Procedures: | Reject Vehicle If: |
(a) Service Brake Test: Method (1)-On Road: At a speed of 20 mph apply service brakes firmly. Observe whether the vehicle comes to a smooth stop. | (a) Required stopping distance is greater than that contained in brake performance chart. |
(b) Service Brake Test: Method (2)- On Road: Mount an approved decelerometer at centerline of vehicle. Level the decelerometer. At the speed of 20 mph, apply service brake firmly. Observe decelerometer reading. Determine whether vehicle pulls to the right or left. | (b) The vehicle develops less deceleration than that contained in the brake performance chart. (c) Vehicle pulls severely to the right or left upon brake application. |
Procedures: | Reject Vehicle If: |
(a) Method (3)-Platform Tester: Drive vehicle onto drive-on-and-stop platform tester. Apply brakes firmly at a speed from 4 to 8 mph without wheel lockup. All braking action shall take place on the platform. | (a) Required stopping distance is greater than that contained in brake performance chart. |
(b) This equipment may be used to inspect the relative effectiveness of each wheel. There shall be braking action on all wheels and the action on any one wheel shall be 75 percent or more of the action of the other wheel on the same axle. | (b) Any wheel fails to indicate braking action. If the reading on any one wheel is less than 75 percent of the reading on the other wheel on the same axle. |
Procedures: | Reject Vehicle If: |
(a) Method (4)-Roller-Type Brake Dynamometer (Force Measuring Type): (i) Adjust tire to proper inflation. (ii) Position vehicle on dynamometer rolls and begin test. (iii) Follow equipment manufacturer's recommended testing procedures. | (a) Readings are less than requirements on brake performance chart. (b) Any wheel fails to indicate braking action. If the reading on any one wheel is less than 75 percent of the reading on other wheel on the same axle. |
Procedures: | Reject Vehicle If: |
(a) Hydraulic System Leakage Test: While the vehicle is stopped, depress brake pedal under moderate foot force. The pedal height shall remain constant for 1 minute. | (a) Brake pedal height cannot be maintained for 1 minute. (b) (i) Less than 1/3 of the total available pedal travel remains. |
(b) Pedal Reserve Test: (i) While the vehicle is stopped, depress brake pedal under moderate foot force. (ii) On vacuum assisted hydraulic systems with master cylinder booster, pedal travel has no significance. Do not inspect this item. | (c) Air power assist push rod moves slowly toward master cylinder while air pressure is maintained for 1 minute. |
(c) Hydraulic system with air power assist test for leakage. Apply 2-3 psi air pressure and maintain for 1 minute. |
Procedures: | Reject Vehicle If: |
(a) Hydraulic System-Visually inspect condition of hydraulic system. (i) Inspect wheel cylinders for leakage and operation. Do not remove dust covers. | (a) (i) Wheel cylinders leak. |
(ii) Inspect hydraulic hoses and brake lines for leaks, cracks, chafing, flattened or restricted section, and improper support. | (ii) Hoses, brake lines are cracked, chafed, flattened, restricted, are rusted and pitting is visible, are insecurely fastened, or lines have been repaired or replaced with copper tubing or other material not designed for hydraulic brake lines. Hoses or brake lines are mounted to contact wheels or body during steering or suspension movement. |
(iii) Inspect master cylinder for leakage and fluid level (be sure no dirt gets into reservoir when cover is removed and that the gasket is serviceable). | (iii) Master cylinder leaks. (iv) The fluid level in any section is less than 1/2 full. (v) The gasket does not properly seal master cylinder. (vi) Wheel cylinders fail to operate. |
(b) Dual Hydraulic Circuits-In addition to the above, if vehicle is equipped with a brake warning light: (i) Test for operation of light; (ii) With ignition switch on, apply moderate foot force, and observe light; (iii) Inspect both sections of reservoir. | (b) (i) Light is burned out. (ii) Light comes on when brake pedal is depressed. (iii) The fluid level in any section is less than 1/2 full. |
(c)(i) Brakes fail to function when applied. (ii) Brakes do not remain applied until released. |
Procedures: | Reject Vehicle If: |
(a) Brake Drums: (i) Inspect the condition of the drum friction surface for any crack extending to the open edge of the drum (short hairline cracks should not be considered). (ii) Inspect any crack on the outside of the drum. (iii) Inspect for mechanical damage. (iv) Inspect for contaminated friction surface. (v) Measure inside diameter of drum. | (a) (i) There is a crack on the friction surface extending to the open edge of the drum. (ii) There is any external crack. (iii) There is evidence of excessive mechanical damage other than wear. (iv) Friction surface is contaminated with oil, grease, or brake fluid. (v) Inside drum diameter is greater than manufacturer's recommended limit, or the diameter stamped on the drum. |
