Brake Components

PURPOSE: This rule describes the procedures and standards for the inspection of brake components. The inspection of brakes is a requirement of section 307.365, RSMo. (1) Hydraulic System. (A) Pedal Reserve. With the vehicle stopped, apply moderate foot force on the brake pedal for at least one (1) minute and observe if the pedal moves slowly toward toe board. 1. Reject vehicle if: A. Brake pedal moves slowly toward the toe board, indicating fluid leakage, while pedal pressure is maintained for one (1) minute; B. Less than one-fifth (1/5) of the total available pedal travel remains; C. Less than two-fifths (2/5) of total available pedal travel remains on a school bus; or D. The brake warning device or light comes on when the brake pedal is depressed. Do not inspect the anti-lock braking system warning device or light. (B) Power Reserve. Determine if system is operating by first stopping engine, then depress brake pedal several times to destroy all vacuum in system. Depress pedal with a moderate HIGHWAY PATROL foot force. While maintaining this force on the pedal, start engine; and observe if pedal falls slightly when engine starts. Hydroboost system must have accumulator pressure for two (2) complete brake applications and should have return pressure against foot. If vehicle is equipped with electrohydraulic booster brake system, stop engine, turn ignition to the “on” position, depress brake pedal, and observe if electric pump, buzzer, and pump indicator lights operate. Inspect school buses manufactured after March 1, 1987, for audible or visible brake warning signals, or both. 1. Reject vehicle if: A. Service brake pedal does not fall slightly as engine is started while pressure is maintained on pedal; B. There is audible leakage in the vacuum system; C. Hydroboost brake system does not have two (2) brake applications available; D. Electric pump, buzzer, and pump indicator lights fail to function on vehicles equipped with electrohydraulic booster brake system; or E. School bus manufactured after March 1, 1987, is not equipped with proper audible or visible brake warning signals, or both, or signals fail to function. (C) Master Cylinder. Inspect master cylinder for proper fluid, fluid level, fluid leakage, and play in push rod. Power master-type systems should have the brake pedal depressed ten to forty (10–40) times or until the pedal is firm, with the ignition off, before inspecting fluid level. Master cylinder reservoirs with distinctly marked minimum levels should be inspected with the cap on. Observe the fluid level to ensure it complies with the manufacturer’s suggested minimum level. The cap will then be removed to inspect the gasket for fluid contamination, swelling, cracking, misshape, or tears. 1. Reject vehicle if: A. Master cylinder contains fluid other than brake fluid, if master cylinder leaks, if fluid level is more than three-fourths inch (3/4") below top of reservoir; B. Vehicle with disc brakes and dual hydraulic systems show the brake fluid level measuring more than one-half inch (1/2") below the top of the reservoir on master cylinders that have no manufacturer’s minimum markings; C. Master cylinder brake fluid level is below the manufacturer’s minimum fluid level as marked on the reservoir; D. There is no play in the push rod with brake pedal not depressed; or E. Master cylinder gasket is torn or misshaped. (2) Drums, Discs, and Internal Brake Components. At least one (1) front or one (1) rear wheel and drum must be removed on each passenger vehicle, one-half (1/2) ton and three-quarter (3/4) ton pickup trucks, or similar type vehicles not equipped with dual rear wheels. Only the wheel must be removed on vehicles equipped with disc brakes. Identification marks shall be made on the wheel and lug before removal, so the wheel can be remounted in the same position to insure wheel balance. On drum brake systems, a new cotter pin must always be used when remounting a wheel and drum. The removal of a wheel and/or drum is not required if the brake performance test has been administered using an approved computerized brake testing machine. When an approved computerized brake testing machine is used, and no wheel is removed, the inspector shall mark through the space on the MVI-2 form provided for “Brake Inspected” with the letters “CBTM.” When removal of a wheel is required, a wheel appearing to leak brake fluid or grease, shall be the wheel removed to inspect for contamination. Wheels on four- (4-) wheel drive vehicles equipped exclusively with drum-type brakes are not required to be removed. (A) Inspect drums, discs, calipers, linings, pads, wheel cylinders, hoses, lines, and other internal brake components. 1. Reject vehicle if— A. There are substantial cracks on the friction surface extending to open edge of drum or to the edge of a disc; B. A brake drum or disc has external cracks; C. Friction surface of disc brake pads, rotor, brake linings, or brake drum is contaminated with oil, grease, or brake fluid; D. A brake lining is worn into the friction surface of the brake drum where the brake drum cannot be removed after loosening the adjusting screw (backing off of the self-adjusting mechanism); E. Thinnest point of bonded lining is less than two thirty-seconds inch (2/32"); F. Rivets are loose or missing or if lining or pad is not firmly attached to shoe; G. Riveted lining is worn to less than two thirty-seconds inch (2/32") above any rivet head at thinnest point; H. Wire is visible on the friction surface of wire-backed linings; I. Lining is broken or cracked, does not include heat cracks; J. A primary or secondary shoe and lining is improperly installed; K. Bonded pads are worn at any one (1) point to less than two thirty-seconds inch (2/32"); L. Riveted pads are worn at any one (1) point to less than six thirty-seconds inch (6/32"). If unable to determine if pads are riveted or bonded, pads will be considered to be bonded pads; M. A wheel cylinder or caliper leaks a sufficient amount of hydraulic brake fluid to cause droplets. Do not mistake assembly fluid for hydraulic fluid; N. Hoses or tubing leak or are cracked, chafed, flattened, restricted, bubbled, improperly installed, or insecurely fastened; O. Mechanical parts are missing, broken, or badly worn; P. There is excessive friction in brake pedal, linkage, or other components; Q. Pedal levers are improperly positioned or misaligned; or R. Brake components are misaligned, binding, obstructed, or will not function properly. AUTHORITY: section 307.360, RSMo 2016.* Original rule filed Nov. 4, 1968, effective Nov. 14, 1968. Amended: Filed Dec. 5, 1969, effective Dec. 15, 1969. Amended: Filed March 9, 1970, effective March 19, 1970. Amended: Filed Nov. 9, 1971, effective Nov. 19, 1971. Amended: Filed May 21, 1974, effective May 31, 1974. Amended: Filed Dec. 1, 1975, effective Dec. 11, 1975. Amended: Filed Sept. 1, 1977, effective Dec. 11, 1977. Amended: Filed Jan. 16, 1978, effective April 13, 1978. Amended: Filed March 3, 1980, effective June 12, 1980. Amended: Filed Jan. 12, 1982, effective April 11, 1982. Amended: Filed Aug. 26, 1985, effective Nov. 28, 1985. Amended: Filed Aug. 14, 1987, effective Nov. 12, 1987. Amended: Filed April 2, 1992, effective Sept. 6, 1992. Amended: Filed June 2, 1993, effective Nov. 8, 1993. Amended: Filed Oct. 3, 1994, effective April 30, 1995. Emergency rescission and rule filed May 15, 1997, effective June 16, 1997, expired Nov. 30, 1997. Rescinded and readopted: Filed May 15, 1997, effective Nov. 30, 1997. Amended: Filed March 15, 1999, effective Sept. 30, 1999. Emergency amendment filed Feb. 1, 2000, effective July 1, 2000, expired Dec. 27, 2000. Amended: Filed Feb. 1, 2000, effective July 30, 2000. Amended: Filed Sept. 15, 2003, effective March 30, 2004. Amended: Filed Oct. 3, 2005, effective March 30, 2006. Amended: Filed Oct. 30, 2020, effective June 30, 2021. *Original authority: 307.360, RSMo 1967, amended 1971, 1973, 1979, 1999.