[Code of Federal Regulations]
[Title 49, Volume 5]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR571.135]
[Page 437-457]
TITLE 49--TRANSPORTATION
CHAPTER V--NATIONAL HIGHWAY TRAFFIC
SAFETY ADMINISTRATION, DEPARTMENT
OF TRANSPORTATION
PART 571_FEDERAL MOTOR VEHICLE SAFETY STANDARDS--Table of Contents
Subpart B_Federal Motor Vehicle Safety Standards
Sec. 571.135 Standard No. 135; Passenger car brake systems.
S1. Scope. This standard specifies requirements for service brake
and associated parking brake systems.
S2. Purpose. The purpose of this standard is to ensure safe braking
performance under normal and emergency driving conditions.
S3. Application. This standard applies to passenger cars
manufactured on or after September 1, 2000 and to multi-purpose
passenger vehicles, trucks and buses with a gross vehicle weight rating
(GVWR) of 3,500 kilograms (7,716 pounds) or less, manufactured on or
after September 1, 2002. In addition, at the option of the manufacturer,
passenger cars manufactured before September 1, 2000, and multi-purpose
passenger vehicles, trucks and buses with a GVWR of 3,500 kilograms
(7,716 pounds) or less, manufactured before September 1, 2002, may meet
the requirements of this standard instead of Federal Motor Vehicle No.
105, Hydraulic Brake Systems.
S4. Definitions.
Adhesion utilization curves means curves showing, for specified load
conditions, the adhesion utilized by each axle of a vehicle plotted
against the braking ratio of the vehicle.
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 modulator
devices which adjust brake actuating forces in response to those
signals.
Backup system means a portion of a service brake system, such as a
pump,
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that automatically supplies energy in the event of a primary brake power
source failure.
Brake factor means the slope of the linear least squares regression
equation best representing the measured torque output of a brake as a
function of the measured applied line pressure during a given brake
application for which no wheel lockup occurs.
Brake hold-off pressure means the maximum applied line pressure for
which no brake torque is developed, as predicted by the pressure axis
intercept of the linear least squares regression equation best
representing the measured torque output of a brake as a function of the
measured applied line pressure during a given brake application.
Brake power assist unit means a device installed in a hydraulic
brake system that reduces the amount of muscular force that a driver
must apply to actuate the system, and that, if inoperative, does not
prevent the driver from braking the vehicle by a continued application
of muscular force on the service brake control.
Brake power unit means a device installed in a brake system that
provides the energy required to actuate the brakes, either directly or
indirectly through an auxiliary device, with driver action consisting
only of modulating the energy application level.
Braking ratio means the deceleration of the vehicle divided by the
gravitational acceleration constant.
Electric vehicle or EV means a motor vehicle that is powered by an
electric motor drawing current from rechargeable storage batteries, fuel
cells, or other portable sources of electrical current, and which may
include a non-electrical source of power designed to charge batteries
and components thereof.
Electrically-actuated service brakes means service brakes that
utilize electrical energy to actuate the foundation brakes.
Functional failure means a failure of a component (either electrical
or mechanical in nature) which renders the system totally or partially
inoperative yet the structural integrity of the system is maintained.
Hydraulic brake system means a system that uses hydraulic fluid as a
medium for transmitting force from a service brake control to the
service brake and that may incorporate a brake power assist unit, or a
brake power unit.
Initial brake temperature or IBT means the average temperature of
the service brakes on the hottest axle of the vehicle 0.32 km (0.2
miles) before any brake application.
Lightly loaded vehicle weight or LLVW means unloaded vehicle weight
plus the weight of a mass of 180 kg (396 pounds), including driver and
instrumentation.
Maximum speed of a vehicle or VMax means the highest speed
attainable by accelerating at a maximum rate from a standing start for a
distance of 3.2 km (2 miles) on a level surface, with the vehicle at its
lightly loaded vehicle weight, and, if an EV, with the propulsion
batteries at a state of charge of not less than 95 percent at the
beginning of the run.
Objective brake factor means the arithmetic average of all the brake
factors measured over the twenty brake applications defined in S7.4, for
all wheel positions having a given brake configuration.
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.
Pressure component means a brake system component that contains the
brake system fluid and controls or senses the fluid pressure.
Regenerative braking system or RBS means an electrical energy system
that is installed in an EV for recovering or dissipating kinetic energy,
and which uses the propulsion motor(s) as a retarder for partial braking
of the EV while returning electrical energy to the propulsion battery(s)
or dissipating electrical energy.
Snub means the braking deceleration of a vehicle from a higher
reference speed to a lower reference speed that is greater than zero.
Split service brake system means a brake system consisting of two or
more
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subsystems actuated by a single control, designed so that a single
failure in any subsystem (such as a leakage-type failure of a pressure
component of a hydraulic subsystem except structural failure of a
housing that is common to two or more subsystems, or an electrical
failure in an electric subsystem) does not impair the operation of any
other subsystem.
Stopping distance means the distance traveled by a vehicle from the
point of application of force to the brake control to the point at which
the vehicle reaches a full stop.
Variable brake proportioning system means a system that has one or
more proportioning devices which automatically change the brake pressure
ratio between any two or more wheels to compensate for changes in wheel
loading due to static load changes and/or dynamic weight transfer, or
due to deceleration.
Wheel lockup means 100 percent wheel slip.
S5. Equipment requirements.
S5.1. Service brake system. Each vehicle shall be equipped with a
service brake system acting on all wheels.
S5.1.1. Wear adjustment. Wear of the service brakes shall be
compensated for by means of a system of automatic adjustment.
S5.1.2. Wear status. The wear condition of all service brakes shall
be indicated by either:
(a) Acoustic or optical devices warning the driver at his or her
driving position when lining replacement is necessary, or
(b) A means of visually checking the degree of brake lining wear,
from the outside or underside of the vehicle, utilizing only the tools
or equipment normally supplied with the vehicle. The removal of wheels
is permitted for this purpose.
S5.1.3 Regenerative braking system. (a) For an EV equipped with RBS,
the RBS is considered to be part of the service brake system if it is
automatically activated by an application of the service brake control,
if there is no means provided for the driver to disconnect or otherwise
deactivate it, and if it is activated in all transmission positions,
including neutral.
(b) For an EV that is equipped with both ABS and RBS that is part of
the service brake system, the ABS must control the RBS.
S5.2. Parking brake system. Each vehicle shall be equipped with a
parking brake system of a friction type with solely mechanical means to
retain engagement.
S5.3. Controls.
S5.3.1. The service brakes shall be activated by means of a foot
control. The control of the parking brake shall be independent of the
service brake control, and may be either a hand or foot control.
S5.3.2. For vehicles equipped with ABS, a control to manually
disable the ABS, either fully or partially, is prohibited.
S5.4. Reservoirs.
S5.4.1. Master cylinder reservoirs. A master cylinder shall have a
reservoir compartment for each service brake subsystem serviced by the
master cylinder. Loss of fluid from one compartment shall not result in
a complete loss of brake fluid from another compartment.