(b) Brake Discs (if equipped): (i) Inspect for any crack extending to edge of disc. (ii) Inspect for mechanical damage. (iii) Inspect for contaminated friction surface. | (b) (i) There is any crack extending to the edge of the disc. (ii) If a crack extends into the weld or more than one-half the outside diameter of a BF Goodrich steel disc. (iii) There is evidence of excessive mechanical damage other than wear. (iv) Friction surface is contaminated with oil, grease, or brake fluid. (v) Thickness of disc is less than manufacturer's recommended limit or the thickness stamped on the disc. |
Procedures: | Reject Vehicle If: |
(1) Condition of Linings and Pads: (a) Bonded Linings: Measure the lining thickness at the thinnest point. | (1) (a) Thinnest point of remaining bonded lining is less than 2/32 inch. |
(b) Riveted Linings: (i) Inspect for loose or missing rivets. (ii) Measure lining thickness above rivet head at thinnest point. | (b) Riveted Linings: (i) Any rivet is loose or missing. (ii) Remaining lining is less than 2/32 inch above any rivet head. |
(c) Wire-Backed Linings: Inspect for wire showing in the friction surface. | (c) Wire backing is visible in the friction surface. |
(d) Bolted Linings (for buses and heavy vehicles): (i) Inspect for loose or missing bolts. (ii) Measure lining thickness at center of shoe. | (d) Bolted Linings (for buses and heavy vehicles): (i) Any fastening parts are loose or missing. (ii) Remaining lining is less than 5/16 inch at center of shoe. |
(e) All linings: Inspect for broken or cracked linings, and parts of linings not firmly attached to shoe. Also inspect for contamination and excessively uneven lining wear. | (e)(i) Lining is broken, cracked, or not firmly and completely attached to shoe. (ii) Friction surface is contaminated with oil or grease. (iii) Lining wear is extremely uneven. |
(f) Pads (Disc Brakes): Inspect thickness of friction pads. Many newer disc brake friction pads for vehicles in excess of 10,000 pounds GVWR are manufactured with a heat dissipator which is, in most instances, approximately 7/32 of an inch thick between the friction pad and the metal pad plate. These dissipators, if allowed to contact the rotor, will cause damage to the rotor. Therefore, when measuring disc brake friction pad thickness, it must first be determined if the braking system being inspected is equipped with these heat dissipators. If heat dissipators are present, the brake friction pad thickness shall be measured so that no portion of the heat dissipator is included in the measurement. If no heat dissipators are present, the brake friction pad thickness will be measured in the normal manner to the metal pad plate or rivets. | (f)(i) Any pad is less than 2/32 inch. (ii) Any pad on BF Goodrich Air Actuated Disc Brakes has 1/8 inch or less lining remaining. |
Procedures: | Reject Vehicle If: |
(1) Condition of Mechanical Components: | (1) |
(a) Inspect for worn pins and missing or defective cotter pins. | (a) Mechanical parts are missing, broken, or badly worn. |
(b) Inspect for broken, missing or worn springs, cables, clevises, couplings, rods, and anchor pins. | (b) Grease retainers are leaking (dampness is not cause for rejection). |
(c) Inspect for frozen, rusted, or inoperative connections, missing spring clips, and defective grease retainers. | (c) There is excessive friction in pedal and linkage or in brake components. |
(d) Inspect pedal shaft and bearings for high friction, wear, and misalignment. | (d) Pedal levers are improperly positioned or misaligned. |
(e) Inspect for restriction of shoe movement at backing plate and for binding between brake shoes and anchor pins. | (e) Conversion of a self-adjusting mechanism that is not completely converted. |
Procedures: | Reject Vehicle If: |
(1) Condition of Vacuum Booster System: Visually inspect system for collapsed, broken, badly chafed, and improperly supported hoses and tubing, and loose or broken hose. clamps. | (1) (a) Hoses and tubing are leaking, collapsed, broken, badly chafed, improperly supported, or loose because of broken clamps. (b) Hose or tubing is in good condition but exposed to danger from excessive heat, flying debris or rubbing. |
(2) Operation of Vacuum Booster System: (a) Determine whether system is operating by first stopping engine, then depress brake pedal several times to deplete all vacuum in system. (b) Then depress pedal with a light force. While maintaining this force on the pedal, start engine, and observe whether pedal moves slightly when engine starts. | (2) Service brake pedal does not move slightly when engine is started while pressure is maintained on pedal. |
