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:
Backup system means a portion of a service brake system, such as a pump, that automatically supplies energy, in the event of a primary brake power source failure.
Brake power assist unit means a device installed in a hydraulic brake system that reduces the operator effort required to actuate the system, and that if inoperative does not prevent the operator 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 the operator action consisting only of modulating the energy application level.
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.
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.
Full brake application means a brake application in which the force on the brake pedal reaches 150 pounds within 0.3 seconds from the point of application of force to the brake control.
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.
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 wheels.
Initial brake temperature means the average temperature of the service brakes on the hottest axle of the vehicle 0.2 mi before any brake application.
Lightly loaded vehicle weight means:
Maximum drive-through speed means the highest possible constant speed at which the vehicle can be driven through 200 feet of a 500-foot radius curve arc without leaving the 12-foot lane.
Parking mechanism means a component or subsystem of the drive train that locks the drive train when the transmission control is placed in a parking or other gear position and the ignition key is removed.
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 batteries or dissipating electrical energy.
Skid number means the frictional resistance of a pavement measured in accordance with ASTM E274-70 (incorporated by reference, see § 571.5 ) at 40 mph, omitting water delivery as specified in paragraphs 7.1 and 7.2 of that method.
Snub means the braking deceleration of a vehicle from a higher reference speed to a lower reference speed that is greater than zero.
Spike stop means a stop resulting from the application of 200 lbs of force on the service brake control in 0.08 s.
Split service brake system means a brake system consisting of two or more 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.
Tandem axle means a group of two or more axles placed in close arrangement one behind the other with the center lines of adjacent axles not more than 72 inches apart.
Variable proportioning brake system means a system that automatically adjusts the braking force at the axles to compensate for vehicle static axle loading and/or dynamic weight transfer between axles during deceleration.
Wheel lockup means 100 percent wheel slip.
If the speed attainable in 2 miles is not less than 99 mph, a passenger car shall, in addition, be capable of stopping from the applicable speed indicated below, within the corresponding distance specified in column I of table II.
Speed attainable in 2 miles (mph) | Required to stop from (mph) |
Not less than 99 but less than 104 | 95 |
104 or more | 100 |
For an EV, the speed attainable in 2 miles is determined with the propulsion batteries at a state of charge of not less than 95 percent at the beginning of the run.
whichever is lower (but in no case lower than 5 pounds).
whichever is lower (but in no case lower than 5 pounds).
whichever is lower (but in no case lower than 5 pounds).
whichever is lower (but in no case lower than 5 pounds).
Determine whether the brake system indicator lamp is activated when the electrical power source to the antilock or variable proportioning unit is disconnected.
At the completion of the stops specified above, deplete the system of any residual brake power reserve capability. Make one stop from 60 mph at an average deceleration of not lower than 7 fpsps for passenger cars (equivalent stopping distance 554 feet), or 6 fpsps for vehicles other than passenger cars (equivalent stopping distance 646 feet) and determine whether the control force exceeds 150 pounds.
Note: The vehicle used for this test need not be the same vehicle that has been used for the braking tests.
FIGURE 1-TYPICAL PLUG THERMOCOUPLE INSTALLATIONS
Note: The second thermocouple shall be installed at .080 inch depth within 1 inch circumferentially of the thermocouple installed at .040 inch depth.
Table I-Brake Test Procedure Sequence and Requirements
Sequence | Test load | Test procedure | Requirements | |
Light | GVWR | |||
1. Instrumentation check | S7.2 | |||
2. First (preburnish) effectiveness test | X | S7.3 | S5.1.1.1 | |
3. Burnish procedure | X | S7.4 | ||
4. Second effectiveness test | X | S7.5(b) | S5.1.1.2 | |
5. First reburnish | X | S7.6 | ||
6. Parking brake | X | X | S7.7 | S5.2 |
7. Stability and control during braking (braking-in-a-curve test) | X | S7.5(a) | S5.1.7 | |
8. Third effectiveness (lightly loaded vehicle) | X | S7.8 | S5.1.1.3 | |
9. Partial failure | X | X | S7.9 | S5.1.2 |
10. Inoperative brake power and power assist units | X | S7.10 | S5.1.3 | |
11. First fade and recovery | X | S7.11 | S5.1.4 | |
12. Second reburnish | X | S7.12 | ||
13. Second fade and recovery | X | S7.13 | S5.1.4 | |
14. Third reburnish | X | S7.14 | ||
15. Fourth effectiveness | X | S7.15 | S5.1.1.4 | |
16. Water recovery | X | S7.16 | S5.1.5 | |
17. Spike stops | X | S7.17 | S5.1.6 | |
18. Final inspection | S7.18 | S5.6 | ||
19. Moving barrier test | X | S7.19 | S5.2.2.3 |
Table III-Inoperative Brake Power Assist and Brake Power Units
Stop No. | Average deceleration, FPSPS | Equivalent stopping distance, feet | ||||||
Column 1-brake power assist | Column 2-brake power unit | Column 3-brake power assist | Column 4-brake power unit | |||||
(a) | (b) and (c) | (a) | (b) and (c) | (a) | (b) and (c) | (a) | (b) and (c) | |
1 | 16.0 | 14.0 | 16.0 | 13.0 | 242 | 277 | 242 | 298 |
2 | 12.0 | 12.0 | 13.0 | 11.0 | 323 | 323 | 298 | 352 |
3 | 10.0 | 10.0 | 12.0 | 10.0 | 388 | 388 | 323 | 388 |
4 | 9.0 | 8.5 | 11.0 | 9.5 | 431 | 456 | 352 | 409 |
5 | 8.0 | 7.5 | 10.0 | 9.0 | 484 | 517 | 388 | 431 |
6 | 7.5 | 6.7 | 9.5 | 8.5 | 517 | 580 | 409 | 456 |
7 | 1 7.0 | 1 6.0 | 9.0 | 8.0 | 554 | 646 | 431 | 484 |
8 | NA | NA | 8.5 | 7.5 | NA | NA | 456 | 517 |
9 | NA | NA | 8.0 | 7.0 | NA | NA | 484 | 554 |
10 | NA | NA | 7.5 | 6.5 | NA | NA | 517 | 596 |
11 | NA | NA | 1 7.0 | 1 6.0 | NA | NA | 554 | 646 |
1 Depleted. (a) Passenger cars; (b) vehicles other than passenger cars with GVWR of 10,000 lbs or less; (c) vehicles with GVWR greater than 10,000 lbs; NA = Not applicable.
49 C.F.R. §571.105
For FEDERAL REGISTER citations affecting § 571.105, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed volume and at www.govinfo.gov.