S5.4.2. Reservoir capacity. Reservoirs, whether for master cylinders
or other type systems, shall have a total minimum capacity equivalent to
the fluid displacement resulting when all the wheel cylinders or caliper
pistons serviced by the reservoirs move from a new lining, fully
retracted position (as adjusted initially to the manufacturer's
recommended setting) to a fully worn, fully applied position, as
determined in accordance with S7.17(c) of this standard. Reservoirs
shall have completely separate compartments for each subsystem except
that in reservoir systems utilizing a portion of the reservoir for a
common supply to two or more subsystems, individual partial compartments
shall each have a minimum volume of fluid equal to at least the volume
displaced by the master cylinder piston servicing the subsystem, during
a full stroke of the piston. Each brake power unit reservoir servicing
only the brake system shall have a minimum capacity equivalent to the
fluid displacement required to charge the system piston(s) or
accumulator(s) to normal operating pressure plus the displacement
resulting when
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all the wheel cylinders or caliper pistons serviced by the reservoir or
accumulator(s) move from a new lining, fully retracted position (as
adjusted initially to the manufacturer's recommended setting) to a fully
worn, fully applied position.
S5.4.3. Reservoir labeling. Each vehicle equipped with hydraulic
brakes shall have a brake fluid warning statement that reads as follows,
in letters at least 3.2 mm (\1/8\ inch) high: ``WARNING: Clean filler
cap before removing. Use only ------ fluid from a sealed container.''
(Inserting the recommended type of brake fluid as specified in 49 CFR
571.116, e.g., ``DOT 3.'') The lettering shall be:
(a) Permanently affixed, engraved or embossed;
(b) Located so as to be visible by direct view, either on or within
100 mm (3.94 inches) of the brake fluid reservoir filler plug or cap;
and
(c) Of a color that contrasts with its background, if it is not
engraved or embossed.
S5.4.4. Fluid level indication. Brake fluid reservoirs shall be so
constructed that the level of fluid can be checked without need for the
reservoir to be opened. This requirement is deemed to have been met if
the vehicle is equipped with a transparent brake fluid reservoir or a
brake fluid level indicator meeting the requirements of S5.5.1(a)(1).
S5.5. Brake system warning indicator. Each vehicle shall have one or
more visual brake system warning indicators, mounted in front of and in
clear view of the driver, which meet the requirements of S5.5.1 through
S5.5.5. In addition, a vehicle manufactured without a split service
brake system shall be equipped with an audible warning signal that
activates under the conditions specified in S5.5.1(a).
S5.5.1. Activation. An indicator shall be activated when the
ignition (start) switch is in the ``on'' (``run'') position and whenever
any of conditions (a) through (g) occur:
(a) A gross loss of fluid or fluid pressure (such as caused by
rupture of a brake line but not by a structural failure of a housing
that is common to two or more subsystems) as indicated by one of the
following conditions (chosen at the option of the manufacturer):
(1) A drop in the level of the brake fluid in any master cylinder
reservoir compartment to less than the recommended safe level specified
by the manufacturer or to one-fourth of the fluid capacity of that
reservoir compartment, whichever is greater.
(2) For vehicles equipped with a split service brake system, a
differential pressure of 1.5 MPa (218 psi) between the intact and failed
brake subsystems measured at a master cylinder outlet or a slave
cylinder outlet.
(3) A drop in the supply pressure in a brake power unit to one-half
of the normal system pressure.
(b) Any electrical functional failure in an antilock or variable
brake proportioning system.
(c) Application of the parking brake.
(d) Brake lining wear-out, if the manufacturer has elected to use an
electrical device to provide an optical warning to meet the requirements
of S5.1.2(a).
(e) For a vehicle with electrically-actuated service brakes, failure
of the source of electric power to those brakes, or diminution of state
of charge of the batteries to less than a level specified by the
manufacturer for the purpose of warning a driver of degraded brake
performance.
(f) For a vehicle with electric transmission of the service brake
control signal, failure of a brake control circuit.
(g) For an EV with a regenerative braking system that is part of the
service brake system, failure of the RBS.
S5.5.2. Function check. (a) All indicators shall be activated as a
check function by either:
(1) Automatic activation when the ignition (start) switch is turned
to the ``on'' (``run'') position when the engine is not running, or when
the ignition (``start'') switch is in a position between ``on''
(``run'') and ``start'' that is designated by the manufacturer as a
check position, or
(2) A single manual action by the driver, such as momentary
activation of a test button or switch mounted on the instrument panel in
front of and in clear view of the driver, or, in the case of an
indicator for application of the
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parking brake, by applying the parking brake when the ignition is in the
``on'' (``run'') position.
(b) In the case of a vehicle that has an interlock device that
prevents the engine from being started under one or more conditions,
check functions meeting the requirements of S5.5.2(a) need not be
operational under any condition in which the engine cannot be started.
(c) The manufacturer shall explain the brake check function test
procedure in the owner's manual.
S5.5.3. Duration. Each indicator activated due to a condition
specified in S5.5.1 shall remain activated as long as the condition
exists, whenever the ignition (``start'') switch is in the ``on''
(``run'') position, whether or not the engine is running.
S5.5.4. Function. When a visual warning indicator is activated, it
may be continuous or flashing, except that the visual warning indicator
on a vehicle not equipped with a split service brake system shall be
flashing. The audible warning required for a vehicle manufactured
without a split service brake system may be continuous or intermittent.
S5.5.5. Labeling. (a) Each visual indicator shall display a word or
words in accordance with the requirements of Standard No. 101 (49 CFR
571.101) and this section, which shall be legible to the driver under
all daytime and nighttime conditions when activated. Unless otherwise
specified, the words shall have letters not less than 3.2 mm (\1/8\
inch) high and the letters and background shall be of contrasting
colors, one of which is red. Words or symbols in addition to those
required by Standard No. 101 and this section may be provided for
purposes of clarity.
(b) Vehicles manufactured with a split service brake system may use
a common brake warning indicator to indicate two or more of the
functions described in S5.5.1(a) through S5.5.1(d). If a common
indicator is used, it shall display the word ``Brake.''
(c) A vehicle manufactured without a split service brake system
shall use a separate indicator to indicate the failure condition in
S5.5.1(a). This indicator shall display the words ``STOP--BRAKE
FAILURE'' in block capital letters not less than 6.4 mm (\1/4\ inch) in
height.
(d) If separate indicators are used for one or more of the
conditions described in S5.5.1(a) through S5.5.1(g), the indicators
shall display the following wording:
(1) If a separate indicator is provided for the low brake fluid
condition in S5.5.1(a)(1), the words ``Brake Fluid'' shall be used
except for vehicles using hydraulic system mineral oil.
(2) If a separate indicator is provided for the gross loss of
pressure condition in S5.5.1(a)(2), the words ``Brake Pressure'' shall
be used.
(3) If a separate indicator is provided for the condition specified
in S5.5.1(b), the letters and background shall be of contrasting colors,
one of which is yellow. The indicator shall be labeled with the words
``Antilock'' or ``Anti-lock'' or ``ABS''; or ``Brake Proportioning,'' in
accordance with Table 2 of Standard No. 101.
(4) If a separate indicator is provided for application of the
parking brake as specified for S5.5.1(c), the single word ``Park'' or
the words ``Parking Brake'' may be used.
(5) If a separate indicator is provided to indicate brake lining
wear-out as specified in S5.5.1(d), the words ``Brake Wear'' shall be
used.
(6) If a separate indicator is provided for the condition specified
in S5.5.1(g), the letters and background shall be of contrasting colors,
one of which is yellow. The indicator shall be labeled with the symbol
``RBS.'' RBS failure in a system that is part of the service brake
system may also be indicated by a yellow lamp that also indicates
``ABS'' failure and displays the symbol ``ABS/RBS.''
(7) If a separate indicator is provided for any other function, the
display shall include the word ``Brake'' and the appropriate additional
labeling.
