a directly controlled
wheel for which the modulator does not adjust the brake actuating
forces at any other wheel on the same axle. (roue commandée
séparément)
Indirectly controlled wheel means a wheel at which the degree
of rotational wheel slip is not sensed, but at which the modulator
of an antilock braking system adjusts its brake actuating forces in
response to signals from one or more sensed wheel(s). (roue commandée
indirectement)
Initial brake temperature means the average temperature of
the service brakes on the hottest axle of the vehicle 0.32 km
(0.2 mi.) before any brake application in the case of road tests,
or 18 seconds before any brake application in the case of dynamometer
testing. (température initiale des freins)
Intermodal shipping container means a reusable, transportable
enclosure that is especially designed with integral locking devices
for securing the container to the trailer to facilitate the efficient
and bulk shipping and transfer of goods by, or between, various modes
of transport, such as highway, rail, sea, and air. (conteneur universel)
* Load divider dolly means
a trailer composed of a trailer chassis and one or more axles, with
no solid bed, body, or container attached, and which is designed exclusively
to support a portion of the load on a trailer or truck excluded from
all the requirements of this standard. (chariot de répartition
de charge)
Maximum drive-through speed means the highest possible constant
speed at which the vehicle can be driven through 61 m (200
ft.) of a 152.4-m (500-ft.) radius curve arc without leaving
the 3.66-m (12-ft.) lane. (vitesse maximale en virage)
Maximum treadle travel means the distance that the treadle
moves from its position when no force is applied to its position when
the treadle reaches a full stop. (course maximale du distributeur)
Peak friction coefficient or PFC means the ratio of
the maximum value of braking test wheel longitudinal force to the
simultaneous vertical force occurring prior to wheel lockup, as the
braking torque is progressively increased. (coefficient maximal
de friction ou PFC)
Pulpwood trailer means a trailer that is designed exclusively
for harvesting logs or pulpwood and constructed with a skeletal frame
with no means for attachment of a solid bed, body, or container, and
with an arrangement of air control lines and reservoirs designed to
minimize damage in off-road operations. (remorque pour bois à
pâte)
Straddle trailer means a trailer that is designed to transport
bulk agricultural commodities from the harvesting location, as evidenced
by a framework that is driven over the cargo and lifting arms that
suspend the cargo for transit. (chariot cavalier)
Tandem axle means a group or set of two or more axles placed
in a close arrangement, one behind the other, with the centerlines
of adjacent axles not more than 1.83 m (72 inches) apart. (essieu
tandem)
Wheel lockup means 100 percent wheel slip. (blocage des
roues)
S5. Requirements
Each vehicle shall meet the following requirements under the conditions
specified in S6.
S5.1 Required equipment — Trucks and
buses
Each truck and bus shall have the following equipment: |
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S5.1.1 Air compressor. An air compressor of sufficient
capacity to increase air pressure in the supply and service reservoirs
from 585.7 kPa (85 pounds per square inch [psi]) to 689
kPa (100 psi) when the engine is operating at the vehicle manufacturer’s
maximum recommended r.p.m. within a time, in seconds, determined by
the quotient:
Actual reservoir capacity × 25
Required reservoir capacity
S5.1.1.1 Air compressor cut-in pressure. The air compressor
governor cut-in pressure for each bus shall be 585.7 kPa (85
psi) or greater. The air compressor governor cut-in pressure for each
truck shall be 689 kPa (100 psi) or greater.
S5.1.2 Reservoirs. One or more service reservoir systems,
from which air is delivered to the brake chambers, and either an automatic
condensate drain valve for each service reservoir or a supply reservoir
between the service reservoir system and the source of air pressure.
S5.1.2.1 The combined volume of all service reservoirs and
supply reservoirs shall be at least 12 times the combined volume of
all service brake chambers. For each brake-chamber type having a full
stroke at least as great as the first number in Column 1 of Table
V, but no more than the second number in Column 1 of Table V, the volume of each brake chamber,
for the purposes of calculating the required combined service and
supply reservoir volume, shall be either that specified in Column
2 of Table V or the actual volume of the brake
chamber at maximum travel of the brake piston or pushrod, whichever
is lower. The volume of a brake chamber not listed in Table
V is the volume of the brake chamber at maximum travel of the
brake piston or pushrod. The reservoirs of the truck portion of an
auto transporter need not meet this requirement for reservoir volume.
S5.1.2.2 Each reservoir shall be capable of withstanding
an internal hydrostatic pressure of five times the compressor cut-out
pressure or 3 445 kPa (500 psi), whichever is greater, for
10 minutes.
S5.1.2.3 Each service reservoir system shall be protected
against loss of air pressure due to failure or leakage in the system
between the service reservoir and the source of air pressure by check
valves or equivalent devices whose proper functioning can be checked
without disconnecting any air line or fitting.
S5.1.2.4 Each reservoir shall have a condensate drain valve
that can be manually operated.
S5.1.3 Towing vehicle protection system. If the vehicle is
intended to tow another vehicle equipped with air brakes, a system
to protect the air pressure in the towing vehicle from the effects
of a loss of air pressure in the towed vehicle.
S5.1.4 Pressure gauge. A pressure gauge in each service brake
system, readily visible to a person seated in the normal driving position,
that indicates the service reservoir system air pressure. The accuracy
of the gauge shall be within plus or minus 7 percent of the compressor
cut-out pressure.
S5.1.5 Warning signal. A signal, other than a pressure gauge,
that gives a continuous warning to a person in the normal driving
position when the ignition is in the "on" ("run") position and the air
pressure in the service reservoir system is below 413.4 kPa
(60 psi). The signal shall be either visible within the driver’s
forward field of view, or both audible and visible.
S5.1.6 Antilock Brake System
S5.1.6.1
(a) Each single-unit vehicle manufactured on or after
March 1, 1998 shall be equipped with an antilock brake
system that directly controls the wheels of at least one front axle
and the wheels of at least one rear axle of the vehicle. Wheels
on other axles of the vehicle may be indirectly controlled by the
antilock brake system.
(b) Each truck tractor manufactured on or after March
1, 1997 shall be equipped with an antilock brake system
that directly controls the wheels of at least one front axle and
the wheels of at least one rear axle of the vehicle, with the wheels
of at least one axle being independently controlled. Wheels on other
axles of the vehicle may be indirectly controlled by the antilock
brake system. A truck tractor shall have no more than three wheels
controlled by one modulator.
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(3)
| S5.1.6.2 Antilock Malfunction Signal
(a) Each truck tractor manufactured on or after March
1, 1997 and each single-unit vehicle manufactured
on or after March 1, 1998 shall be equipped with an indicator
lamp, mounted in front of and in clear view of the driver, which
is activated whenever there is a malfunction that affects the generation
or transmission of response or control signals in the vehicle’s
antilock brake system. The indicator lamp shall remain activated
as long as such a malfunction exists, whenever the ignition ("start")
switch is in the "on" ("run") position, whether or not the engine
is running. Each message about the existence of such a malfunction
shall be stored in the antilock brake system after the ignition
switch is turned to theoff" position and automatically reactivated
when the ignition switch is again turned to the "on" ("run") position.
The indicator lamp shall also be activated as a check of lamp function
whenever the ignition is turned to the "on" ("run") position. The
indicator lamp shall be deactivated at the end of the check of lamp
function unless there is a malfunction or a message about a malfunction
that existed when the key switch was last turned to theoff" position.
(b) Each truck tractor manufactured on or after March 1, 2001,
and each single-unit vehicle manufactured on or after March 1, 2001,
that is equipped to tow another air-braked vehicle, shall be equipped
with an electrical circuit that is capable of transmitting a malfunction
signal from the antilock brake system(s) on one or more towed vehicle(s)
(e.g., trailer[s] and dolly[ies]) to the trailer ABS malfunction
lamp in the cab of the towing vehicle, and shall have the means
for connection of this electrical circuit to the towed vehicle.
Each such truck tractor and single-unit vehicle shall also be equipped
with an indicator lamp, separate from the lamp required in S5.1.6.2(a),
mounted in front of and in clear view of the driver, which is activated
whenever the malfunction signal circuit described above receives
a signal indicating an ABS malfunction on one or more towed vehicle(s).
The indicator lamp shall remain activated as long as an ABS malfunction
signal from one or more towed vehicle(s) is present, whenever the
ignition ("start") switch is in the "on" ("run") position, whether
or not the engine is running. The indicator lamp shall also be activated
as a check of lamp function whenever the ignition is turned to the
on" ("run") position. The indicator lamp shall be deactivated at
the end of the check of lamp function unless a trailer ABS malfunction
signal is present.
