Code of Maryland Regulations › Title 11 - DEPARTMENT OF TRANSPORTATION › Subtitle 14 - MOTOR VEHICLE ADMINISTRATION-VEHICLE INSPECTIONS › Chapter 11.14.05 - Safety Standards for Trailers › Section 11.14.05.04 - Brakes

Current through Register Vol. 51, No. 14, July 12, 2024
Trailers 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.
Click
				  here to view Image
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.