S5.6. Brake system integrity. Each vehicle shall meet the complete
performance requirements of this standard without:
(a) Detachment or fracture of any component of the braking system,
such as brake springs and brake shoes or disc pad facings other than
minor cracks that do not impair attachment of the friction facings. All
mechanical
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components of the braking system shall be intact and functional.
Friction facing tearout (complete detachment of lining) shall not exceed
10 percent of the lining on any single frictional element.
(b) Any visible brake fluid or lubricant on the friction surface of
the brake, or leakage at the master cylinder or brake power unit
reservoir cover, seal, and filler openings.
S6. General test conditions. Each vehicle must meet the performance
requirements specified in S7 under the following test conditions and in
accordance with the test procedures and test sequence specified. Where a
range of conditions is specified, the vehicle must meet the requirements
at all points within the range.
S6.1. Ambient conditions.
S6.1.1. Ambient temperature. The ambient temperature is any
temperature between 0 [deg]C (32 [deg]F) and 40 [deg]C (104 [deg]F).
S6.1.2. Wind speed. The wind speed is not greater than 5 m/s (11.2
mph).
S6.2. Road test surface.
S6.2.1. Pavement friction. Unless otherwise specified, the road test
surface produces a peak friction coefficient (PFC) of 0.9 when measured
using an American Society for Testing and Materials (ASTM) E1136
standard reference test tire, in accordance with ASTM Method E 1337-90,
at a speed of 64.4 km/h (40 mph), without water delivery.
S6.2.2. Gradient. Except for the parking brake gradient holding
test, the test surface has no more than a 1% gradient in the direction
of testing and no more than a 2% gradient perpendicular to the direction
of testing.
S6.2.3. Lane width. Road tests are conducted on a test lane 3.5 m
(11.5 ft) wide.
S6.3. Vehicle conditions.
S6.3.1. Vehicle weight.
S6.3.1.1. For the tests at GVWR, the vehicle is loaded to its GVWR
such that the weight on each axle as measured at the tire-ground
interface is in proportion to its GAWR, with the fuel tank filled to
100% of capacity. However, if the weight on any axle of a vehicle at
LLVW exceeds the axle's proportional share of the GVWR, the load
required to reach GVWR is placed so that the weight on that axle remains
the same as at LLVW.
S6.3.1.2. For the test at LLVW, the vehicle is loaded to its LLVW
such that the added weight is distributed in the front passenger seat
area.
S6.3.2. Fuel tank loading. The fuel tank is filled to 100% of
capacity at the beginning of testing and may not be less than 75% of
capacity during any part of the testing.
S6.3.3. Lining preparation. At the beginning of preparation for the
road tests, the brakes of the vehicle are in the same condition as when
the vehicle was manufactured. No burnishing or other special preparation
is allowed, unless all vehicles sold to the public are similarly
prepared as a part of the manufacturing process.
S6.3.4. Adjustments and repairs. These requirements must be met
without replacing any brake system parts or making any adjustments to
the brake system except as specified in this standard. Where brake
adjustments are specified (S7.1.3), adjust the brakes, including the
parking brakes, in accordance with the manufacturer's recommendation. No
brake adjustments are allowed during or between subsequent tests in the
test sequence.
S6.3.5. Automatic brake adjusters. Automatic adjusters are
operational throughout the entire test sequence. They may be adjusted
either manually or by other means, as recommended by the manufacturer,
only prior to the beginning of the road test sequence.
S6.3.6. Antilock brake system (ABS). If a car is equipped with an
ABS, the ABS is fully operational for all tests, except where specified
in the following sections.
S6.3.7. Variable brake proportioning valve. If a car is equipped
with a variable brake proportioning system, the proportioning valve is
fully operational for all tests except the test for failed variable
brake proportioning system.
S6.3.8. Tire inflation pressure. Tires are inflated to the pressure
recommended by the vehicle manufacturer for the GVWR of the vehicle.
S6.3.9. Engine. Engine idle speed and ignition timing are set
according to the manufacturer's recommendations.
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If the vehicle is equipped with an adjustable engine speed governor, it
is adjusted according to the manufacturer's recommendations.
S6.3.10. Vehicle openings. All vehicle openings (doors, windows,
hood, trunk, convertible top, cargo doors, etc.) are closed except as
required for instrumentation purposes.
S6.3.11 State of charge of batteries for EVs.
S6.3.11.1 The state of charge of the propulsion batteries is
determined in accordance with SAE Recommended Practice J227a, Electric
Vehicle Test Procedure, February 1976. The applicable sections of J227a
are 3.2.1 through 3.2.4, 3.3.1 through 3.3.2.2, 3.4.1 and 3.4.2, 4.2.1,
5.2, 5.2.1 and 5.3.
S6.3.11.2 At the beginning of the burnish procedure (S7.1 of this
standard) in the test sequence, each propulsion battery is at the
maximum state of charge recommended by the manufacturer, as stated in
the vehicle operator's manual or on a label that is permanently attached
to the vehicle, of, if the manufacturer has made no recommendation, not
less than 95 percent. During the 200-stop burnish procedure, the
propulsion batteries are restored to the maximum state of charge
determined as above, after each increment of 40 burnish stops until the
burnish procedure is complete. The batteries may be charged at a more
frequent interval during a particular 40-stop increment only if the EV
is incapable of achieving the initial burnish test speed during that
increment. During the burnish procedure, the propulsion batteries may be
charged by external means or replaced by batteries that are at a state
of charge of not less than 95 percent. For an EV having a manual control
for setting the level of regenerative braking, the manual control, at
the beginning of the burnish procedure, is set to provide maximum
regenerative braking throughout the burnish.
S6.3.11.3 At the beginning of each performance test in the test
sequence (S7.2 through S7.17 of this standard), unless otherwise
specified, an EV's propulsion batteries are at the state of charge
recommended by the manufacturer, as stated in the vehicle operator's
manual or on a label that is permanently attached to the vehicle, or, if
the manufacturer has made no recommendation, at a state of charge of not
less than 95 percent. No further charging of any propulsion battery
occurs during any of the performance tests in the test sequence of this
standard. If the propulsion batteries are depleted during a test
sequence such that the vehicle reaches automatic shut-down, will not
accelerate, or the low state of charge brake warning lamp is
illuminated, the vehicle is to be accelerated to brake test speed by
auxiliary means. If a battery is replaced rather than recharged, the
replacement battery shall be charged and measured for state of charge in
accordance with these procedures.
S6.3.12 State of charge of batteries for electrically-actuated
service brakes. A vehicle equipped with electrically-actuated service
brakes also performs the following test series. Conduct 10 stopping
tests from a speed of 100 kph or the maximum vehicle speed, whichever is
less. At least two of the 10 stopping distances must be less than or
equal to 70 meters. The vehicle is loaded to GVWR and the transmission
is in the neutral position when the service brake control is actuated
and throughout the remainder of the test. Each battery providing power
to the electrically-actuated service brakes, shall be in a depleted
state of charge for conditions (a), (b), or (c) of this paragraph as
appropriate. An auxiliary means may be used to accelerate an EV to test
speed.
(a) For an EV equipped with electrically-actuated service brakes
deriving power from the propulsion batteries and with automatic shut-
down capability of the propulsion motor(s), the propulsion batteries are
at not more than five percent above the EV actual automatic shut-down
critical value. The critical value is determined by measuring the state-
of-charge of each propulsion battery at the instant that automatic shut-
down occurs.
(b) For an EV equipped with electrically-actuated service brakes
deriving power from the propulsion batteries and with no automatic shut-
down capability of the propulsion motor(s), the propulsion batteries are
at an average of not more than five percent above the actual state of
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charge at which the brake failure warning signal, required by S5.5.1(e)
of this standard, is illuminated.