S5.1.6.3 Antilock power circuit for towed vehicles. Each
truck tractor manufactured on or after March 1, 1997,
and each single-unit vehicle manufactured on or after March
1, 1998, that is equipped to tow another air-braked vehicle
shall be equipped with one or more electrical circuits that provide
continuous power to the antilock system on the towed vehicle or vehicles
whenever the ignition ("start") switch is in the "on" ("run") position.
Such a circuit shall be adequate to enable the antilock system on
each towed vehicle to be fully operable.
S5.1.7 Service brake stop lamp switch. A switch that lights
the stop lamps when the service brake control is statically depressed
to a point that produces a pressure of 41.3 kPa (6 psi) or
less in the service brake chambers.
S5.1.8 Brake distribution and automatic adjustment. Each
vehicle shall be equipped with a service brake system acting on all
wheels.
(a) Brake adjuster. Wear of the service brakes shall be
compensated for by means of a system of automatic adjustment. When
inspected pursuant to S5.9, the adjustment of the service brakes
shall be within the limits recommended by the vehicle manufacturer.
(b) Brake indicator. For each brake equipped with an external
automatic adjustment mechanism and having an exposed pushrod, the
condition of service brake under-adjustment shall be displayed by
a brake adjustment indicator in a manner that is discernible when
viewed with 20/40 vision from a location adjacent to or underneath
the vehicle, when inspected pursuant to S5.9.
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S5.2 Required equipment — Trailers
Each trailer shall have the following equipment:
S5.2.1 Reservoirs. One or more reservoirs to which the air
is delivered from the towing vehicle.
S5.2.1.1 The total volume of each service reservoir shall
be at least eight times the combined volume of all service brake chambers
serviced by that reservoir. For each brake-chamber type having a full
stroke at least as great as the first number in Column 1 of Table
V, but no more than the second number in Column 1, the volume
of each brake chamber, for the purposes of calculating the required
total service reservoir volume, shall be either that number specified
in Column 2 of Table V or the actual volume
of the brake chamber at maximum travel of the brake piston or pushrod,
whichever is lower. The volume of a brake chamber not listed in Table
V is the volume of the brake chamber at maximum travel of the brake
piston or pushrod. The reservoirs on a heavy hauler trailer and the
trailer portion of an auto transporter need not meet this requirement
for reservoir volume.
S5.2.1.2 Each reservoir shall be capable of withstanding
an internal hydrostatic pressure of 3 445 kPa (500 psi) for
10 minutes.
S5.2.1.3 Each reservoir shall have a condensate drain valve
that can be manually operated.
S5.2.1.4 Each service reservoir shall be protected against
loss of air pressure due to failure or leakage in the system between
the service reservoir and its source of air pressure by check valves
or equivalent devices.
S5.2.2 Brake distribution and automatic adjustment. Each
vehicle shall be equipped with a service brake system acting on all
wheels.
(a) Brake Adjuster. Wear of the service brakes shall be
compensated for by means of a system of automatic adjustment. When
inspected pursuant to S5.9, the adjustment of the service brakes
shall be within the limits recommended by the vehicle manufacturer.
(b) Brake Indicator. For each brake equipped with an external
automatic adjustment mechanism and having an exposed pushrod, the
condition of service brake under-adjustment shall be displayed by
a brake adjustment indicator in a manner that is discernible when
viewed with 20/40 vision from a location adjacent to or underneath
the vehicle, when inspected pursuant to S5.9.
S5.2.3 Antilock Brake System
S5.2.3.1
(a) Each semi-trailer (including a trailer converter dolly) manufactured
on or after March 1, 1998 shall be equipped with an antilock
brake system that directly controls the wheels of at least one axle
of the vehicle. Wheels on other axles of the vehicle may be indirectly
controlled by the antilock brake system.
(b) Each full trailer manufactured on or after March 1,
1998, shall be equipped with an antilock brake system that
directly controls the wheels of at least one front axle of the vehicle
and at least one rear axle of the vehicle. Wheels on other axles
of the vehicle may be indirectly controlled by the antilock brake
system.
S5.2.3.2 Antilock malfunction signal. Each trailer (including
a trailer converter dolly) manufactured on or after March 1, 2001,
that is equipped with an antilock brake system shall be equipped with
an electrical circuit that is capable of signaling a malfunction in
the trailer’s antilock brake system, and shall have the means
for connection of this antilock brake system malfunction signal circuit
to the towing vehicle. The electrical circuit need not be separate
or dedicated exclusively to this malfunction signaling function. The
signal shall be present whenever there is a malfunction that affects
the generation or transmission of response or control signals in the
trailer’s antilock brake system. The signal shall remain present
as long as the malfunction exists, whenever power is supplied to the
antilock brake system. Each message about the existence of such a
malfunction shall be stored in the antilock brake system whenever
power is no longer supplied to the system, and the malfunction signal
shall be automatically reactivated whenever power is again supplied
to the trailer’s antilock brake system. In addition, each trailer
manufactured on or after March 1, 2001, that is designed to tow another
air-brake- equipped trailer shall be capable of transmitting a malfunction
signal from the antilock brake system(s) of additional trailers it
tows to the vehicle towing it. |
(4)
| S5.2.3.3 Antilock malfunction indicator
(a) In addition to the requirements of S5.2.3.2, each trailer
and trailer converter dolly manufactured on or after March
1, 1998, and before March 1, 2009, shall be equipped with
an external antilock malfunction indicator lamp that meets the requirements
of S5.2.3.3 (b) through (d).
(b)(1) The lamp shall be designed to conform to the performance
requirements of Society of Automotive Engineers (SAE) Recommended
Practice J592 JUN92 or J592e July 1972, Clearance, Side Marker,
and Identification Lamps, for combination, clearance, and side
marker lamps, which are marked with aPC" orP2" on the lens or housing,
in accordance with SAE J759 Jan 95, Lighting Identification Code.
SAE J592 June 92, SAE J592e July 1972, and SAE J759 January
1995 are incorporated by reference and thereby are made part of
this standard. The Director of the Federal Register
approved the material incorporated by reference in accordance with
5 U.S.C. 552(a) and 1 CFR part 51. Copies of the material may be
inspected at NHTSA’s Docket Section, 400 Seventh Street, SW.,
room 5109, Washington, DC, or at the Office of the Federal Register,
800 North Capitol Street, NW., Washington, DC.
(2) The color of the lamp shall be yellow.
(3) The lettersABS" shall be permanently molded, stamped, or otherwise
marked or labeled in letters not less than 10 mm (0.4 in.)
high on the lamp lens or its housing to identify the function of
the lamp. Alternatively, the lettersABS" may be painted on the trailer
body or dolly, or a plaque with the lettersABS" may be affixed to
the trailer body or converter dolly; the lettersABS" shall be not
less than 25 mm (1 in.) high. A portion of one of the letters
in the alternative identification shall be not more than 150
mm (5.9 in.) from the edge of the lamp lens.
(c) Location requirements
(1) Each trailer that is not a trailer converter dolly shall be
equipped with a lamp mounted on a permanent structure on the left
side of the trailer as viewed from the rear, no closer than 150
mm (5.9 in.), and no farther than 600 mm (23.6 in.) from
the red rear side marker lamp, when measured between the closest
edge of the effective projected luminous lens area of each lamp.
(2) Each trailer converter dolly shall be equipped with a lamp
mounted on a permanent structure of the dolly so that the lamp is
not less than 375 mm (14.8 in.) above the road surface when
measured from the center of the lamp with the dolly at curb weight.
When a person, standing 3 m (9.8 ft.) from the lamp, views
the lamp from a perspective perpendicular to the vehicle’s centerline,
no portion of the lamp shall be obscured by any structure on the
dolly.
(3) Each trailer that is not a trailer converter dolly and on
which the malfunction indicator lamp cannot be placed within the
location specified in S5.2.3.3(c)(1) shall be equipped with a lamp
mounted on a permanent structure on the left side of the trailer
as viewed from the rear, near the red rear side marker lamp or on
the front face of the left rear fender of a trailer equipped with
fenders.
(d) The lamp shall be illuminated whenever power is supplied to
the antilock brake system and there is a malfunction that affects
the generation or transmission of response or control signals in
the trailer’s antilock brake system. The lamp shall remain illuminated
as long as such a malfunction exists and power is supplied to the
antilock brake system. Each message about the existence of such
a malfunction shall be stored in the antilock brake system whenever
power is no longer supplied to the system. The lamp shall be automatically
reactivated when power is again supplied to the trailer’s antilock
brake system. The lamp shall also be activated as a check of lamp
function whenever power is first supplied to the antilock brake
system and the vehicle is stationary. The lamp shall be deactivated
at the end of the check of lamp function, unless there is a malfunction
or a message about a malfunction that existed when power was last
supplied to the antilock brake system.
