Nat’l Highway Traffic Safety Admin., DOT § 570.56

§ 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 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, pound force applied to the brake pedal through all wheel positions from full and by no illumination of the brake left turn to full right turn for condi- system failure indicator lamp. The tions indicated. brake system shall withstand the ap- plication of force to the pedal without [39 FR 26027, July 16, 1974, as amended at 40 failure of any tube, hose or other part. FR 5160, Feb. 4, 1975] (1) Inspection procedure. With the en- gine running in vehicles equipped with § 570.56 Vacuum brake assist unit and power brake systems and the ignition vacuum brake system. turned to ‘‘on’’ in other vehicles, apply The following requirements apply to a force of 125 pounds to the brake pedal vehicles with vacuum brake assist and hold for 10 seconds. Note any addi- units and vacuum brake systems. tional decrease in pedal height after (a) Vacuum brake assist unit integrity. the initial decrease, and whether the The vacuum brake assist unit shall brake system failure indicator lamp il- demonstrate integrity as indicated by luminates. a decrease in pedal height when the en- (c) Brake pedal reserve. When the gine is started and a constant 50-pound brake pedal is depressed with a force of force is maintained on the pedal.

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