(c) For a vehicle which has one or more auxiliary batteries that
provides electrical energy to operate the electrically-actuated service
brakes, each auxiliary battery is at not more than five percent above
the actual state of charge at which the brake failure warning signal,
required by S5.5.1(e) of this standard, is illuminated.
S6.3.13 Electric vehicles.
S6.3.13.1 (a) For an EV equipped with an RBS that is part of the
service brake system, the RBS is operational during the burnish and all
tests, except for the test of a failed RBS.
(b) For an EV equipped with an RBS that is not part of the service
brake system, the RBS is operational and set to produce the maximum
regenerative braking effect during the burnish, and is disabled during
the test procedures. If the vehicle is equipped with a neutral gear that
automatically disables the RBS, the test procedures which are designated
to be conducted in gear may be conducted in neutral.
S6.3.13.2 For tests conducted ``in neutral'', the operator of an EV
with no ``neutral'' position (or other means such as a clutch for
disconnecting the drive train from the propulsion motor(s)) does not
apply any electromotive force to the propulsion motor(s). Any
electromotive force that is applied to the propulsion motor(s)
automatically remains in effect unless otherwise specified by the test
procedure.
S6.4. Instrumentation.
S6.4.1. Brake temperature measurement. 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 1. 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
metal rubbing surface of a drum or rotor. For center-grooved shoes or
pads, thermocouples are installed within 3 mm (.12 in) to 6 mm (.24 in)
of the groove and as close to the center as possible.
S6.4.2. Brake line pressure measurement for the torque wheel test.
The vehicle shall be fitted with pressure transducers in each hydraulic
circuit. On hydraulically proportioned circuits, the pressure transducer
shall be downstream of the operative proportioning valve.
S6.4.3. Brake torque measurement for the torque wheel test. The
vehicle shall be fitted with torque wheels at each wheel position,
including slip ring assemblies and wheel speed indicators to permit
wheel lock to be detected.
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[GRAPHIC] [TIFF OMITTED] TC01AU91.070
S6.5. Procedural conditions.
S6.5.1. Brake control. All service brake system performance
requirements, including the partial system requirements of S7.7, S7.10
and S7.11, must be met solely by use of the service brake control.
S6.5.2. Test speeds. If a vehicle is incapable of attaining the
specified normal test speed, it is tested at a speed that is a multiple
of 5 km/h (3.1 mph) that is 4 to 8 km/h (2.5 to 5.0 mph) less than its
maximum speed and its performance must be within a stopping distance
given by the formula provided for the specific requirement.
S6.5.3. Stopping distance.
S6.5.3.1. The braking performance of a vehicle is determined by
measuring the stopping distance from a given initial speed.
S6.5.3.2. Unless otherwise specified, the vehicle is stopped in the
shortest distance achievable (best effort) on all stops. Where more than
one stop is required for a given set of test conditions, a vehicle is
deemed to comply with the corresponding stopping distance requirements
if at least one of the stops is made within the prescribed distance.
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S6.5.3.3. In the stopping distance formulas given for each
applicable test (such as S<=0.10V+0.0060V2), S is the maximum
stopping distance in meters, and V is the test speed in km/h.
S6.5.4. Vehicle position and attitude.
S6.5.4.1. The vehicle is aligned in the center of the lane at the
start of each brake application. Steering corrections are permitted
during each stop.
S6.5.4.2. Stops are made without any part of the vehicle leaving the
lane and without rotation of the vehicle about its vertical axis of more
than 15[deg] from the center line of the test lane
at any time during any stop.
S6.5.5. Transmission selector control.
S6.5.5.1. For tests in neutral, a stop or snub is made in accordance
with the following procedures:
(a) Exceed the test speed by 6 to 12 km/h (3.7 to 7.5 mph);
(b) Close the throttle and coast in gear to approximately 3 km/h
(1.9 mph) above the test speed;
(c) Shift to neutral; and
(d) When the test speed is reached, apply the brakes.
S6.5.5.2. For tests in gear, a stop or snub is made in accordance
with the following procedures:
(a) With the transmission selector in the control position
recommended by the manufacturer for driving on a level surface at the
applicable test speed, exceed the test speed by 6 to 12 km/h (3.7 to 7.5
mph);
(b) Close the throttle and coast in gear; and
(c) When the test speed is reached apply the brakes.
(d) To avoid engine stall, a manual transmission may be shifted to
neutral (or the clutch disengaged) when the vehicle speed is below 30
km/h (18.6 mph).
S6.5.6. Initial brake temperature (IBT). If the lower limit of the
specified IBT for the first stop in a test sequence (other than a
parking brake grade holding test) has not been reached, the brakes are
heated to the IBT by making one or more brake applications from a speed
of 50 km/h (31.1 mph), at a deceleration rate not greater than 3 m/s\2\
(9.8 fps\2\).
S7. Road test procedures and performance requirements. Each vehicle
shall meet all the applicable requirements of this section, when tested
according to the conditions and procedures set forth below and in S6, in
the sequence specified in Table 1:
Table 1--Road Test Sequence
------------------------------------------------------------------------
Section
Testing order No.
------------------------------------------------------------------------
Vehicle loaded to GVWR:
1 Burnish.................................................. S7.1
2 Wheel lock sequence...................................... S7.2
Vehicle loaded to LLVW:
3 Wheel lock sequence...................................... S7.2
4 ABS performance.......................................... S7.3
5 Torque wheel............................................. S7.4
Vehicle loaded to GVWR:
6 Torque wheel............................................. S7.4
7 Cold effectiveness....................................... S7.5
8 High speed effectiveness................................. S7.6
9 Stops with engine off.................................... S7.7
Vehicle loaded to LLVW:
10 Cold effectiveness...................................... S7.5
11 High speed effectiveness................................ S7.6
12 Failed antilock......................................... S7.8
13 Failed proportioning valve.............................. S7.9
14 Hydraulic circuit failure............................... S7.10
Vehicle loaded to GVWR:
15 Hydraulic circuit failure............................... S7.10
16 Failed antilock......................................... S7.8
17 Failed proportioning valve.............................. S7.9
18 Power brake unit failure................................ S7.11
19 Parking brake........................................... S7.12
20 Heating Snubs........................................... S7.13
21 Hot Performance......................................... S7.14
22 Brake cooling........................................... S7.15
23 Recovery Performance.................................... S7.16
24 Final Inspection........................................ S7.17
------------------------------------------------------------------------
S7.1. Burnish.
S7.1.1. General information. Any pretest instrumentation checks are
conducted as part of the burnish procedure, including any necessary
rechecks after instrumentation repair, replacement or adjustment.
Instrumentation check test conditions must be in accordance with the
burnish test procedure specified in S7.1.2 and S7.1.3.
S7.1.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In gear.
S7.1.3. Test conditions and procedures. The road test surface
conditions specified in S6.2 do not apply to the burnish procedure.
(a) IBT: <=100 [deg]C (212 [deg]F).
(b) Test speed: 80 km/h (49.7 mph).
(c) Pedal force: Adjust as necessary to maintain specified constant
deceleration rate.
(d) Deceleration rate: Maintain a constant deceleration rate of 3.0
m/s\2\ (9.8 fps\2\).
[[Page 447]]
(e) Wheel lockup: No lockup of any wheel allowed for longer than 0.1
seconds at speeds greater than 15 km/h (9.3 mph).
(f) Number of runs: 200 stops.