S5.3 Service brakes — Road
tests
The service brake system on each truck tractor shall, under the
conditions of S6, meet the requirements of S5.3.1, S5.3.3, S5.3.4,
and S5.3.6, when tested without adjustments other than those specified
in this TSD standard. The service brake system
on each bus and truck (other than a truck tractor shall) manufactured
before July 1, 2005, and each bus and truck (other than a truck tractor)
manufactured in two or more stages shall, under the conditions of
S6, meet the requirements of S5.3.1, S5.3.3, and S5.3.4 when tested
without adjustments other than those specified in this TSD
standard. The service brake system on each bus and
truck (other than a truck tractor) manufactured on or after July 1,
2005, and each bus and truck (other than a truck tractor) manufactured
in two or more stages on or after July 1, 2006, shall, under the conditions
of S6, meet the requirements of S5.3.1, S5.3.3, S5.3.4, and S5.3.6,
when tested without adjustments other than those specified in this
TSD standard. The service brake system on
each trailer shall, under the conditions of S6, meet the requirements
of S5.3.3, S5.3.4, and S5.3.5 when tested without adjustments other
than those specified in this TSD standard.
However, a heavy hauler trailer and the truck and trailer portions
of an auto transporter need not met the requirements of S5.3.
S5.3.1 Stopping distance — Trucks and buses. When stopped
six times for each combination of vehicle type, weight, and speed
specified in S5.3.1.1, in the sequence specified in Table
I, each truck tractor manufactured on or after March 1,
1997 and each single-unit vehicle manufactured on
or after March 1, 1998 shall stop at least once in not more
than the distance specified in Table II, measured
from the point at which movement of the service brake control begins,
without any part of the vehicle leaving the roadway, and with wheel
lockup permitted only as follows:
(a) At vehicle speeds above 32.2 km/h (20 mph), any wheel
on a nonsteerable axle other than the two rearmost nonliftable,
nonsteerable axles may lock up for any duration. The wheels on the
two rearmost nonliftable, nonsteerable axles, may lock up according
to (b).
(b) At vehicle speeds above 32.2 km/h (20 mph), one wheel
on any axle or two wheels on any tandem may lock up for any duration.
(c) At vehicle speeds above 32.2 km/h (20 mph), any wheel
not permitted to lock in (a) or (b) may lock up repeatedly, with
each lockup occurring for a duration of one second or less.
(d) At vehicle speeds of 32.2 km/h (20 mph) or less, any
wheel may lock up for any duration.
S5.3.1.1 Stop the vehicle from 96.6 km/h (60 mph)
on a surface with a peak friction coefficient of 0.9 with the vehicle
loaded as follows:
(a) Loaded to its GVWR so that the load on each axle, measured
at the tire-ground interface, is most nearly proportional to the
axles’ respective GAWRs, without exceeding the GAWR of any axle.
(b) In the truck tractor only configuration plus up to 226.8
kg (500 lbs.) or, at the manufacturer’s option, at its unloaded
mass weight plus up to 226.8 kg (500 lbs.)
(including driver and instrumentation) and plus not more than an
additional 453.6 kg (1,000 lbs.) for a roll bar structure
on the vehicle, and
(c) At its unloaded vehicle mass weight (except
for truck tractors) plus up to 226.8 kg (500 lbs.) (including
driver and instrumentation) or, at the manufacturer’s option, at
its unloaded mass weight plus up to 226.8 kg
(500 lbs.) (including driver and instrumentation) plus not more
than an additional 453.6 kg (1,000 lbs.) for a roll bar structure
on the vehicle. If the speed attainable in 3.2 km (two miles)
is less than 96.6 km/h (60 mph), the vehicle shall stop from
a speed in Table II that is 6.44 to 12.88
km/h (four to eight mph) less than the speed attainable in 3.2
km (two miles).
|
|
Table I — Stopping
sequence
| Truck
tractors
| Single-unit
trucks and buses
|
Burnish
| 1
| 1
|
Stability and Control at GVWR
(PFC 0.5)
| 2
| N/A
|
Stability and Control at LLVW
(PFC 0.5)
| 3
| 5
|
Manual Adjustment of Brakes
| 4
| N/A
|
96.6 km/h (60 mph)
Service Brake Stops at GVWR (PFC 0.9)
| 5
| 2
|
96.6 km/h (60 mph)
Emergency Service Brake Stops at GVWR (PFC 0.9)
| N/A
| 3
|
Parking Brake Test at GVWR
| 6
| 4
|
Manual Adjustment of Brakes
| 7
| 6
|
96.6 km/h (60 mph)
Service Brake Stops at LLVW (PFC 0.9)
| 8
| 7
|
96.6 km/h (60 mph)
Emergency Service Brake Stops at LLVW (PFC 0.9)
| 9
| 8
|
Parking Brake Test at LLVW
| 10
| 9
|
Final Inspection
| 11
| 10
|
Table II — Stopping
distance in metres (ft.)
Vehicle speed in
km/h (mph)
|
Service brake |
Emergency brake |
PFC 0.9
|
PFC 0.9
|
PFC 0.9
|
PFC 0.9
|
PFC 0.9
|
PFC 0.9
|
(1) |
(2) |
(3)
|
(4) |
(5) |
(6) |
40.3
(25)
48.3
(30)
56.4
(35)
64.4
(40)
72.5
(45)
80.5
(50)
88.6
(55)
96.6
(60) |
9.8
(32)
14.9
(49)
21.3
(70)
29.3
(96)
38.1
(125)
48.2
(158)
59.5
(195)
72.0
(236)
85.4
(280) |
10.7
(35)
16.5
(54)
23.8
(78)
32.3
(106)
42.1
(138)
53.4
(175)
65.9
(216)
79.6
(261)
94.5
(310) |
11.6
(38)
18.0
(59)
25.6
(84)
34.8
(114)
45.4
(149)
57.6
(189)
71.0
(233)
85.7
( 281)
102.1
(335) |
12.2
(40)
18.9
(62)
27.1
(89)
36.9
(121)
48.2
(158)
61.0
(200)
75.3
(247)
91.2
(299)
108.2
(355) |
25.3
(83)
37.5
(123)
51.8
(170)
68.6
(225)
87.8
(288)
109.2
(358)
132.6
(435)
158.5
(520)
186.9
(613) |
25.9
(85)
39.9
(131)
56.7
(186)
76.2
(250)
99.1
(325)
124.7
(409)
153.7
(504)
185.4
(608)
219.5
(720) |
NOTE:
(1) Loaded and unloaded buses
(2) Loaded single-unit trucks
(3) Unloaded truck tractors and single-unit trucks
(4) Loaded truck tractors tested with an unbraked control trailer
(5) All vehicles except truck tractors
(6) Unloaded truck tractors
|
| S5.3.2 [Reserved] S5.3.3
Brake actuation time. Each service brake system shall meet the
requirements of S5.3.3.1(a) and (b)
S5.3.3.1
(a) With an initial service reservoir system air pressure of 689
kPa (100 psi), the air pressure in each brake chamber shall,
when measured from the first movement of the service brake control,
reach 413.4 kPa (60 psi) in not more than 0.45 second in
the case of trucks and buses, 0.50 second in the case of trailers,
other than trailer converter dollies, designed to tow another vehicle
equipped with air brakes, 0.55 second in the case of trailer converter
dollies, and 0.60 second in the case of trailers other than trailers
designed to tow another vehicle equipped with air brakes. A vehicle
designed to tow another vehicle equipped with air brakes shall meet
the above actuation time requirement with a 0.819-L (50-cu.
in.) test reservoir connected to the control line output coupling.
A trailer, including a trailer converter dolly, shall meet the above
actuation time requirement with its control line input coupling
connected to the test rig shown in Figure 1.
(b) For a vehicle that is designed to tow another vehicle equipped
with air brakes, the pressure in the 0.819-L (50-cu. in.)
test reservoir referred to in S5.3.3.1(a) shall, when measured from
the first movement of the service brake control, reach 413.4
kPa (60 psi) not later than the time the fastest brake chamber
on the vehicle reaches 413.4 kPa (60 psi) or, at the option
of the manufacturer, in not more than 0.35 second in the case of
trucks and buses, 0.55 second in the case of trailer converter dollies,
and 0.50 second in the case of trailers other than trailer converter
dollies.
S5.3.4 Brake release time. Each service brake system shall
meet the requirements of S5.3.4.1(a) and (b).
S5.3.4.1
(a) With an initial service brake chamber air pressure of 654.6
kPa (95 psi), the air pressure in each brake chamber shall,
when measured from the first movement of the service brake control,
fall to 34.5 kPa(5 psi) in not more than 0.55 second in the
case of trucks and buses, 1.00 second in the case of trailers, other
than trailer converter dollies, designed to tow another vehicle
equipped with air brakes, 1.10 seconds in the case of trailer converter
dollies, and 1.20 seconds in the case of trailers other than trailers
designed to tow another vehicle equipped with air brakes. A vehicle
designated to tow another vehicle equipped with air brakes shall
meet the above release time requirement with a 0.819-L (50-cu.
in.) test reservoir connected to the control line output coupling.