(3) Vacuum Reserve and Low Vacuum Indicators: (a) Build full vacuum, then shut off engine and make as many full brake applications as possible. (b) On vehicles with low vacuum indicator, build full vacuum, then shut off engine and reduce vacuum by making a series of moderate brake applications. A visible or audible signal should function when vacuum reaches 8 inches Hg on gauge. | (3) (a) Vacuum reserve is insufficient to make one full application after engine shutoff. (b) Indicator fails to function when the system is reduced to 8 inches Hg vacuum. |
Procedures: | Reject Vehicle If: |
(1) With air system fully charged, open all drain cocks in the system until gauge indicates zero pressure. | (1) Time required to build pressure from 50-90 psi at fast idle exceeds: (a) Single unit vehicle and school vehicle-3 minutes; or (b) Combination vehicle-5 minutes. |
(2) Then close drain cocks and run engine at fast idle; record time to raise air pressure from 50-90 psi on gauge. | (2) Low pressure warning fails to function when pressure is lowered to 60 psi. |
(3) Observe gauge pressure at which signal on low pressure indicator goes out or off. | (3) Governor cut-out pressure is higher than 135 psi. |
(4) Continue running engine and observe gauge pressure when governor cuts out. | (4) Governor cut-in pressure is lower than 80 psi. |
(5) With engine idling, make a series of brake applications and observe pressure when governor cuts in. |
Procedures: | Reject Vehicle If: | |
(1) Air Leakage in System: Inspection for air leakage shall be made in two ways: | (1) Leakage exceeds the following limits: | |
Brakes Fully Applied | Brakes Released | |
(a) With a fully charged system, stop engine and record the pressure drop in psi per minute with brakes fully applied. (b) With a fully charged system, stop engine and record the pressure drop in psi per minute with brakes released. | Single unit school vehicles-3 psi per minute. Combination vehicles-4 psi per minute. | Single unit vehicles and school vehicles-2 psi per minute. Combination vehicles-3 psi per minute. |
(2) Compressed Air Reserve: (a) Make a series of brake applications until low pressure warning signal operates. Stop engine and make one full brake application. (b) With a fully charged system, stop engine and make one full brake application. Measure drop in reservoir pressure. | (2) (a) Air reserve is not sufficient to permit one full brake application after engine is stopped. (b) Reservoir pressure is lowered more than 20 percent of the first reading. | |
(3) General Condition: (a) Inspect all air hoses, tubes, and connections. Check attachments of all connecting lines and look for proper supporting parts. Be sure lines are free from contact with frame, axles, exhaust system, or other lines. (b) Inspect for leaks that may be heard from valves, diaphragms, piston cups, and connections. (c) Inspect air pressure relief valve, tension and condition of compressor drive belts. Check air intake cleaner for being clogged or restricted. | (3) (a) There are leaks, breaks, crimps, or cracks in the air hoses, tubes, or connections. (b) Lines are being chafed by moving parts, or are touching the exhaust system. (c) Leaks in valves, diaphragms, piston cups, or connections can be heard. (d) Air pressure relief valve does not operate. (e) Compressor drive belts are badly worn, frayed, or loose. (f) Air intake cleaner is clogged or restricted enough to prevent proper air intake. |
Procedures: | Reject Vehicle If: |
(1) Air Brake Parking and Emergency Systems: (a) With air pressure in the braking system at operational level, set parking brake control and observe functioning of parking and emergency braking at wheels. | (1) (a) System fails to function properly. (b) Vehicle can be moved with zero air pressure in system. |
(b) Drain air from the system and observe whether parking and emergency brakes remain in an applied position (with no air pressure in the system, vehicle should remain "braked"). |
Procedures: | Reject Vehicle If: |
(1) Actuator Reserve Test: (a) On air or vacuum mechanical brakes, measure the stroke of the air or vacuum chambers from fully released to fully applied position. (b) On air-over-hydraulic brake systems, measure air chamber travel from fully released to fully applied position (some systems include a rod gauge for visual checking). | (1) (a) The push rod travel on S-Cam Brakes exceeds the maximum stroke listed in S-Cam Brakes-Push Rod Travel Limits Chart. (i) Push rod travel on BF Goodrich Air Actuated Disc Brakes exceeds manufacturer's specification. |
(2) Push Rod/Slack Adjuster Angle: Measure push rod/slack adjuster angle with brakes applied. | (2) Push rod/slack adjuster angle is less than 90 degrees with brakes applied. |
(3) Wedge Brakes Shoe Movement: Measure total shoe movement from released to applied positions. | (3) Brake shoe movement on wedge brakes exceeds 1/16 inch. |
Figure 16-BRAKE CHAMBER PUSH ROD TRAVEL(TYPICAL).