(g) Interval between runs: The interval from the start of one
service brake application to the start of the next is either the time
necessary to reduce the IBT to 100 [deg]C (212 [deg]F) or less, or the
distance of 2 km (1.24 miles), whichever occurs first.
(h) Accelerate to 80 km/h (49.7 mph) after each stop and maintain
that speed until making the next stop.
(i) After burnishing, adjust the brakes as specified in S6.3.4.
S7.2 Wheel lockup sequence.
S7.2.1 General information. (a) The purpose of this test is to
ensure that lockup of both front wheels occurs either simultaneously
with, or at a lower deceleration rate than, the lockup of both rear
wheels, when tested on road surfaces affording adhesion such that wheel
lockup of the first axle occurs at a braking ratio of between 0.15 and
0.80, inclusive.
(b) This test is for vehicles without antilock brake systems.
(c) This wheel lock sequence test is to be used as a screening test
to evaluate a vehicle's axle lockup sequence and to determine whether
the torque wheel test in S7.4 must be conducted.
(d) For this test, a simultaneous lockup of the front and rear
wheels refers to the conditions when the time interval between the first
occurrence of lockup of the last (second) wheel on the rear axle and the
first occurrence of lockup of the last (second) wheel on the front axle
is <= 0.1 second for vehicle speeds 15 km/h (9.3 mph).
(e) A front or rear axle lockup is defined as the point in time when
the last (second) wheel on an axle locks up.
(f) Vehicles that lock their front axle simultaneously or at lower
deceleration rates than their rear axle need not be tested to the torque
wheel procedure.
(g) Vehicles which lock their rear axle at deceleration rates lower
than the front axle shall also be tested in accordance with the torque
wheel procedure in S7.4.
(h) Any determination of noncompliance for failing adhesion
utilization requirements shall be based on torque wheel test results.
S7.2.2 Vehicle conditions. (a) Vehicle load: GVWR and LLVW.
(b) Transmission position: In neutral.
S7.2.3. Test Conditions and Procedures. (a) IBT: <=65 [deg]C (149
[deg]F), <=100 [deg]C (212 [deg]F).
(b) Test speed: 65 km/h (40.4 mph) for a braking ratio <= 0.50; 100
km/h (62.1 mph) for a braking ratio 0.50.
(c) Pedal force:
(1) Pedal force is applied and controlled by the vehicle driver or
by a mechanical brake pedal actuator.
(2) Pedal force is increased at a linear rate such that the first
axle lockup occurs no less than one-half (0.5) second and no more than
one and one-half (1.5) seconds after the initial application of the
pedal.
(3) The pedal is released when the second axle locks, or when the
pedal force reaches 1kN (225 lbs), or 0.1 seconds after first axle
lockup, whichever occurs first.
(d) Wheel lockup: Only wheel lockups above a vehicle speed of 15 km/
h (9.3 mph) are considered in determining the results of this test.
(e) Test surfaces: This test is conducted, for each loading
condition, on two different test surfaces that will result in a braking
ratio of between 0.15 and 0.80, inclusive. NHTSA reserves the right to
choose the test surfaces to be used based on adhesion utilization curves
or any other method of determining ``worst case'' conditions.
(f) The data recording equipment shall have a minimum sampling rate
of 40 Hz.
(g) Data to be recorded. The following information must be
automatically recorded in phase continuously throughout each test run
such that values of the variables can be cross referenced in real time.
(1) Vehicle speed.
(2) Brake pedal force.
(3) Angular velocity at each wheel.
(4) Actual instantaneous vehicle deceleration or the deceleration
calculated by differentiation of the vehicle speed.
(h) Speed channel filtration. For analog instrumentation, the speed
channel shall be filtered by using a low-pass filter having a cut-off
frequency of less than one fourth the sampling rate.
[[Page 448]]
(i) Test procedure. For each test surface, three runs meeting the
pedal force application and time for wheel lockup requirements shall be
made. Up to a total of six runs will be allowed to obtain three valid
runs. Only the first three valid runs obtained shall be used for data
analysis purposes.
S7.2.4. Performance requirements. (a) In order to pass this test a
vehicle shall be capable of meeting the test requirements on all test
surfaces that will result in a braking ratio of between 0.15 and 0.80,
inclusive.
(b) If all three valid runs on each surface result in the front axle
locking before or simultaneously with the rear axle, or the front axle
locks up with only one or no wheels locking on the rear axle, the torque
wheel procedure need not be run, and the vehicle is considered to meet
the adhesion utilization requirements of this Standard. This performance
requirement shall be met for all vehicle braking ratios between 0.15 and
0.80.
(c) If any one of the three valid runs on any surface results in the
rear axle locking before the front axle or the rear axle locks up with
only one or no wheels locking on the front axle the torque wheel
procedure shall be performed. This performance requirement shall be met
for all vehicle braking ratios between 0.15 and 0.80.
(d) If any one of the three valid runs on any surface results in
neither axle locking (i.e., only one or no wheels locked on each axle)
before a pedal force of 1kN (225 lbs) is reached, the vehicle shall be
tested to the torque wheel procedure.
(e) If the conditions listed in paragraph (c) or (d) of this section
occur, vehicle compliance shall be determined from the results of a
torquesults of a torque wheel test performed in accordance with S7.4.
(f) An EV with RBS that is part of the service brake system shall
meet the performance requirements over the entire normal operating range
of the RBS.
S7.3. ABS performance. [Reserved]
S7.4. Adhesion utilization (Torque Wheel Method).
S7.4.1. General information. This test is for vehicles without any
ABS. The purpose of the test is to determine the adhesion utilization of
a vehicle.
S7.4.2. Vehicle conditions. (a) Vehicle load: GVWR and LLVW.
(b) Transmission position: In neutral.
(c) Tires: For this test, a separate set of tires, identical to
those used for all other tests under Section 7.0, may be used.
S7.4.3. Test conditions and procedures. (a) IBT: <=65 [deg]C (149
[deg]F), <=100 [deg]C (212 [deg]F).
(b) Test speeds: 100 km/h (62.1 mph), and 50 km/h (31.1 mph).
(c) Pedal force: Pedal force is increased at a linear rate between
100 and 150 N/sec (22.5 and 33.7 lbs/sec) for the 100 km/h test speed,
or between 100 and 200 N/sec (22.5 and 45.0 lbs/sec) for the 50 km/h
test speed, until the first axle locks or until a pedal force of 1 kN
(225 lbs) is reached, whichever occurs first.
(d) Cooling: Between brake applications, the vehicle is driven at
speeds up to 100 km/h (62.1 mph) until the IBT specified in S7.4.3(a) is
reached.
(e) Number of runs: With the vehicle at LLVW, run five stops from a
speed of 100 km/h (62.1 mph) and five stops from a speed of 50 km/h
(31.1 mph), while alternating between the two test speeds after each
stop. With the vehicle at GVWR, repeat the five stops at each test speed
while alternating between the two test speeds.
(f) Test surface: PFC of at least 0.9.
(g) Data to be recorded. The following information must be
automatically recorded in phase continuously throughout each test run
such that values of the variables can be cross referenced in real time:
(1) Vehicle speed.
(2) Brake pedal force.
(3) Angular velocity at each wheel.
(4) Brake torque at each wheel.
(5) Hydraulic brake line pressure in each brake circuit.
Hydraulically proportioned circuits shall be fitted with transducers on
at least one front wheel and one rear wheel downstream of the operative
proportioning or pressure limiting valve(s).
(6) Vehicle deceleration.