A trailer, including a trailer converter dolly, shall meet the above
release time requirement with its control line input coupling connected
to the test rig shown in Figure 1.
(b) For vehicles designed to tow another vehicle equipped with
air brakes, the pressure in the 0.819-L (50-cu. in.) test
reservoir referred to in S5.3.4.1(a) shall, when measured from the
first movement of the service brake control, fall to 34.5 kPa
(5 psi) in not more than 0.75 second in the case of trucks and buses,
1.10 seconds in the case of trailer converter dollies, and 1.00
second in the case of trailers other than trailer converter dollies.
S5.3.5 Control signal pressure differential — Converter
dollies and trailers designed to tow another vehicle equipped with
air brakes
(a) For a trailer designed to tow another vehicle equipped with
air brakes, the pressure differential between the control line input
coupling and a 0.819-L (50-cu. in.) test reservoir attached
to the control line output coupling shall not exceed the values
specified in S5.3.5(a)(1), (2), and (3) under the conditions specified
in S5.3.5(b)(1) through (4):
(1) 6.9 kPa (1 psi) at all input pressures equal to or
greater than 34.5 kPa (5 psi), but not greater than 137.8
kPa (20 psi); and
(2) 13.8 kPa (2 psi) at all input pressures equal to or
greater than 137.8 kPa (20 psi), but not greater than 275.9
kPa (40 psi); and
(3) not more than a 5 percent differential at any input pressure
equal to or greater than 275.9 kPa (40 psi).
(b) The requirements in S5.3.5(a) shall be met
(1) When the pressure at the input coupling is steady, increasing,
or decreasing;
(2) When air is applied to or released from the control line input
coupling using the trailer test rig shown in Figure
1;
(3) With a fixed orifice consisting of a 0.46-mm (0.0180-in.)
diameter hole (no. 77 drill bit) in a 0.81-mm (0.032-in.)
thick disc installed in the control line between the trailer test
rig coupling and the vehicle’s control line input coupling;
and
(4) When operating the trailer test rig in the same manner
and under the same conditions as it is operated during testing to
measure brake actuation and release times, as specified in S5.3.3
and S5.3.4, except for the installation of the orifice in the control
line to restrict the airflow rate.
S5.3.6 Stability and control during braking — Trucks
and buses. When stopped four consecutive times for each combination
of weight, speed, and road conditions specified in S5.3.6.1 and S5.3.6.2,
each truck tractor shall stop at least three times within the 3.66
m (12 ft.) lane, without any part of the vehicle leaving the roadway.
When stopped four consecutive times for each combination of weight,
speed, and road conditions specified in S5.3.6.1 and S5.3.6.2, each
bus and truck (other than a truck tractor) manufactured on or after
July 1, 2005, and each bus and truck (other than a truck tractor)
manufactured in two or more stages on or after July 1, 2006, shall
stop at least three times within the 3.66 m (12 ft.) lane,
without any part of the vehicle leaving the roadway.
S5.3.6.1 Using a full-treadle brake application for the duration
of the stop, stop the vehicle from 48.3 km/h (30 mph) or 75
percent of the maximum drive-through speed, whichever is less, on
a 152.4-m (500-ft.) radius curved roadway with a wet level
surface having a peak friction coefficient of 0.5 when measured on
a straight or curved section of the curved roadway using an American
Society for Testing and Materials (ASTM) E1136 standard reference
tire, in accordance with ASTM Method E1337-90, at a speed of 64.4
km/h (40 mph) with water delivery.
S5.3.6.2 Stop the vehicle with the vehicle:
(a) Loaded to its GVWR, for a truck tractor, and
(b) At its unloaded mass weight plus up
to 226.8 kg (500 lb.) (including driver and instrumentation),
or at the manufacturer’s option, at its unloaded mass weight
plus up to 226.8 kg (500 lb.) (including driver and instrumentation)
and plus not more than an additional 453.6 kg (1,000 lb.)
for a roll bar structure on the vehicle, for a truck, bus, or truck
tractor.
|
|
S5.4 Service brake system — Dynamometer
tests
When tested without prior road testing, under the conditions of S6.2, each brake assembly shall meet the requirements of S5.4.1, S5.4.2, and S5.4.3 when tested in sequence and
without adjustments other than those specified in the TSD standard. For the purposes of the requirements of S5.4.2 and S5.4.3, an average deceleration rate
is the change in velocity divided by the deceleration time measured from the onset of deceleration.
S5.4.1 Brake retardation force. The sum of the retardation forces exerted by the brakes on each vehicle designed to be towed by another vehicle equipped with air brakes shall
be such that the quotient sum of the brake retardation forces/sum of GAWR’s, relative to brake chamber air pressure, shall have values not less than those shown in Column 1 of
Table III. The retardation force shall be determined as follows:
|
Table III — Brake retardation
force
Column 1
Brake retardation force/GAWR
| Column 2
Brake chamber pressure, kPa (psi)
|
0.05
| 137.8 (20)
|
0.12
| 206.7 (30)
|
0.18
| 275.6 (40)
|
0.25
| 344.5 (50)
|
0.31
| 413.4 (60)
|
0.37
| 482.3 (70)
|
0.41
| 551.2 (80)
|
| S5.4.1.1 After burnishing the brake
pursuant to S6.2.6, retain the brake assembly on the inertia dynamometer.
With an initial brake temperature between 51.7°C and 93.3°C
(125°F and 200°F), conduct a stop from 80.5 km/h (50
mph), maintaining brake chamber air pressure at a constant 137.8
kPa (20 psi). Measure the average torque exerted by the brake from
the time the specified air pressure is reached until the brake stops
and divide by the static loaded tire radius specified by the tire manufacturer
to determine the retardation force. Repeat the procedure six times,
increasing the brake chamber air pressure by 68.9 kPa (10 psi)
each time. After each stop, rotate the brake drum or disc until the
temperature of the brake falls to between 51.7°C and 93.3°C
(125°F and 200°F).
S5.4.2 Brake power. When mounted on an inertia dynamometer,
each brake shall be capable of making 10 consecutive decelerations
at an average rate of 2.72 m/s² (9 f.p.s.p.s.)
from 80.5 km/h (50 mph) to 24.2 km/h (15 mph), at equal
intervals of 72 seconds, and shall be capable of decelerating to a
stop from 32.2 km/h (20 mph) at an average deceleration rate
of 4.27 m/s² (14 f.p.s.p.s.) 1 minute after
the 10th deceleration. The series of decelerations shall be conducted
as follows:
S5.4.2.1 With an initial brake temperature between 65.6°C
and 93.3°C (150°F and 200°F) for the first brake application,
and the drum or disc rotating at a speed equivalent to 80.5 km/h
(50 mph), apply the brake and decelerate at an average deceleration
rate of 2.72 m/s² (9 f.p.s.p.s.) to 24.2
km/h (15 mph). Upon reaching 24.2 km/h (15 mph), accelerate
to 80.5 km/h (50 mph) and apply the brake for a second time
72 seconds after the start of the first application. Repeat the cycle
until 10 decelerations have been made. The service line air pressure
shall not exceed 689 kPa (100 psi) during any deceleration.
S5.4.2.2 One minute after the end of the last deceleration
required by S5.4.2.1 and with the drum or disc rotating at a speed
of 32.2 km/h (20 mph), decelerate to a stop at an average
deceleration rate of 4.27 m/s² (14 f.p.s.p.s.).
S5.4.3 Brake recovery. Except as provided in S5.4.3(a) and
(b), starting two minutes after completing the tests required by S5.4.2,
a vehicle’s brake shall be capable of making 20 consecutive stops
from 48.3 m/h (30 mph) at an average deceleration rate of 3.66
m/s² (12 f.p.s.p.s.), at equal intervals of one
minute measured from the start of each brake application. The service
line air pressure needed to attain a rate of 3.66 m/s²
(12 f.p.s.p.s.) shall be not more than 585.7 kPa (85 psi),
and not less than 137.8 kPa (20 psi), for a brake not subject
to the control of an antilock brake system, or 82.7 kPa (12
psi) for a brake subject to the control of an antilock brake system.
(a) Notwithstanding S5.4.3, neither front axle brake of a truck
tractor is subject to the requirements set forth in S5.4.3.
(b) Notwithstanding S5.4.3, neither front axle brake of a bus
or a truck, other than a truck tractor, is subject to the requirement
set forth in S5.4.3 prohibiting the service line air pressure from
being less than 137.8 kPa (20 psi) for a brake not subject
to the control of an antilock brake system or 82.7 kPa (12
psi) for a brake subject to the control of an antilock brake system.
|
|
S5.5 Antilock brake system
S5.5.1 Antilock brake system malfunction. On a truck tractor manufactured on or after March 1, 1997, that is equipped with an antilock brake system and a
single-unit vehicle manufactured on or after March 1, 1998, that is equipped with an antilock brake system, a malfunction that affects the generation or
transmission of response or control signals of any part of the antilock brake system shall not increase the actuation and release times of the service brakes.
