Md. Code Regs. 11.14.05.04
Current through Register Vol. 51, No. 20, October 4, 2024
Section 11.14.05.04 - BrakesTrailers and semitrailers to be registered up to 3,000 pounds GVWR are not required to be equipped with brakes. However, if such a trailer or semitrailer is equipped with brakes, all brakes shall meet minimum standards. Trailers and semitrailers to be registered from 3,001 pounds GVWR to 10,000 pounds GVWR shall be equipped with brakes on all wheels of at least one axle. Trailers and semitrailers to be registered over 10,000 pounds GVWR shall have brakes on all wheels. At least one wheel and drum shall be removed from each axle equipped with drum brakes. On disc brakes only wheel assembly removal is necessary. On trailers and semitrailers with brakes on more than one axle, wheel assembly removal shall be on alternate sides. Always inspect a brake assembly which shows evidence of leaking fluid or grease.
A. Drums and Discs. | Procedures: | Reject Vehicle If: |
| (1) Brake Drums: (a) Inspect the condition of the drum friction surface for any crack extending to the open edge of the drum (short hairline heat cracks should not be considered). (b) Inspect for any crack on the outside of the drum. (c) Inspect for mechanical damage. (d) Inspect for contaminated friction surface. (e) Measure inside diameter of drum. | (1) (a) There is a crack on the friction surface extending to the open edge of the drum. (b) There is any external crack. (c) There is evidence of excessive mechanical damage other than wear. (d) The friction surface is contaminated with oil, grease, or brake fluid. (e) The inside drum diameter is greater than the manufacturer's recommended limit or the diameter stamped on the drum, or if the drum is not stamped, the manufacturer's maximum allowable remachining specification. If the drum is not stamped and no manufacturer's specification exists and the original diameter of the drum can be determined, the inside diameter may be no more than 0.090 inch greater than the original diameter. |
| (2) Brake Discs (if equipped): (a) Inspect for any crack extending to the edge of the disc. (b) Inspect for mechanical damage. (c) Inspect for contaminated friction surface. | (2) (a) There is any crack extending to the edge of the disc. (b) If a crack extends into a weld or more than one-half the outside diameter of a BF Goodrich steel disc. (c) There is evidence of excessive mechanical damage other than wear. (d) The friction surface is contaminated with oil, grease, or brake fluid. (e) The thickness of the disc is less than the manufacturer's recommended limit or the thickness stamped on the disc. |
B. Brake Linings or Pads. | Procedures: | Reject Vehicle If: |
| (1) Condition of Linings and Pads: (a) Bonded linings: Measure the lining thickness at the thinnest point. (b) Riveted linings: (i) Inspect for loose or missing rivets; (ii) Measure lining thickness above rivet head at thinnest point. (c) Wire backed linings: Inspect for wire showing in the friction surface. (d) Bolted linings: (i) Inspect for loose or missing bolts; (ii) Measure lining thickness 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. (f) Pads (disc brakes): Inspect thickness of friction pads. | (1) (a) Thinnest point of remaining bonded lining is less than 2/32 inch. (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 backing is visible in the friction surface. (d) Bolted linings: (i) Any fastening parts are loose or missing; (ii) Remaining lining is less than 5/16 inch at center of shoe. (e) (i) Lining is broken, cracked, or not firmly and completely attached to shoe. (ii) Friction surface is contaminated with oil, grease, or brake fluid. (iii) Lining wear is extremely uneven. (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. |
C. Mechanical Linkage. | Procedures: | Reject Vehicle If: |
| (1) Condition of mechanical components: (a) Inspect for worn pins and missing or defective cotter pins. (b) Inspect for broken, missing, or worn springs, cables, clevises, couplings, rods, and anchor pins. (c) Inspect for frozen, rusted, or inoperative connections, missing, spring clips, and defective grease retainers. (d) Inspect for restriction of shoe movement at backing plate and for binding between brake shoes and anchor pins. | (1) (a) Mechanical parts are missing, broken, or badly worn. (b) Grease retainers are leaking (dampness is not cause for rejection). (c) Conversion of a self-adjusting mechanism that is not completely converted. |
D. Hydraulic System. | Procedures: | Reject Vehicle If: |
| (1) Visually inspect condition of hydraulic system: (a) Inspect wheel cylinders for leakage and operation. Do not remove dust covers. Leakage can be determined by pushing on the outside of the boot. (b) Inspect hydraulic hoses and brake lines for leaks, cracks, chafing, flattened or restricted sections, and improper support. (c) Inspect master cylinder for leakage and fluid level (be sure no dirt gets into reservoir when cover is removed and that gasket is serviceable). | (1) (a) Any wheel cylinder leaks. (b) Any wheel cylinder fails to operate. (c) Brake hoses or brake lines are cracked, chafed, flattened, restricted; are rusted and pitting is visible; are not securely fastened or lines have not been repaired or replaced with copper tubing or other material not specifically designed for use as hydraulic brake lines. Hoses or brake lines are mounted to contact wheels or body during suspension movement. (d) Master cylinder leaks. (e) Master cylinder fluid level is less than 1/2 full in any section. (f) Master cylinder gasket does not properly seal. |
| (2) If the vehicle is equipped with hydraulic surge brakes, test for functions of brakes by causing brakes to be applied. | (2) (a) Brakes fail to function. (b) Brakes do not remain applied until released. |
E. Air Brake Leakage. Before conducting these inspections, it may be desirable to install in the system an air gauge (0-150 psi) which has 5 or 10 psi increments, so that small changes in pressure can be more easily observed. Also, to eliminate the possibility of leakage being in the system of the towing vehicle, conduct air leakage tests on the uncoupled towing vehicle before inspecting the system of the trailer or semitrailer. | Procedures: | Reject Vehicle If: |