Procedures: | Reject Vehicle If: |
(1) Emergency System-Function: (a) Fully apply the emergency operating control, or release air pressure from the spring brake actuator using the manual control valve. Then: (i) Observe locking and holding feature of the actuating mechanism. (ii) Observe operating mechanism for "bottoming" before brakes are fully applied. (iii) Observe if spring brakes apply when control valve is manually operated. (iv) Inspect for worn, missing, or defective cotter pins, springs, rods, yokes, couplings, or anchor pins and cables. (v) Observe if mechanism releases brakes when release control is operated. | (1) (a) (i) Operating mechanism fails to hold brakes in applied position without manual effort. (ii) Operating mechanism "bottoms" before brakes are fully applied. (iii) Spring brakes fail to apply when control valve is operated. (iv) Mechanical parts are missing, broken, or badly worn, or pull cables are badly worn, stretched, frayed, or not operating freely. (v) Brakes do not fully release when release control is operated. |
(2) Emergency System-Performance: (a) Method. At a speed of 10 mph apply emergency brake firmly. Vehicle must come to a stop within a reasonable distance. (b) Method. Mount and level an approved decelerometer at centerline of vehicle. At a speed of 20 mph, apply emergency brake firmly. Observe decelerometer reading. | (2) (a) The vehicle fails to stop within a reasonable distance after emergency brake application. (b) A decelerometer reading of at least 6 feet per second per second cannot be obtained. |
Procedures: | Reject Vehicle If: |
(1) Set the parking brake firmly to determine the reserve travel of the hand lever or foot pedal. | (1) (a) There is less than 1/3 pedal or lever reserve remaining. (b) Brake fails to hold the vehicle on any grade on which it is operated. |
(2) Inspect the band or disc-type parking brake on the propeller (drive) shaft for the presence of oil or grease, condition of lining and adjustment. | (2) (a) There is oil or grease on the drum, disc, or lining. (b) The lining is worn through to the steel band or shoe. (c) The lining fails to make proper contact with the drum or disc when brake is applied. |
(3) Spring-type parking air brake system-inspect only for setting and release, not for travel reserve of the hand lever or foot pedal. | (3) Spring-type parking air brake system fails to set or release. |
Service Brake Systems | EmergencyBrake Systems | |||
I | II | III | IV | V |
Braking forceas a percentageof gross vehicleor combinationweight | Decelerationin feet persecond persecond | Applicationand brakingdistance infeet frominitial speedof 20 mph | Applicationand brakingdistance infeet frominitial speedof 20 mph | |
(1) Passenger-carrying vehicles. (a) Vehicles with a seating capacity of 10 persons or less, including driver, and built on a passenger car chassis. | 65.2 | 21 | 20 | 54 |
(b) Vehicles with a seating capacity of more than 10 persons, including driver, and built on a passenger car chassis; vehicles built on a truck or bus chassis and having a manufacturer's GVWR of 10,000 pounds or less. | 52.8 | 17 | 25 | 66 |
(c) All other passenger-carrying vehicles (including motorcycles). | 43.5 | 14 | 35 | 85 |
(2) Property-carrying vehicles. (a) Single unit vehicles having a manufacturer's GVWR of 10,000 pounds or less. | 52.8 | 17 | 25 | 66 |
(b) Single unit vehicles having a manufacturer's GVWR of more than 10,000 pounds except truck tractors. Combinations of a 2-axle towing vehicle and trailer having a GVWR of 3,000 pounds or less. All combinations of 2 or less vehicles in drive-away or tow-away operation. | 43.4 | 14 | 35 | 85 |
(c) All other property-carrying vehicles and combinations of property-carrying vehicles. | 43.5 | 14 | 40 | 90 |
Md. Code Regs. 11.14.04.03