S5.5.2 Antilock system power Trailers. On a trailer (including a trailer converter dolly) manufactured on or after March 1, 1998 that is equipped with an
antilock system that requires electrical power for operation, the power shall be obtained from the towing vehicle through one or more electrical circuits which provide continuous
power whenever the powered vehicle’s ignition ("start") switch is in the "on" ("run") position. The antilock system shall automatically receive power from the stop lamp
circuit, if the primary circuit or circuits are not functioning. Each trailer (including a trailer converter dolly) manufactured on or after March 1, 1998 that is
equipped to tow another air-braked vehicle shall be equipped with one or more circuits which provide continuous power to the antilock system on the vehicle(s) it tows. Such circuits
shall be adequate to enable the antilock system on each towed vehicle to be fully operable.
|
| S5.6 Parking
brake system
(a) Except as provided in S5.6(b) and S5.6(c), each vehicle other
than a trailer converter dolly shall have a parking brake system
that under the conditions of S6.1 meets the requirements of:
(1) S5.6.1 or S5.6.2, at the manufacturer’s option, and
(2) S5.6.3, S5.6.4, S5.6.5, and S5.6.6.
(b) At the option of the manufacturer, for vehicles equipped with
brake systems which incorporate a common diaphragm, the performance
requirements specified in S5.6(a), which must be met with any single
leakage-type failure in a common diaphragm, may instead be met with
the level of leakage-type failure determined in S5.6.7. The election
of this option does not affect the performance requirements specified
in S5.6(a), which apply with single leakage-type failures other
than failures in a common diaphragm.
(c) At the option of the manufacturer, the trailer portion of
any agricultural commodity trailer, heavy hauler trailer, or pulpwood
trailer may meet the requirements of §393.43 of Title 49
of the Code of Federal Regulations (the most recent edition)
this title instead of the requirements of S5.6(a).
|
(5)
| S5.6.1 Static retardation force.
With all other brakes rendered inoperative, during a static drawbar
pull in a forward or rearward direction, the static retardation force
produced by the application of the parking brakes shall be:
(a) In the case of a vehicle other than a truck tractor that is
equipped with more than two axles, such that the quotient of static
retardation force/GAWR is not less than 0.28 for any axle other
than a steerable front axle; and
(b) In the case of a truck tractor that is equipped with more
than two axles, such that the quotient of static retardation force/GVWR
is not less than 0.14.
S5.6.2 Grade holding. With all parking brakes applied, the
vehicle shall remain stationary facing uphill and facing downhill
on a smooth, dry, portland cement concrete roadway with a 20-percent
grade, both:
(a) when loaded to its GVWR, and
(b) at its unloaded vehicle mass weight plus 680.4
kg (1500 lb.) (including driver and instrumentation and roll
bar).
S5.6.3 Application and holding. Each parking brake system
shall meet the requirements of S5.6.3.1 through S5.6.3.4.
S5.6.3.1 The parking brake system shall be capable of achieving
the minimum performance specified either in S5.6.1 or S5.6.2 with
any single leakage-type failure, in any other brake system, of a part
designed to contain compressed air or brake fluid (excluding failure
of a component of a brake chamber housing, but including failure of
any brake chamber diaphragm that is part of any other brake system,
including a diaphragm which is common to the parking brake system
and any other brake system), when the pressures in the vehicle’s
parking brake chambers are at the levels determined in S5.6.3.4.
S5.6.3.2 A mechanical means shall be provided that, after
a parking brake application is made with the pressures in the vehicle’s
parking brake chambers at the levels determined in S5.6.3.4, and all
air and fluid pressures in the vehicle’s braking systems are then
bled down to zero, and without using electrical power, holds the parking
brake application with sufficient parking retardation force to meet
the minimum performance specified in S5.6.3.1 and in either S5.6.1
or S5.6.2.
S5.6.3.3 For trucks and buses, with an initial reservoir
system pressure of 689 kPa (100 psi) and, if designed to tow
a vehicle equipped with air brakes, with a 0.819-L (50-cu.
in.) test reservoir connected to the supply line coupling, no later
than three seconds from the time of actuation of the parking brake
control, the mechanical means referred to in S5.6.3.2 shall be actuated.
For trailers, with the supply line initially pressurized to 689
kPa (100 psi) using the supply line portion of the trailer test
rig (Figure 1) and, if designed to tow a
vehicle equipped with air brakes, with a 0.819-L (50-cu. in.)
test reservoir connected to the rear supply line coupling, no later
than three seconds from the time venting to the atmosphere of the
front supply line coupling is initiated, the mechanical means referred
to in S5.6.3.2 shall be actuated. This requirement shall be met for
trucks, buses, and trailers both with and without any single leakage-type
failure, in any other brake system, of a part designed to contain
compressed air or brake fluid (consistent with the parenthetical phrase
specified in S5.6.3.1).
S5.6.3.4 The parking brake chamber pressures for S5.6.3.1
and S5.6.3.2 are determined as follows. For trucks and buses, with
an initial reservoir system pressure of 689 kPa (100 psi) and,
if designed to tow a vehicle equipped with air brakes, with a 0.819-L
(50-cu. in.) test reservoir connected to the supply line coupling,
any single leakage-type failure, in any other brake system, of a part
designed to contain compressed air or brake fluid (consistent with
the parenthetical phrase specified in S5.6.3.1), is introduced in
the brake system. The parking brake control is actuated and the pressures
in the vehicle’s parking brake chambers are measured three seconds
after that actuation is initiated. For trailers, with the supply line
initially pressurized to 689 kPa (100 psi) using the supply
line portion of the trailer test rig (Figure
1) and, if designed to tow a vehicle equipped with air brakes,
with a 0.819-L (50-cu. in.) test reservoir connected to the
rear supply line coupling, any single leakage-type failure, in any
other brake system, of a part designed to contain compressed air or
brake fluid (consistent with the parenthetical phrase specified in
S5.6.3.1), is introduced in the brake system. The front supply line
coupling is vented to the atmosphere and the pressures in the vehicle’s
parking brake chambers are measured three seconds after that venting
is initiated.
S5.6.4 Parking brake control — Trucks and buses. The
parking brake control shall be separate from the service brake control.
It shall be operable by a person seated in the normal driving position.
The control shall be identified in a manner that specifies the method
of control operation. The parking brake control shall control the
parking brakes of the vehicle and of any air-braked vehicle that it
is designed to tow.
S5.6.5 Release performance. Each parking brake system shall
meet the requirements specified in S5.6.5.1 through S5.6.5.4.
S5.6.5.1 For trucks and buses, with initial conditions as
specified in S5.6.5.2, at all times after an application actuation
of the parking brake control, and with any subsequent level of pressure,
or combination of levels of pressure, in the reservoirs of any of
the vehicle’s brake systems, no reduction in parking brake retardation
force shall result from a release actuation of the parking brake control
unless the parking brakes are capable, after such release, of being
reapplied at a level meeting the minimum performance specified either
in S5.6.1 or S5.6.2. This requirement shall be met both with and without
the engine on, and with and without single leakage-type failure, in
any other brake system, of a part designed to contain compressed air
or brake fluid (consistent with the parenthetical phrase specified
in S5.6.3.1).
S5.6.5.2 The initial conditions for S5.6.5.1 are as follows.
The reservoir system pressure is 689 kPa (100 psi). If the
vehicle is designed to tow a vehicle equipped with air brakes, a 0.819-L
(50-cu. in.) test reservoir is connected to the supply line coupling.
S5.6.5.3 For trailers, with initial conditions as specified
in S5.6.5.4, at all times after actuation of the parking brakes by
venting the front supply line coupling to the atmosphere, and with
any subsequent level of pressure, or combination of levels of pressure,
in the reservoirs of any of the vehicle’s brake systems, the parking
brakes shall not be releasable by repressurizing the supply line using
the supply line portion of the trailer test rig (Figure
1) to any pressure above 482.3 kPa (70 psi), unless the
parking brakes are capable, after such release, of reapplication by
subsequent venting of the front supply line coupling to the atmosphere,
at a level meeting the minimum performance specified either in S5.6.1
or S5.6.2. This requirement shall be met both with and without any
single leakage-type failure, in any other brake system, of a part
designed to contain compressed air or brake fluid (consistent with
the parenthetical phrase specified in S5.6.3.1).
S5.6.5.4 The initial conditions for S5.6.5.3 are as follows.
The reservoir system and supply line are pressurized to 689 kPa
(100 psi), using the supply line portion of the trailer test rig (Figure
1). If the vehicle is designed to tow a vehicle equipped with
air brakes, a 0.819-L (50-cu. in.) test reservoir is connected
to the rear supply line coupling.