(h) Sample rate: All data acquisition and recording equipment shall
support a minimum sample rate of 40 Hz on all channels.
(i) Determination of front versus rear brake pressure. Determine the
front
[[Page 449]]
versus rear brake pressure relationship over the entire range of line
pressures. Unless the vehicle has a variable brake proportioning system,
this determination is made by static test. If the vehicle has a variable
brake proportioning system, dynamic tests are run with the vehicle both
empty and loaded. 15 snubs from 50 km/h (31.1 mph) are made for each of
the two load conditions, using the same initial conditions specified in
this section.
S7.4.4. Data reduction. (a) The data from each brake application
under S7.4.3 is filtered using a five-point, on-center moving average
for each data channel.
(b) For each brake application under S7.4.3 determine the slope
(brake factor) and pressure axis intercept (brake hold-off pressure) of
the linear least squares equation best describing the measured torque
output at each braked wheel as a function of measured line pressure
applied at the same wheel. Only torque output values obtained from data
collected when the vehicle deceleration is within the range of 0.15g to
0.80g are used in the regression analysis.
(c) Average the results of paragraph (b) of this section to
calculate the average brake factor and brake hold-off pressure for all
brake applications for the front axle.
(d) Average the results of paragraph (b) of this section to
calculate the average brake factor and brake hold-off pressure for all
brake applications for the rear axle.
(e) Using the relationship between front and rear brake line
pressure determined in S7.4.3(i) and the tire rolling radius, calculate
the braking force at each axle as a function of front brake line
pressure.
(f) Calculate the braking ratio of the vehicle as a function of the
front brake line pressure using the following equation:
[GRAPHIC] [TIFF OMITTED] TC01AU91.071
where z = braking ratio at a given front line pressure;
T1, T2 = Braking forces at the front and rear
axles, respectively, corresponding to the same front brake line
pressure, and
P = total vehicle weight.
(g) Calculate the adhesion utilized at each axle as a function of
braking ratio using the following equations:
[GRAPHIC] [TIFF OMITTED] TR02FE95.014
where fi = adhesion utilized by axle i
Ti = braking force at axle i (from (e))
Pi = static weight on axle i
i = 1 for the front axle, or 2 for the rear axle
z = braking ratio (from (f))
h = height of center of gravity of the vehicle
P = total vehicle weight
E = wheelbase
(h) Plot f1 and f2 obtained in (g) as a
function of z, for both GVWR and LLVW load conditions. These are the
adhesion utilization curves for the vehicle, which are compared to the
performance requirements in S7.4.5. shown graphically in Figure 2:
[[Page 450]]
[GRAPHIC] [TIFF OMITTED] TC01AU91.072
S7.4.5. Performance requirements. For all braking ratios between
0.15 and 0.80, each adhesion utilization curve for a rear axle shall be
situated below a line defined by z=0.9k where z is the braking ratio and
k is the PFC.
S7.4.5.1 An EV with RBS that is part of the service brake system
shall meet the performance requirement over the entire normal operating
range of the RBS.
S7.5. Cold effectiveness.
S7.5.1. Vehicle conditions. (a) Vehicle load: GVWR and LLVW.
(b) Transmission position: In neutral.
S7.5.2. Test conditions and procedures. (a) IBT: <=65 [deg]C (149
[deg]F), <=100 [deg]C (212 [deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: <=65N (14.6 lbs), <=500N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds
allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 0.9.
(g) For each stop, bring the vehicle to test speed and then stop the
vehicle in the shortest possible distance under the specified
conditions.
[[Page 451]]
S7.5.3. Performance requirements. (a) Stopping distance for 100 km/h
test speed: <=70m (230 ft).
(b) Stopping distance for reduced test speed: S<=0.10V+0.0060V\2\.
S7.6. High speed effectiveness. This test is not run if vehicle
maximum speed is less than or equal to 125 km/h (77.7 mph).
S7.6.1. Vehicle conditions. (a) Vehicle load: GVWR and LLVW.
(b) Transmission position: In gear.
S7.6.2. Test conditions and procedures. (a) IBT: <=65 [deg]C (149
[deg]F), <=100 [deg]C (212 [deg]F).
(b) Test speed: 80% of vehicle maximum speed if 125 km/h (77.7 mph)
< vehicle maximum speed < 200 km/h (124.3 mph), or 160 km/h (99.4 mph)
if vehicle maximum speed <= 200 km/h (124.3 mph).
(c) Pedal force: <=65N (14.6 lbs), <=500N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds
allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 0.9.
S7.6.3. Performance requirements.
Stopping distance: S<=0.10V+0.0067V\2\.
S7.7. Stops with Engine Off.
S7.7.1. General information. This test is for vehicles equipped with
one or more brake power units or brake power assist units. This test is
also for EVs.
S7.7.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
(c) Vehicle engine: Off (not running).
(d) Ignition key position: May be returned to ``on'' position after
turning engine off, or a device may be used to ``kill'' the engine while
leaving the ignition key in the ``on'' position.
S7.7.3. Test conditions and procedures. (a) IBT: <=65 [deg]C (149
[deg]F), <=100 [deg]C (212 [deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: <=65N (14.6 lbs), <=500N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel allowed for longer than 0.1
seconds at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 0.9.
(g) All system reservoirs (brake power and/or assist units) are
fully charged and the vehicle's engine is off (not running) at the
beginning of each stop.
(h) For an EV, this test is conducted with no electrical power
supplied to the vehicle's propulsion motor(s), but with the RBS and
brake power or power assist still operating, unless cutting off the
supply of electrical power to the propulsion motor(s) also disables
those systems.
S7.7.4. Performance requirements. (a) Stopping distance for 100 km/h
test speed: <=70m (230 ft.)
(b) Stopping distance for reduced test speed: S <= 0.10V +
0.0060V\2\.
S7.8. Antilock functional failure.
S7.8.1. Vehicle conditions. (a) Vehicle loading: LLVW and GVWR.
(b) Transmission position: In neutral.
S7.8.2. Test conditions and procedures. (a) IBT: <=65 [deg]C (149
[deg]F), <=100 [deg]C (212 [deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: <= 65 N (14.6 lbs), <= 500 N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for more than 0.1 seconds
allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 0.9.
(g) Functional failure simulation:
(1) Disconnect the functional power source, or any other electrical
connector that creates a functional failure.
(2) Determine whether the brake system indicator is activated when
any electrical functional failure of the antilock system is created.
(3) Restore the system to normal at the completion of this test.
(h) If more than one antilock brake subsystem is provided, repeat
test for each subsystem.
S7.8.3. Performance requirements. For service brakes on a vehicle
equipped with one or more antilock systems, in the event of any single
functional failure in any such system, the service brake system shall
continue to operate and shall stop the vehicle as specified in S7.8.3(a)
or S7.8.3(b).
(a) Stopping distance for 100 km/h test speed: <= 85 m (279 ft).
(b) Stopping distance for reduced test speed: S <= 0.10V +
0.0075V\2\.
S7.9. Variable brake proportioning system functional failure.
S7.9.1. Vehicle conditions. (a) Vehicle load: LLVW and GVWR.
(b) Transmission position: In neutral.
[[Page 452]]
S7.9.2. Test conditions and procedures. (a) IBT: <=65 [deg]C (149
[deg]F), <=100 [deg]C (212 [deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: <= 65 N (14.6 lbs), <= 500 N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds
allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 0.9.
(g) Functional failure simulation:
(1) Disconnect the functional power source or mechanical linkage to
render the variable brake proportioning system inoperative.
