[Code of Federal Regulations]

[Title 49, Volume 5]

[Revised as of October 1, 2005]

From the U.S. Government Printing Office via GPO Access

[CITE: 49CFR393.47]



[Page 400]

 

                        TITLE 49--TRANSPORTATION

 

                      DEPARTMENT OF TRANSPORTATION

 

PART 393_PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION--Table of 

Contents

 

                            Subpart C_Brakes

 

Sec. 393.47  Brake actuators, slack adjusters, linings/pads and 

drums/rotors.



    (a) General requirements. Brake components must be constructed, 

installed and maintained to prevent excessive fading and grabbing. The 

means of attachment and physical characteristics must provide for safe 

and reliable stopping of the commercial motor vehicle.

    (b) Brake chambers. The service brake chambers and spring brake 

chambers on each end of an axle must be the same size.

    (c) Slack adjusters. The effective length of the slack adjuster on 

each end of an axle must be the same.

    (d) Linings and pads. The thickness of the brake linings or pads 

shall meet the applicable requirements of this paragraph--

    (1) Steering axle brakes. The brake lining/pad thickness on the 

steering axle of a truck, truck-tractor or bus shall not be less than 

4.8 mm (\3/16\ inch) at the shoe center for a shoe with a continuous 

strip of lining; less than 6.4 mm (\1/4\ inch) at the shoe center for a 

shoe with two pads; or worn to the wear indicator if the lining is so 

marked, for air drum brakes. The steering axle brake lining/pad 

thickness shall not be less than 3.2 mm (\1/8\ inch) for air disc 

brakes, or 1.6 mm (\1/16\ inch) or less for hydraulic disc, drum and 

electric brakes.

    (2) Non-steering axle brakes. An air braked commercial motor vehicle 

shall not be operated with brake lining/pad thickness less than 6.4 mm 

(\1/4\ inch) or to the wear indicator if the lining is so marked 

(measured at the shoe center for drum brakes); or less than 3.2 mm (\1/

8\ inch) for disc brakes. Hydraulic or electric braked commercial motor 

vehicles shall not be operated with a lining/pad thickness less than 1.6 

mm (\1/16\ inch) (measured at the shoe center) for disc or drum brakes.

    (e) Clamp and Roto-Chamber Brake Actuator Readjustment limits. The 

pushrod travel for clamp and roto-chamber type actuators must be less 

than 80 percent of the rated strokes listed in SAE J1817--Long Stroke 

Air Brake Actuator Marking, July 2001 (See Sec. 393.7 (b) for 

information on incorporation by reference and availability of this 

document), or 80 percent of the rated stroke marked on the brake chamber 

by the chamber manufacturer, or the readjustment limit marked on the 

brake chamber by the chamber manufacturer. The pushrod travel for Type 

16 and 20 long stroke clamp type brake actuators must be less than 51 mm 

(2 inches) or 80 percent of the rated stroke marked on the brake chamber 

by the chamber manufacturer, or the readjustment limit marked on the 

brake chamber by the chamber manufacturer.

    (f) Wedge Brake Adjustment. The movement of the scribe mark on the 

lining shall not exceed 1.6 mm (\1/16\ inch).

    (g) Drums and rotors. The thickness of the drums or rotors shall not 

be less than the limits established by the brake drum or rotor 

manufacturer.



[70 FR 48051, Aug. 15, 2005]