S5.6.6 Accumulation of actuation energy. Each parking brake
system shall meet the requirements specified in S5.6.6.1 through S5.6.6.6.
S5.6.6.1 For trucks and buses, with initial conditions as
specified in S5.6.6.2, the parking brake system shall be capable of
meeting the minimum performance specified either in S5.6.1 or S5.6.2,
with any single leakage-type failure, in any other brake system, of
a part designed to contain compressed air or brake fluid (consistent
with the parenthetical phrase specified in S5.6.3.1), at the conclusion
of the test sequence specified in S5.6.6.3.
S5.6.6.2 The initial conditions for S5.6.6.1 are as follows.
The engine is on. The reservoir system pressure is 689 kPa
(100 psi). If the vehicle is designed to tow a vehicle equipped with
air brakes, a 0.819-L (50-cu. in.) test reservoir is connected
to the supply line coupling.
S5.6.6.3 The test sequence for S5.6.6.1 is as follows. The
engine is turned off. Any single leakage-type failure, in any other
brake system, of a part designed to contain compressed air or brake
fluid (consistent with the parenthetical phrase specified in S5.6.3.1),
is then introduced in the brake system. An application actuation of
the parking brake control is then made. Thirty seconds after such
actuation, a release actuation of the parking brake control is made.
Thirty seconds after the release actuation, a final application actuation
of the parking brake control is made.
S5.6.6.4 For trailers, with initial conditions as specified
in S5.6.6.5, the parking brake system shall be capable of meeting
the minimum performance specified either in S5.6.1 or S5.6.2, with
any single leakage-type failure, in any other brake system, of a part
designed to contain compressed air or brake fluid (consistent with
the parenthetical phrase specified in S5.6.3.1), at the conclusion
of the test sequence specified in S5.6.6.6.
S5.6.6.5 The initial conditions for S5.6.6.4 are as follows.
The reservoir system and supply line are pressurized to 689 kPa
(100 psi), using the supply line portion of the trailer test rig (Figure
1). If the vehicle is designed to tow a vehicle equipped with
air brakes, a 0.819-L (50-cu. in.) test reservoir is connected
to the rear supply line coupling.
S5.6.6.6 The test sequence for S5.6.6.4 is as follows. Any
single leakage-type failure, in any other brake system, of a part
designed to contain compressed air or brake fluid (consistent with
the parenthetical phrase specified in S5.6.3.1), is introduced in
the brake system. The front supply line coupling is vented to the
atmosphere. Thirty seconds after the initiation of such venting, the
supply line is repressurized with the trailer test rig (Figure
1). Thirty seconds after the initiation of such repressurizing
of the supply line, the front supply line is vented to the atmosphere.
This procedure is conducted either by connection and disconnection
of the supply line coupling or by use of a valve installed in the
supply line portion of the trailer test rig near the supply line coupling.
S5.6.7 Maximum level of common diaphragm leakage-type failure
(Equivalent level of leakage from the air chamber containing that
diaphragm). In the case of vehicles for which the option in S5.6(b)
has been elected, determine the maximum level of common diaphragm
leakage-type failure (or equivalent level of leakage from the air
chamber containing that diaphragm) according to the procedures set
forth in S5.6.7.1 through S5.6.7.2.3.
S5.6.7.1 Trucks and buses
S5.6.7.1.1 According to the following procedure, determine
the threshold level of common diaphragm leakage-type failure (or equivalent
level of leakage from the air chamber containing that diaphragm) at
which the vehicle’s parking brakes become unreleasable. With an
initial reservoir system pressure of 689 kPa (100 psi), the
engine turned off, no application of any of the vehicle’s brakes,
and, if the vehicle is designed to tow a vehicle equipped with air
brakes, a 0.819-L (50-cu. in.) test reservoir connected to
the supply line coupling, introduce a leakage-type failure of the
common diaphragm (or equivalent leakage from the air chamber containing
that diaphragm). Apply the parking brakes by making an application
actuation of the parking brake control. Reduce the pressures in all
of the vehicle’s reservoirs to zero, turn on the engine and allow
it to idle, and allow the pressures in the vehicle’s reservoirs
to rise until they stabilize or until the compressor shut-off point
is reached. At that time, make a release actuation of the parking
brake control, and determine whether all of the mechanical means referred
to in S5.6.3.2 continue to be actuated and hold the parking brake
applications with sufficient parking retardation force to meet the
minimum performance specified in either S5.6.1 or S5.6.2. Repeat this
procedure with progressively decreasing or increasing levels (whichever
is applicable) of leakage-type diaphragm failures or equivalent leakages,
to determine the minimum level of common diaphragm leakage-type failure
(or equivalent level of leakage from the air chamber containing that
diaphragm) at which all of the mechanical means referred to in S5.6.3.2
continue to be actuated and hold the parking brake applications with
sufficient parking retardation forces to meet the minimum performance
specified in either S5.6.1 or S5.6.2.
S5.6.7.1.2 At the level of common diaphragm leakage-type
failure (or equivalent level of leakage from the air chamber containing
that diaphragm) determined in S5.6.7.1.1, and using the following
procedure, determine the threshold maximum reservoir rate (in kPa
[psi] per minute). With an initial reservoir system pressure of 689
kPa (100 psi), the engine turned off, no application of any of
the vehicle’s brakes and, if the vehicle is designed to tow a
vehicle equipped with air brakes, a 0.819-L (50-cu. in.) test
reservoir connected to the supply line coupling, make an application
actuation of the parking brake control. Determine the maximum reservoir
leakage rate (in kPa [psi] per minute), which is the maximum
rate of decrease in air pressure of any of the vehicle’s reservoirs
that results after that parking brake application.
S5.6.7.1.3 Using the following procedure, introduce a leakage-type
failure of the common diaphragm (or equivalent leakage from the air
chamber containing that diaphragm) that results in a maximum reservoir
leakage rate that is three times the threshold maximum reservoir leakage
rate determined in S5.6.7.1.2. With an initial reservoir system pressure
of 689 kPa (100 psi), the engine turned off, no application
of any of the vehicle’s brakes and, if the vehicle is designed
to tow a vehicle equipped with air brakes, a 0.819-L (50-cu.
in.) test reservoir connected to the supply line coupling, make an
application actuation of the parking brake control. Determine the
maximum reservoir leakage rate (in kPa [psi] per minute), which
is the maximum rate of decrease in air pressure of any of the vehicle’s
reservoirs that results after that parking brake application. The
level of common diaphragm leakage-type failure (or equivalent level
of leakage from the air chamber containing that diaphragm) associated
with this reservoir leakage rate is the level that is to be used under
the option set forth in S5.6(b).
S5.6.7.2 Trailers
S5.6.7.2.1 According to the following procedure, determine
the threshold level of common diaphragm leakage-type failure (or equivalent
level of leakage from the air chamber containing that diaphragm) at
which the vehicle’s parking brakes become unreleasable. With an
initial reservoir system and supply line pressure of 689 kPa
(100 psi), no application of any of the vehicle’s brakes, and,
if the vehicle is designed to tow a vehicle equipped with air brakes,
a 0.819-L (50-cu. in.) test reservoir connected to the supply
line coupling, introduce a leakage-type failure of the common diaphragm
(or equivalent leakage from the air chamber containing that diaphragm).
Make a parking brake application by venting the front supply line
coupling to the atmosphere, and reduce the pressures in all of the
vehicle’s reservoirs to zero. Pressurize the supply line by connecting
the trailer’s front supply line coupling to the supply line portion
of the trailer test rig (Figure 1) with the
regulator of the trailer test rig set at 689 kPa (100 psi),
and determine whether all of the mechanical means referred to in S5.6.3.2
continue to be actuated and hold the parking brake applications with
sufficient parking retardation forces to meet the minimum performance
specified in either S5.6.1 or S5.6.2. Repeat this procedure with progressively
decreasing or increasing levels (whichever is applicable) of leakage-type
diaphragm failures or equivalent leakages, to determine the minimum
level of common diaphragm leakage-type failure (or equivalent level
of leakage from the air chamber containing that diaphragm) at which
all of the mechanical means referred to in S5.6.3.2 continue to be
actuated and hold the parking brake applications with sufficient parking
retardation forces to meet the minimum performance specified in either
S5.6.1 or S5.6.2.
S5.6.7.2.2 At the level of common diaphragm leakage-type
failure (or equivalent level of leakage from the air chamber containing
that diaphragm) determined in S5.6.7.2.1, and using the following
procedure, determine the threshold maximum reservoir leakage rate
(in kPa [psi] per minute). With an initial reservoir system
and supply line pressure of 689 kPa (100 psi), no application
of any of the vehicle’s brakes and, if the vehicle is designed
to tow a vehicle equipped with air brakes, a 0.819-L (50-cu.
in.) test reservoir connected to the rear supply line coupling, make
a parking brake application by venting the front supply line coupling
to the atmosphere. Determine the maximum reservoir leakage rate (in
kPa [psi] per minute), which is the maximum rate of decrease
in air pressure of any of the vehicle’s reservoirs that results
after that parking brake application.