| (1) Air leakage in system: Connect trailer or semitrailer air brake system to towing vehicle or independent air supply and inspect for air leakage in two ways: (a) With a fully charged system or independent air supply and record the pressure drop in psi per minute with brakes fully applied; (b) With a fully charged system or independent air supply and record pressure drop in psi per minute with brakes released. | (1) Leakage exceeds the following limits: (a) Brakes fully applied-4 psi per minute (b) Brakes released-3 psi per minute. |
| (2) General condition: (a) Inspect all air hoses, tubes and connections. Check attachment of all connecting lines and look for proper supporting parts. Be sure lines are free from contact with frame, axles, wheels, or other lines. (b) Inspect for leaks that may be heard from valves, diaphragms, piston cups, and connections. | (2) (a) There are leaks, breaks, crimps, or cracks in the air hoses, tubes, or connections. (b) Lines are being chafed by moving parts, frame, or other lines. (c) Leaks in valves, diaphragms, piston cups, or connections can be heard. |
F. Vacuum System. | Procedures: | Reject Vehicle If: |
| (1) Condition of vacuum 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 flying debris or rubbing. |
| (2) Operation of vacuum system: Couple trailer or semitrailer to a vacuum supply and open shutoff valves. Then: (a) If motor vehicle is used, start engine and allow about 1 minute to build vacuum; (b) Apply and release brake pedal a number of times and observe action of brake chamber rods. | (2) (a) Brake chamber rod does not move when brakes are applied or released. (b) Rods do not reach full released position. |
G. Actuator Reserve. | 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 Travel Limits Chart. (b) 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° with brakes applied. |
| (3) Wedge brake shoe movement: Measure total shoe movement from released to applied positions. | (3) Brake shoe movement on wedge brakes exceeds 1/16 inch. |
Figure 1, chart and diagram.
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H. Electric Brakes. Electric brakes are generally used on small and occasionally on large commercial trailers and semitrailers. | Procedures: | Reject Vehicle If: |
| (1) Electric brakes-function: (a) Insert a low range DC ammeter into the circuit between the controller and brakes. Ammeter should read "zero" with controller in off position. Gradually apply controller to full "On" position and take maximum ammeter reading. (b) Gradually return controller to full "Off" position. Ammeter should return to "zero". Divide the maximum ammeter reading by the number of brakes. (c) Inspect for loose or corroded terminal connections and broken, frayed, or unsupported wires. | (1) (a) The maximum amperage per brake is: (i) More than 20 percent above; or (ii) More than 30 percent below brake manufacturer's maximum current rating. (b) Electric terminals are loose or excessively corroded. (c) Wires or connectors are broken, frayed, or not properly supported. |
I. Emergency Brake. Every trailer, semitrailer, and pole trailer equipped with air or vacuum actuated brakes and every trailer, semitrailer, and pole trailer with a registered gross weight in excess of 3,000 pounds, manufactured or assembled after June 1, 1970, shall be equipped with brakes of a character to be applied automatically and promptly and remain applied for at least 15 minutes on breakaway from the towing vehicle. | Procedures: | Reject Vehicle If: |
| (1) Air or vacuum emergency brakes: (a) Couple trailer or semitrailer to fully charged air or vacuum system. Then: (i) Disconnect couplings and observe for automatic application of trailer or semitrailer brakes; (ii) Observe operating mechanism for "bottoming" before brakes are fully applied; (iii) Record length of time brakes remain applied. (b) If manual control for trailer or semitrailer emergency brake system is installed: (i) Connect trailer or semitrailer couplings and build up the system to governor cut-out point; (ii) Stop engine and operate control-observe emergency brake application and release; (iii) Make a series of brake applications and observe automatic trailer or semitrailer brake application. | (1) (a) Emergency brakes do not automatically apply. (b) Operating mechanism "bottoms" before brakes are fully applied. (c) Brakes do not remain applied for at least 15 minutes. (d) With manual control, brakes do not apply and release by operating manual control. (e) Air only: Brakes apply automatically when reservoir pressure is above 45 psi or fail to apply automatically when pressure is reduced within range of 45-20 psi. |
| (2) Electric emergency brakes: Place a DC ammeter in the emergency brake power supply lines. Disconnect all electrical connections between the towing vehicle and the trailer or semitrailer. Then: (a) Operate breakaway switch and observe application of trailer or semitrailer brakes; (b) Operate ammeter reading and divide by the number of brakes; (c) Connect electric cables, return safety switch to normal position, and observe release of trailer or semitrailer brakes. | (2) (a) Brakes do not apply automatically when breakaway safety switch is operated. (b) Brakes do not release when switch is returned to normal position. (c) Brakes do not receive at least 50 percent of manufacturer's maximum current (amperes) rating per brake. |
| (3) Hydraulic surge emergency brakes. Inspection for operation of breakaway device, if equipped, application of trailer or semitrailer brakes and record length of time brakes remain applied. | (3) (a) Breakaway device, if equipped, fails to operate. (b) Brakes would not apply upon breakaway. (c) Brakes do not remain applied for at least 15 minutes. |
Md. Code Regs. 11.14.05.04
Regulations .04 Safety Standards for Trailers adopted effective October 31, 1988 (15:22 Md. R. 2557)