(2) If the system utilizes electrical components, determine whether
the brake system indicator is activated when any electrical functional
failure of the variable proportioning system is created.
(3) Restore the system to normal at the completion of this test.
(h) If more than one variable brake proportioning subsystem is
provided, repeat the test for each subsystem.
S7.9.3. Performance requirements. The service brakes on a vehicle
equipped with one or more variable brake proportioning systems, in the
event of any single functional failure in any such system, shall
continue to operate and shall stop the vehicle as specified in S7.9.3(a)
or S7.9.3(b).
(a) Stopping distance for 100 km/h test speed: <= 110 m (361 ft).
(b) Stopping distance for reduced test speed: S <=0.10V +
0.0100V\2\.
S7.10. Hydraulic circuit failure.
S7.10.1. General information. This test is for vehicles manufactured
with or without a split service brake system.
S7.10.2. Vehicle conditions. (a) Vehicle load: LLVW and GVWR.
(b) Transmission position: In neutral.
S7.10.3. Test conditions and procedures. (a) IBT: <=65 [deg]C (149
[deg]F), <=100 [deg]C (212 [deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: <=65N (14.6 lbs), <=500 N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds
allowed at speeds greater than 15 km/h (9.3 mph).
(e) Test surface: PFC of 0.9.
(f) Alter the service brake system to produce any single failure.
For a hydraulic circuit, this may be any single rupture or leakage type
failure, other than a structural failure of a housing that is common to
two or more subsystems. For a vehicle in which the brake signal is
transmitted electrically between the brake pedal and some or all of the
foundation brakes, regardless of the means of actuation of the
foundation brakes, this may be any single failure in any circuit that
electrically transmits the brake signal. For an EV with RBS that is part
of the service brake system, this may be any single failure in the RBS.
(g) Determine the control force pressure level or fluid level (as
appropriate for the indicator being tested) necessary to activate the
brake warning indicator.
(h) Number of runs: After the brake warning indicator has been
activated, make the following stops depending on the type of brake
system:
(1) 4 stops for a split service brake system.
(2) 10 consecutive stops for a non-split service brake system.
(i) Each stop is made by a continuous application of the service
brake control.
(j) Restore the service brake system to normal at the completion of
this test.
(k) Repeat the entire sequence for each of the other subsystems.
S7.10.4 Performance requirements. For vehicles manufactured with a
split service brake system, in the event of any failure in a single
subsystem, as specified in S7.10.3(f) of this standard, and after
activation of the brake system indicator as specified in S5.5.1, the
remaining portions of the service brake system shall continue to operate
and shall stop the vehicle as specified in S7.10.4(a) or S7.10.4(b). For
vehicles not manufactured with a split service brake system, in the
event of any failure in any component of the service brake system, as
specified in S7.10.3(f), and after activation of the brake system
indicator as specified in S5.5.1 of this standard, the vehicle shall, by
operation of the service brake control, stop 10 times consecutively as
specified in S7.10.4(a) or S7.10.4(b).
(a) Stopping distance from 100 km/h test speed: <= 168 m (551 ft).
[[Page 453]]
(b) Stopping distance for reduced test speed: S <= 0.10V +
0.0158V2.
S7.11. Brake power unit or brake power assist unit inoperative
(System depleted).
S7.11.1. General information. This test is for vehicles equipped
with one or more brake power units or brake power assist units.
S7.11.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
S7.11.3. Test conditions and procedures. (a) IBT: <=65 [deg]C (149
[deg]F), <=100 [deg]C (212 [deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: <= 65 N (14.6 lbs), <= 500 N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds
allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 0.9.
(g) Disconnect the primary source of power for one brake power
assist unit or brake power unit, or one of the brake power unit or brake
power assist unit subsystems if two or more subsystems are provided.
(h) If the brake power unit or power assist unit operates in
conjunction with a backup system and the backup system is automatically
activated in the event of a primary power service failure, the backup
system is operative during this test.
(i) Exhaust any residual brake power reserve capability of the
disconnected system.
(j) Make each of the 6 stops by a continuous application of the
service brake control.
(k) Restore the system to normal at completion of this test.
(l) For vehicles equipped with more than one brake power unit or
brake power assist unit, conduct tests for each in turn.
(m) For vehicles with electrically-actuated service brakes (brake
power unit), this test is conducted with any single electrical failure
in the electrically-actuated service brakes instead of a failure of any
other brake power or brake power assist unit, and all other systems
intact.
S7.11.4. Performance requirements. The service brakes on a vehicle
equipped with one or more brake power assist units or brake power units,
with one such unit inoperative and depleted of all reserve capability,
shall stop the vehicle as specified in S7.11.4(a) or S7.11.4(b).
(a) Stopping distance from 100 km/h test speed: <= 168 m (551 ft).
(b) Stopping distance for reduced test speed: S <= 0.10V +
0.0158V2.
S7.12. Parking brake.
S7.12.1. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
(c) Parking brake burnish:
(1) For vehicles with parking brake systems not utilizing the
service friction elements, the friction elements of such a system are
burnished prior to the parking brake test according to the published
recommendations furnished to the purchaser by the manufacturer.
(2) If no recommendations are furnished, the vehicle's parking brake
system is tested in an unburnished condition.
(d) Parking brake applications: 1 application and up to 2
reapplications, if necessary.
S7.12.2. Test conditions and procedures.
(a) IBT:
(1) Parking brake systems utilizing service brake friction materials
shall be tested with the IBT <= 100 [deg]C (212 [deg]F) and shall have
no additional burnishing or artificial heating prior to the start of the
parking brake test.
(2) Parking brake systems utilizing non-service brake friction
materials shall be tested with the friction materials at ambient
temperature at the start of the test. The friction materials shall have
no additional burnishing or artificial heating prior to or during the
parking brake test.
(b) Parking brake control force: Hand control <= 400 N (89.9 lbs);
foot control <= 500 N (112.4 lbs).
(c) Hand force measurement locations: The force required for
actuation of a hand-operated brake system is measured at the center of
the hand grip area or at a distance of 40 mm (1.57 in) from the end of
the actuation lever as illustrated in Figure 3.
(d) Parking brake applications: 1 application and up to 2
reapplications, if necessary.
[[Page 454]]
[GRAPHIC] [TIFF OMITTED] TC01AU91.073
(e) Test surface gradient: 20% grade.
(f) Drive the vehicle onto the grade with the longitudinal axis of
the vehicle in the direction of the slope of the grade.
(g) Stop the vehicle and hold it stationary by applying the service
brake control and place the transmission in neutral.
(h) With the service brake applied sufficiently to just keep the
vehicle from rolling, apply the parking brake as specified in S7.12.2(i)
or S7.12.2(j).
(i) For a vehicle equipped with mechanically-applied parking brakes,
make a single application of the parking brake control with a force not
exceeding the limits specified in S7.12.2(b). For a vehicle using an
electrically-activated parking brake, apply the parking brake by
activating the parking brake control.
(j) In the case of a parking brake system that does not allow
application of the specified force in a single application, a series of
applications may be made to achieve the specified force.
(k) Following the application of the parking brakes, release all
force on the service brake control and, if the vehicle remains
stationary, start the measurement of time.
(l) If the vehicle does not remain stationary, reapplication of a
force to the parking brake control at the level specified in S7.12.2(b)
as appropriate for the vehicle being tested (without release of the
ratcheting or other holding mechanism of the parking brake) is used up
to two times to attain a stationary position.
(m) Verify the operation of the parking brake application indicator.