S5.6.7.2.3 Using the following procedure, introduce
a leakage-type failure of the common diaphragm (or equivalent leakage
from the air chamber containing that diaphragm) that results in a
maximum reservoir leakage rate that is three times the threshold maximum
reservoir leakage rate determined in S5.6.7.2.2. With an initial reservoir
system and supply line pressure of 689 kPa (100 psi), no application
of any of the vehicle’s brakes and, if the vehicle is designed
to tow a vehicle equipped with air brakes, a 0.819-L (50-cu.
in.) test reservoir connected to the rear supply line coupling, make
a parking brake application by venting the front supply line coupling
to the atmosphere. Determine the maximum reservoir leakage rate (in
kPa [psi] per minute), which is the maximum rate of decrease
in air pressure of any of the vehicle’s reservoirs that results
after that parking brake application. The level of common diaphragm
leakage-type failure (or equivalent level of leakage from the air
chamber containing that diaphragm) associated with this reservoir
leakage rate is the level that is to be used under the option set
forth in S5.6(b).
S5.7 Emergency brake system for trucks
and buses
Each vehicle shall be equipped with an emergency brake system which,
under the conditions of S6.1, conforms to the requirements of S5.7.1
through S5.7.3. However, the truck portion of an auto transporter
need not meet the road test requirements of S5.7.1 and S5.7.3.
S5.7.1 Emergency brake system performance. When stopped six
times for each combination of weight and speed specified in S5.3.1.1,
except for a loaded truck tractor with an unbraked control trailer,
on a road surface having a PFC of 0.9, with a single failure in the
service brake system of a part designed to contain compressed air
or brake fluid (except failure of a common valve, manifold, brake
fluid housing, or brake chamber housing), the vehicle shall stop at
least once in not more than the distance specified in Column 5 of
Table II, measured from the point at which
movement of the service brake control begins, except that a truck
tractor tested at its unloaded vehicle mass weight plus
up to 680.4 kg (1500 pounds) shall stop at least once in not
more than the distance specified in Column 6 of Table
II. The stop shall be made without any part of the vehicle leaving
the roadway, and with unlimited wheel lockup permitted at any speed.
S5.7.2 Emergency brake system operation. The emergency brake
system shall be applied and released, and be capable of modulation,
by means of the service brake control.
S5.7.3 Towing vehicle emergency brake requirements. In addition
to meeting the other requirements of S5.7, a vehicle designed to tow
another vehicle equipped with air brakes shall:
(a) In the case of a truck tractor in the unloaded condition and
a single-unit truck which is capable of towing an air-brake-equipped
vehicle and is loaded to GVWR, be capable of meeting the requirements
of S5.7.1 by operation of the service brake control only, with the
trailer air supply line and air control line from the towing vehicle
vented to the atmosphere in accordance with S6.1.14;
(b) Be capable of modulating the air in the supply or control
line to the trailer by means of the service brake control with a
single failure in the towing vehicle’s service brake system as specified
in S5.7.1.
(c) [Reserved]
S5.8 Trailer pneumatic system failure
performance
Each trailer shall meet the requirements of S5.8.1 through S5.8.3.
S5.8.1 Emergency braking capability. Each trailer other than
a trailer converter dolly shall have a parking brake system that conforms
to S5.6 and that applies with the force specified in S5.6.1 or S5.6.2
when the air pressure in the supply line is at atmospheric pressure.
A trailer converter dolly shall have, at the manufacturer’s option,
(a) A parking brake system that conforms to S5.6 and that applies
with the force specified in S5.6.1 or S5.6.2 when the air pressure
in the supply line is at atmospheric pressure, or
(b) An emergency system that automatically applies the service
brakes when the service reservoir is at any pressure above 137.8
kPa (20 psi) and the supply line is at atmospheric pressure.
However, any agricultural commodity trailer, heavy hauler trailer,
or pulpwood trailer shall meet the requirements of S5.8.1 or, at
the option of the manufacturer, the requirements of §393.43
of Title 49 of the Code of Federal Regulations (the most
recent edition) this title.
S5.8.2 Supply line pressure retention. Any single leakage-type
failure in the service brake system (except for a failure of the supply
line, a valve directly connected to the supply line, or a component
of a brake chamber housing) shall not result in the pressure in the
supply line falling below 482.3 kPa (70 psi), as measured at
the forward trailer supply coupling. A trailer shall meet the above
supply line pressure retention requirement with its brake system connected
to the trailer test rig shown in Figure 1,
with the reservoirs of the trailer and test rig initially pressurized
to 689 kPa (100 psi) and the regulator of the trailer test
rig set at 689 kPa (100 psi), except that a trailer equipped
with an air-applied, mechanically held parking brake system and not
designed to tow a vehicle equipped with air brakes, at the manufacturer’s
option, may meet the requirements of S5.8.4 rather than those of S5.8.2
and S5.8.3.
S5.8.3 Automatic application of parking brakes. With an initial
reservoir system pressure of 689 kPa (100 psi) and an initial
supply line pressure of 689 kPa (100 psi), and if designed
to tow a vehicle equipped with air brakes, with a 0.819-L (50-cu.
in.) test reservoir connected to the rear supply line coupling, and
with any subsequent single leakage-type failure, in any other brake
system, of a part designed to contain compressed air or brake fluid
(consistent with the parenthetical phrase specified in S5.6.3.1),
whenever the air pressure in the supply line is 482.3 kPa (70
psi) or higher, the parking brakes shall not provide any brake retardation
as a result of complete or partial automatic application of the parking
brakes.
S5.8.4 Automatic application of air-applied, mechanically held
parking brakes. With its brake system connected to the supply
line portion of the trailer test rig ( Figure
1) and the regulator of the trailer test rig set at 689 kPa
(100 psi), and with any single leakage-type failure in the service
brake system (except for a failure of the supply line, a valve directly
connected to the supply line, or a component of a brake chamber, but
including failure of any common diaphragm), the parking brakes shall
not provide any brake retardation as a result of complete or partial
automatic application of the parking brakes.
S5.9 Final inspection
Inspect the service brake system for the condition of adjustment
and for the brake indicator display in accordance with S5.1.8 and
S5.2.2.
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S6. Conditions
The requirements of S5 shall be met by a vehicle when it is tested
according to the conditions set in this S6, without replacing any
brake system part or making any adjustments to the brake system except
as specified. Unless otherwise specified, where a range of conditions
is specified, the vehicle must be capable of meeting the requirements
at all points within the range. On vehicles equipped with automatic
brake adjusters, the automatic brake adjusters must remain activated
at all times. Compliance of vehicles manufactured in two or more stages
may, at the option of the final-stage manufacturer, be demonstrated
to comply with this TSD standard by adherence
to the instructions of the incomplete vehicle manufacturer provided
with the vehicle in accordance with §568.4(a)(7)(ii) and §568.5
of Title 49 of the Code of Federal Regulations (the most
recent edition).
S6.1 Road test conditions
S6.1.1 Except as otherwise specified, the vehicle is loaded to its GVWR, distributed proportionally to its GAWR. During the burnish procedure specified in S6.1.8, truck
tractors shall be loaded to their GVWR by coupling them to an unbraked flatbed semi-trailer, which semi-trailer shall be loaded so that the weight of the tractor-trailer combination
equals the GVWR of the truck tractor. The load on the unbraked flatbed semi-trailer shall be located so that the truck tractor’s wheels do not lock during burnish.
S6.1.2 The tire inflation pressure is as specified by the vehicle manufacturer for the GVWR.
S6.1.3 Unless otherwise specified, the transmission selector control is inneutral" or the clutch is disengaged during all decelerations and during static
parking brake tests.
S6.1.4 All vehicle openings (doors, windows, hood, trunk, cargo doors, etc.) are in a closed position, except as required for instrumentation purposes.
S6.1.5 The ambient temperature is between 0°C and 37.8°C (32°F and 100°F).
S6.1.6 The wind velocity is zero.
S6.1.7 Unless otherwise specified, stopping tests are conducted on a 3.66-m (12-ft.) wide level, straight roadway having a peak friction coefficient of 0.9. For road
tests in S5.3, the vehicle is aligned in the center of the roadway at the beginning of a stop. Peak friction coefficient is measured using an ASTM E1136 standard reference test tire
in accordance with ASTM method E1337-90, at a speed of 64.4 km/h (40 mph), without water delivery for the surface with PFC of 0.9, and with water delivery for the surface
with PFC of 0.5.
