§ 570.53 49 CFR Ch. V (10–1–12 Edition)

injuries attributable to failure or inad- pound force applied to the pedal equate performance of the motor vehi- and by no illumination of the brake cle systems covered by this part. system failure indicator lamp. The brake system shall withstand the ap- § 570.53 Applicability. plication of force to the pedal without This part does not in itself impose re- failure of any tube, hose or other part. quirements on any person. It is in- (1) Inspection procedure. With the en- tended to be implemented by States gine running in vehicles equipped with through the highway safety program power brake systems and the ignition standards issued under the Highway turned to ‘‘on’’ in other vehicles, apply Safety Act (23 U.S.C. 402) with respect a force of 125 pounds to the brake pedal to inspection of motor vehicles with and hold for 10 seconds. Note any addi- gross vehicle weight rating greater tional decrease in pedal height after than 10,000 pounds, except mobile the initial decrease, and whether the structure trailers. brake system failure indicator lamp il- luminates. [39 FR 28980, Aug. 13, 1974] (c) Brake pedal reserve. When the brake pedal is depressed with a force of § 570.54 Definitions. 50 pounds, the distance that the pedal Unless otherwise indicated, all terms has traveled from its free position shall used in this part that are defined in be not greater than 80 percent of the part 571 of this chapter, Motor Vehicle total distance from its free position to Safety Standards, are used as defined the floorboard or other object that re- in that part. stricts pedal travel. The brake pedal Air-over- subsystem reserve test is not required for vehicles means a subsystem of the with brake systems designed by the that uses compressed air to transmit a original vehicle, manufacturer to oper- force from the driver control to a hy- ate with greater than 80 percent pedal draulic brake system to actuate the travel. service . (1) Inspection procedure. Measure the Electric brake system means a system distance (i) from the free pedal position that uses electric current to actuate to the floor board or other object that the service brake. restricts brake pedal travel. Depress brake system means a system the brake pedal, and with the force ap- that uses a vacuum and atmospheric plied measure the distance (ii) from the pressure for transmitting a force from depressed pedal position to the floor the driver control to the service brake, board or other object that restricts but does not include a system that uses pedal travel. Determine the pedal trav- vacuum only to assist the driver in ap- el percentage as plying muscular force to hydraulic or [(A ¥ B) / A] × 100 mechanical components. The engine must be operating when § 570.55 Hydraulic brake system. power-assisted brakes are checked. The following requirements apply to (d) Brake hoses, master cylinder, tubes vehicles with hydraulic brake systems. and tube assemblies. Hydraulic brake (a) Brake system failure indicator. The hoses shall not be mounted so as to hydraulic brake system failure indi- contact the vehicle body or chassis. cator lamp, if part of a vehicle’s origi- Hoses shall not be cracked, chafed, or nal equipment, shall be operable. flattened. Brake tubes shall not be flat- (1) Inspection procedure. Apply the tened or restricted. Brake hoses and and turn the ignition to tubes shall be attached or supported to start to verify that the brake system prevent damage by vibration or abra- failure indicator lamp is operable, or sion. Master cylinder shall not show verify by other means recommended by signs of leakage. Hose or tube protec- the vehicle manufacturer. tive rings or devices shall not be con- (b) Brake system integrity. The hydrau- sidered part of the hose or tubing. lic brake system shall demonstrate in- (1) Inspection procedure. Examine vis- tegrity as indicated by no perceptible ually brake master cylinder, hoses and decrease in pedal height under a 125- tubes, including front brake hoses,

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through all wheel positions from full with brake chamber rods, observe the left turn to full right turn for condi- chamber rod movement. Run the en- tions indicated. gine to re-establish maximum vacuum, [39 FR 26027, July 16, 1974, as amended at 40 then shut off the engine and apply the FR 5160, Feb. 4, 1975] brakes with a 50-pound force on the brake pedal. Note the brake applica- § 570.56 Vacuum brake assist unit and tion and check for low-vacuum indi- vacuum brake system. cator activation. The following requirements apply to (ii) For a combination vehicle vehicles with vacuum brake assist equipped with breakaway protection units and vacuum brake systems. and no reservoir on the towing vehicle (a) Vacuum brake assist unit integrity. supply line, close the supply line shut- The vacuum brake assist unit shall off valve and disconnect the supply demonstrate integrity as indicated by line. Apply a 50-pound force to the a decrease in pedal height when the en- brake pedal on the towing vehicle and gine is started and a constant 50-pound release. Trailer brakes should remain force is maintained on the pedal. in the applied position. (1) Inspection procedure. Stop the en- (d) Vacuum system hoses, tubes and gine and apply service brake several connections. Vacuum hoses, tubes and times to destroy vacuum in system. connections shall be in place and prop- Depress the brake pedal with 50 pounds erly supported. Vacuum hoses shall not of force and while maintaining that be collapsed, cracked or abraded. force, start the engine. If the brake (1) Inspection procedure. With the en- pedal does not move slightly under gine running, examine hoses and tubes force when the engine starts, there is a for the conditions indicated and note malfunction in the power assist unit. broken or missing clamps. (b) Low-vacuum indicator. If the vehi- cle has a low-vacuum indicator, the in- § 570.57 Air brake system and air-over- dicator activation level shall not be hydraulic brake subsystem. less than 8 inches of mercury. The following requirements apply to (1) Inspection procedure. Run the en- vehicles with air brake and air-over- gine to evacuate the system fully. Shut hydraulic brake systems. Trailer(s) off the engine and slowly reduce the must be coupled to a truck or truck- vacuum in the system by moderate tractor for the purpose of this inspec- brake applications until the vehicle tion, except as noted. vacuum gauge reads 8 inches of mer- (a) Air brake system integrity. The air cury. Observe the functioning of the brake system shall demonstrate integ- low-vacuum indicator. rity by meeting the following require- (c) Vacuum brake system integrity. (1) ments: The vacuum brake system shall dem- (1) With the vehicle in a stationary onstrate integrity by meeting the fol- position, compressed air reserve shall lowing requirements: be sufficient to permit one full service (i) The vacuum brake system shall brake application, after the engine is provide vacuum reserve to permit one stopped and with the system fully service brake application with a brake charged, without lowering reservoir pedal force of 50 pounds after the en- pressure more than 20 percent below gine is turned off without actuating the initial reading. the low vacuum indicator. (2) The air brake system compressor (ii) Trailer vacuum brakes shall oper- shall increase the air pressure in the ate in conjunction with the truck or reservoir(s) from the level developed truck tractor brake pedal. after the test prescribed in § 570.57(a)(1) (2) Inspection procedure. (i) Check the to the initial pressure noted before the trailer vacuum system by coupling full brake application, with the engine trailer(s) to truck or truck tractor and running at the manufacturer’s max- opening trailer shutoff valves. Start imum recommended number of revolu- the engine and after allowing approxi- tions per minute with the compressor mately 1 minute to build up the vacu- governor in the cut-off position, in not um, apply and release the brake pedal. more than 30 seconds for vehicles man- In the case of trailer brakes equipped ufactured prior to March 1, 1975. For

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