(n) Following observation of the vehicle in a stationary condition
for the specified time in one direction, repeat
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the same test procedure with the vehicle orientation in the opposite
direction on the same grade.
S7.12.3. Performance requirement. The parking brake system shall
hold the vehicle stationary for 5 minutes in both a forward and reverse
direction on the grade.
S7.13. Heating Snubs.
S7.13.1. General information. The purpose of the snubs is to heat up
the brakes in preparation for the hot performance test which follows
immediately.
S7.13.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In gear.
S7.13.3. Test conditions and procedures. (a) IBT:
(1) Establish an IBT before the first brake application (snub) of
<=55 [deg]C (131 [deg]F), <=65 [deg]C (149 [deg]F).
(2) IBT before subsequent snubs are those occurring at the distance
intervals.
(b) Number of snubs: 15.
(c) Test speeds: The initial speed for each snub is 120 km/h (74.6
mph) or 80% of Vmax, whichever is slower. Each snub is terminated at
one-half the initial speed.
(d) Deceleration rate:
(1) Maintain a constant deceleration rate of 3.0 m/s2
(9.8 fps2).
(2) Attain the specified deceleration within one second and maintain
it for the remainder of the snub.
(e) Pedal force: Adjust as necessary to maintain the specified
constant deceleration rate.
(f) Time interval: Maintain an interval of 45 seconds between the
start of brake applications (snubs).
(g) Accelerate as rapidly as possible to the initial test speed
immediately after each snub.
(h) Immediately after the 15th snub, accelerate to 100 km/h (62.1
mph) and commence the hot performance test.
S7.14. Hot performance.
S7.14.1. General information. The hot performance test is conducted
immediately after completion of the 15th heating snub.
S7.14.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
S7.14.3. Test conditions and procedures. (a) IBT: Temperature
achieved at completion of heating snubs.
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force:
(1) The first stop is done with an average pedal force not greater
than the average pedal force recorded during the shortest GVWR cold
effectiveness stop.
(2) The second stop is done with a pedal force not greater than 500
N (112.4 lbs).
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds
allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 2 stops.
(f) Immediately after the 15th heating snub, accelerate to 100 km/h
(62.1 mph) and commence the first stop of the hot performance test.
(g) If the vehicle is incapable of attaining 100 km/h, it is tested
at the same speed used for the GVWR cold effectiveness test.
(h) Immediately after completion of the first hot performance stop,
accelerate as rapidly as possible to the specified test speed and
conduct the second hot performance stop.
(i) Immediately after completion of the second hot performance stop,
drive 1.5 km (0.93 mi) at 50 km/h (31.1 mph) before the first cooling
stop.
S7.14.4. Performance requirements. (a) For the first hot stop, the
stopping distance must be less than or equal to a calculated distance
which is based on 60 percent of the deceleration actually achieved on
the shortest GVWR cold effectiveness stop. The following equations shall
be used in calculating the performance requirement:
[GRAPHIC] [TIFF OMITTED] TR02FE95.015
where dc = the average deceleration actually achieved during
the shortest cold effectiveness stop at GVWR (m/s2),
Sc = actual stopping distance measured on the shortest cold
effectiveness stop at GVWR (m), and
V = cold effectiveness test speed (km/h).
[[Page 456]]
(b) In addition to the requirement in S7.14.4(a), the stopping
distance for at least one of the two hot stops must be S <= 89 m (292
ft) from a test speed of 100 km/h (62.1 mph) or, for reduced test speed,
S <= 0.10V + 0.0079V2. The results of the second stop may not
be used to meet the requirements of S7.14.4(a).
S7.15. Brake cooling stops.
S7.15.1. General information. The cooling stops are conducted
immediately after completion of the hot performance test.
S7.15.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In gear.
S7.15.3. Test conditions and procedures. (a) IBT: Temperature
achieved at completion of hot performance.
(b) Test speed: 50 km/h (31.1 mph).
(c) Pedal force: Adjust as necessary to maintain specified constant
deceleration rate.
(d) Deceleration rate: Maintain a constant deceleration rate of 3.0
m/s2 (9.8 fps2).
(e) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds
allowed at speeds greater than 15
km/h (9.3 mph).
(f) Number of runs: 4 stops.
(g) Immediately after the hot performance stops drive 1.5 km (0.93
mi) at 50 km/h (31.1 mph) before the first cooling stop.
(h) For the first through the third cooling stops:
(1) After each stop, immediately accelerate at the maximum rate to
50 km/h (31.1 mph).
(2) Maintain that speed until beginning the next stop at a distance
of 1.5 km (0.93 mi) from the beginning of the previous stop.
(i) For the fourth cooling stop:
(1) Immediately after the fourth stop, accelerate at the maximum
rate to 100 km/h (62.1 mph).
(2) Maintain that speed until beginning the recovery performance
stops at a distance of 1.5 km (0.93 mi) after the beginning of the
fourth cooling stop.
S7.16. Recovery performance.
S7.16.1. General information. The recovery performance test is
conducted immediately after completion of the brake cooling stops.
S7.16.2. Vehicle conditions. (a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
S7.16.3. Test conditions and procedures. (a) IBT: Temperature
achieved at completion of cooling stops.
(b) Test speed: 100 km/h (62.1 mph).
(c) Pedal force: The average pedal force shall not be greater than
the average pedal force recorded during the shortest GVWR cold
effectiveness stop.
(d) Wheel lockup: No lockup of any wheel for longer than 0.1 seconds
allowed at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 2 stops.
(f) Immediately after the fourth cooling stop, accelerate at the
maximum rate to 100 km/h (62.1 mph).
(g) Maintain that speed until beginning the first recovery
performance stop at a distance of 1.5 km (0.93 mi) after the beginning
of the fourth cooling stop.
(h) If the vehicle is incapable of attaining 100 km/h, it is tested
at the same speed used for the GVWR cold effectiveness test.
(i) Immediately after completion of the first recovery performance
stop accelerate as rapidly as possible to the specified test speed and
conduct the second recovery performance stop.
S7.16.4. Performance requirements.
The stopping distance, S, for at least one of the two stops must be
within the following limits:
[GRAPHIC] [TIFF OMITTED] TR02FE95.016
where dc and V are defined in S7.14.4(a).
S7.17. Final Inspection. Inspect:
(a) The service brake system for detachment or fracture of any
components, such as brake springs and brake shoes or disc pad facings.
(b) The friction surface of the brake, the master cylinder or brake
power unit reservoir cover, and seal and filler openings, for leakage of
brake fluid or lubricant.
(c) The master cylinder or brake power unit reservoir for compliance
with the volume and labeling requirements of S5.4.2 and S5.4.3. In
determining the fully applied worn condition, assume that the lining is
worn to (1) rivet or bolt heads on riveted or bolted linings or (2)
within 0.8 mm (1/32
[[Page 457]]
inch) of shoe or pad mounting surface on bonded linings or (3) the limit
recommended by the manufacturer, whichever is larger relative to the
total possible shoe or pad movement. Drums or rotors are assumed to be
at nominal design drum diameter or rotor thickness. Linings are assumed
adjusted for normal operating clearance in the released position.
(d) The brake system indicators, for compliance with operation in
various key positions, lens color, labeling, and location, in accordance
with S5.5.
[60 FR 6434, Feb. 2, 1995; as amended at 60 FR 37847, July 24, 1995; 60
FR 44548, Aug. 28, 1995; 62 FR 46917, Sept. 5, 1997; 62 FR 51070, Sept.
30, 1997; 65 FR 6332, Feb. 9, 2000]