S6.1.8 For vehicles with parking brake systems not utilizing the service brake friction elements, burnish the friction elements of such systems prior to the parking brake
test according to the manufacturer’s recommendations. For vehicles with parking brake systems utilizing the service brake friction elements, burnish the brakes as follows: With the
transmission in the highest gear appropriate for a speed of 64.4 km/h (40 mph), make 500 snubs between 64.4 km/h (40 mph) and 32.2 km/h (20 mph) at a
deceleration rate of 3.05 m/s² (10 f.p.s.p.s.), or at the vehicle’s maximum deceleration rate if less than 3.05 m/s² (10 f.p.s.p.s.)
Except where an adjustment is specified, after each brake application accelerate to 64.4 km/h (40 mph) and maintain that speed until making the next brake application at a
point 1.6 km (1 mile) from the initial point of the previous brake application. If the vehicle cannot attain a speed of 64.4 km/h (40 mph) in 1.6 km (1 mile),
continue to accelerate until the vehicle reaches 64.4 km/h (40 mph) or until the vehicle has traveled 2.4 km (1.5 miles) from the initial point of the previous brake
application, whichever occurs first. Any automatic pressure limiting valve is in use to limit pressure as designed. The brakes may be adjusted up to three times during the burnish
procedure, at intervals specified by the vehicle manufacturer, and may be adjusted at the conclusion of the burnishing, in accordance with the vehicle manufacturer’s recommendation.
S6.1.9 Static parking brake tests for a semi-trailer are conducted with the front end supported by an unbraked dolly. The mass of the dolly is included as part of the trailer
load.
S6.1.10 In a test other than a static parking test, a truck tractor is tested at its GVWR by coupling it to an unbraked flatbed semi-trailer (hereafter, control trailer) as
specified in S6.1.10.2 to S6.1.10.4.
S6.1.10.1 [Reserved]
S6.1.10.2 The center of gravity height of the ballast on the loaded control trailer shall be less than 0.61 m (24 in.) above the top of the tractor’s fifth wheel.
S6.1.10.3 The control trailer has a single axle with a GVWR of 8 165 kg (18,000 lb.) and a length, measured from the transverse centerline of the axle to the
centerline of the kingpin, of 6.55 ± 0.15 m (258 ± 6 in.).
S6.1.10.4 The control trailer is loaded so that its axle is loaded at 2 041 kg (4,500 lb.) and the tractor is loaded to its GVWR, loaded above the kingpin only, with
the tractor’s fifth wheel adjusted so that the load on each axle measured at the tire-ground interface is nearly proportional to the axles’ respective GAWRs, without
exceeding the GAWR of the tractor’s axle, or axles, or the control trailer’s axle.
S6.1.11 Special drive conditions. A vehicle equipped with an interlocking axle system or a front-wheel drive system that is engaged and disengaged by the driver is tested
with the system disengaged.
S6.1.12 Liftable axles. A vehicle with a liftable axle is tested at GVWR with the liftable axle down and at unloaded vehicle mass weight with the
liftable axle up.
S6.1.13 Trailer test rig. The trailer test rig shown in Figure 1 is calibrated in accordance with the calibration curves shown in
Figure 3. For the requirements of S5.3.3.1 and S5.3.4.1, the pressure in the trailer test rig reservoir is initially set at 689 kPa (100 psi) for actuation
tests and 654.6 kPa (95 psi) for release tests.
S6.1.14 In testing the emergency braking system of towing vehicles under S5.7.3(a), the hose(s) is vented to the atmosphere at any time not less than 1 second and not more
than 1 minute before the emergency stop begins, while the vehicle is moving at the speed from which the stop is to be made and any manual control for the towing vehicle protection
system is in the position to supply air and brake control signals to the vehicle being towed. No brake application is made from the time the line(s) is vented until the emergency
stop begins, and no manual operation of the parking brake system or towing vehicle protection system occurs from the time the line(s) is vented until the stop is completed.
S6.1.15 Initial Brake Temperature. Unless otherwise specified, the initial brake temperature is not less than 65.6°C (150°F) and not more than
93.3°C (200°F).
S6.1.16 Thermocouples. The brake temperature is measured by plug-type thermocouples installed in the approximate center of the facing length and width of the most heavily
loaded shoe or disc pad, one per brake, as shown in Figure 2. A second thermocouple may be installed at the beginning of the test sequence if the lining
wear is expected to reach a point causing the first thermocouple to contact the rubbing surface of a drum or rotor. The second thermocouple shall be installed at a depth of 2.03
mm (0.08 in.) and located within 25.4 mm (1 in.) circumferentially of the thermocouple installed at 1.02 mm (0.04 in.) depth. For centergrooved shoes or pads,
thermocouples are installed within 3.2 mm (0.125 in.) to 6.4 mm (0.25 in.) of the groove and as close to the center as possible.
S6.1.17 Selection of compliance options. Where manufacturer options are specified, the manufacturer shall select the option by the time it certifies the vehicle and may not
thereafter select a different option for the vehicle. Each manufacturer shall, upon request from the Department of Transport National Highway Traffic Safety
Administration, provide information regarding which of the compliance options it has selected for a particular vehicle or make/model.
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S6.2 Dynamometer test conditions
S6.2.1 The dynamometer inertia for each wheel is equivalent to the load on the wheel with the axle loaded to its GAWR. For a vehicle having additional GAWRs specified for
operation at reduced speeds, the GAWR used is that specified for a speed of 80.5 km/h (50 mph), or, at the option of the manufacturer, any speed greater than 80.5 km/h
(50 mph).
S6.2.2 The ambient temperature is between 23.9°C and 37.8°C (75°F and 100°F).
S6.2.3 Air at ambient temperature is directed uniformly and continuously over the brake drum or disc at a velocity of 11.18 m/s (2,200 ft./min.).
S6.2.4 The temperature of each brake is measured by a single plug-type thermocouple installed in the center of the lining surface of the most heavily loaded shoe or pad as
shown in Figure 2. The thermocouple is outside any center groove.
S6.2.5 The rate of brake drum or disc rotation on a dynamometer corresponding to the rate of rotation on a vehicle at a given speed is calculated by assuming a tire radius
equal to the static loaded radius specified by the tire manufacturer.
S6.2.6 Brakes are burnished before testing as follows: Place the brake assembly on an inertia dynamometer and adjust the brake as recommended by the vehicle manufacturer.
Make 200 stops from 64.4 km/h (40 mph) at a deceleration of 3.05 m/s² (10 f.p.s.p.s.), with an initial brake temperature on each stop of not less than
157°C (315°F) and not more than 196°C (385°F). Make 200 additional stops from 64.4 km/h (40 mph) at a deceleration of 3.05
m/s² (10 f.p.s.p.s.) with an initial brake temperature on each stop of not less than 232°C (450°F) and not more than 288°C (550°F).
The brakes may be adjusted up to three times during the burnish procedure, at intervals specified by the vehicle manufacturer, and may be adjusted at the conclusion of the
burnishing, in accordance with the vehicle manufacturer’s recommendation.
S6.2.7 The brake temperature is increased to a specified level by conducting one or more stops from 64.4 km/h (40 mph) at a deceleration of 3.05
m/s² (10 f.p.s.p.s.). The brake temperature is decreased to a specified level by rotating the drum or disc at a constant 48.3 km/h (30 mph).
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Figure 1 — Trailer test rig
Figure 2 — Thermocouple installation
Figure 3 — Pressure vs time for 0.819-L (50-in³)
test reservoir
Table IV — [RESERVED]
Table V — Brake chamber rated
volumes
Brake
chamber type (Nominal area of piston or diaphragm in sq. in.)
| Column
1
Full stroke, cm (in.)
| Column
2
Rated volume,
L (cu. in.)
|
Type 9
| 4.45 (1.75)
/ 5.33 (2.10)
| 0.41
(25)
|
Type 12
| 4.45 (1.75)
/ 5.33 (2.10)
| 0.49
(30)
|
Type 14
| 5.72 (2.25)
/ 6.86 (2.70)
| 0.66
(40)
|
Type 16
| 5.72 (2.25)
/ 6.86 (2.70)
| 0.75
(46)
|
Type 18
| 5.72 (2.25)
/ 6.86 (2.70)
| 0.82
(50)
|
Type 20
| 5.72 (2.25)
/ 6.86 (2.70)
| 0.88
(54)
|
Type 24
| 6.35 (2.50)
/ 8.13 (3.20)
| 1.10
(67)
|
Type 30
| 6.35 (2.50)
/ 8.13 (3.20)
| 1.46
(89)
|
Type 36
| 7.62 (3.00)
/ 9.14 (3.60)
| 2.21
(135)
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ENDNOTE:
* Please see subsection
2(1) of the Motor Vehicle Safety Regulations for the applicable
definition.
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