Table of Contents

§ 393.40 - required brake systems. § 393.41 - Parking brake system. § 393.42 - Brakes compelled on every wheels. § 393.43 - Breakaway and emergency braking. § 393.44 - former brake lines, protection. § 393.45 - Brake tubing and hoses; hose assemblies and also end fittings. § 393.46 - § 393.47 - Brake actuators, slack adjusters, linings/pads and drums/rotors. § 393.48 - Brakes to it is in operative. § 393.49 - control valves for brakes. § 393.50 - Reservoirs required. § 393.51 - Warning signals, wait pressure and vacuum gauges. § 393.52 - Brake performance. § 393.53 - automatically brake adjusters and brake convey indicators. § 393.55 - Antilock brake systems.

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(a) each commercial motor car must have brakes enough to stop and hold the car or mix of engine vehicles. Every commercial motor auto must fulfill the applicable service, parking, and also emergency brake system requirements detailed in this section.(b) organization brakes - (1) Hydraulic brake systems. Motor vehicles equipped with hydraulic brake systems and manufactured on or ~ September 2, 1983, must, in ~ a minimum, have a organization brake mechanism that meets the needs of FMVSS No. 105 in effect on the day of manufacture. Engine vehicles which to be not subject to FMVSS No. 105 ~ above the date of manufacture must have actually a organization brake mechanism that meets the applicable needs of §§ 393.42, 393.48, 393.49, 393.51, and 393.52 the this subpart.(2) waiting brake systems. Buses, trucks and also truck-tractors equipped v air brake systems and manufactured on or after March 1, 1975, and also trailers produced on or ~ January 1, 1975, must, in ~ a minimum, have actually a company brake mechanism that meets the requirements of FMVSS No. 121 in effect on the day of manufacture. Motor vehicles which were not topic to FMVSS No. 121 on the day of to produce must have actually a organization brake device that meets the applicable requirements of §§ 393.42, 393.48, 393.49, 393.51, and also 393.52 of this subpart.(3) Vacuum brake systems. Engine vehicles equipped with vacuum brake systems must have a organization brake device that meets the applicable demands of §§ 393.42, 393.48, 393.49, 393.51, and 393.52 that this subpart.(4) electrical brake systems. Motor vehicles equipped with electric brake solution must have a business brake device that meets the applicable demands of §§ 393.42, 393.48, 393.49 and 393.52 that this subpart.(5) rise brake systems. Motor vehicles equipped v surge brake equipment must have actually a service brake system that meets the applicable requirements of §§ 393.42, 393.48, 393.49, and 393.52 that this subpart.(c) Parking brakes. Every commercial motor automobile must it is in equipped v a parking brake device that meets the applicable requirements of § 393.41.(d) Emergency brakes - partial failure of company brakes - (1) Hydraulic brake systems. Motor vehicles manufactured on or after September 2, 1983, and equipped v a break-up service brake mechanism must, at a minimum, fulfill the partial failure needs of FMVSS No. 105 in effect on the day of manufacture.(2) air brake systems. Buses, trucks and truck tractors manufactured on or after ~ March 1, 1975, and trailers manufactured on or after January 1, 1975, should be equipped with an emergency brake device which, in ~ a minumum, meets the requirements of FMVSS No. 121 in effect on the date of manufacture.(3) Vehicles not subject to FMVSS Nos. 105 and also 121 on the day of manufacture. Buses, trucks and truck tractors not topic to FMVSS Nos. 105 or 121 on the day of produce must meet the demands of § 393.40(e). Trailers not subject to FMVSS No. 121 at the time of manufacture must fulfill the demands of § 393.43.(e) Emergency brakes, vehicles made on or after July 1, 1973. (1) A bus, truck, truck tractor, or a mix of motor vehicles manufactured on or after ~ July 1, 1973, and not covered under paragraphs (d)(1) or (d)(2) that this section, must have an emergency brake system which is composed of emergency functions of the service brake device or an emergency system separate native the service brake system. The emergency brake device must satisfy the applicable requirements of §§ 393.43 and 393.52.(2) A control by which the driver applies the emergency brake mechanism must be situated so the the driver can operate the from the common seating place while limit by any kind of seat belts through which the car is equipped. The emergency brake manage may be combined with either the business brake manage or the parking brake control. However, all three controls might not be combined.(f) Interconnected systems. (1) If the brake systems forced by § 393.40(a) are interconnected in any type of way, they need to be designed, constructed, and also maintained so that in the occasion of a failure of any component of the operating system of one or much more of the systems (except the business brake actuation pedal or valve), the motor car will have operative brakes and, for vehicles manufactured on or after ~ July 1, 1973, be capable of meeting the demands of § 393.52(b).(2) A motor vehicle to i beg your pardon the needs of FMVSS No. 105 (S5.1.2), handling partial failure of the organization brake, applied at the moment of manufacture meets the needs of § 393.40(f)(1) if the motor car is kept in conformity with FMVSS No. 105 and the motor auto is capable of meeting the demands of § 393.52(b), other than in the case of a structural fail of the brake understand cylinder body.(3) A bus is thought about to meet the requirements of § 393.40(f)(1) if the meets the requirements of § 393.44 and § 393.52(b).<70 FR 48048, Aug. 15, 2005, together amended at 72 FR 9870, Mar. 6, 2007>
(a) Hydraulic-braked vehicles made on or after ~ September 2, 1983. Each truck and bus (other than a college bus) with a GVWR the 4,536 kg (10,000 pounds) or less which is subject to this part and school buses through a GVWR better than 4,536 kg (10,000 pounds) shall be equipped v a parking brake system as compelled by FMVSS No. 571.105 (S5.2) in result at the moment of manufacture. The parking brake chandelier be capable of holding the vehicle or combination of vehicles stationary under any kind of condition that loading in which that is uncovered on a public road (free that ice and also snow). Hydraulic-braked vehicles which were not topic to the parking brake requirements of FMVSS No. 571.105 (S5.2) need to be equipped with a parking brake system that meets the requirements of i (c) the this section.(b) Air-braked strength units manufactured on or after March 1, 1975, and air-braked trailers made on or after January 1, 1975. Every air-braked bus, truck and truck tractor produced on and also after in march 1, 1975, and each air-braked trailer other than an agricultural commodity trailer, converter dolly, heavy hauler trailer or pulpwood trailer, shall it is in equipped v a parking brake mechanism as required by FMVSS No. 121 (S5.6) in impact at the moment of manufacture. The parking brake shall be capable of stop the car or mix of vehicles stationary under any condition that loading in which it is found on a public road (free of ice and snow). An agricultural commodity trailer, heavy hauler or pulpwood trailer shall carry sufficient chocking block to prevent movement when parked.(c) Vehicles not subject to FMVSS Nos. 105 and also 121 ~ above the day of manufacture. (1) each singly moved motor auto not topic to parking brake requirements of FMVSS Nos. 105 or 121 at the time of manufacturer, and also every combination of engine vehicles have to be equipped through a parking brake mechanism adequate to organize the automobile or mix on any grade top top which the is operated, under any type of condition that loading in which it is discovered on a public road (free that ice and also snow).(2) The parking brake system shall, at every times, be qualified of being used by either the driver"s muscular effort or by spring action. If other power is provided to apply the parking brake, there must be an accumulation of that power isolated from any type of common source and used solely for the procedure of the parking brake.Exception: This i shall not be applicable come air-applied, mechanically-held parking brake equipment which accomplish the parking brake demands of FMVSS No. 121 (S5.6).(3) The parking brake device shall be held in the used position by energy other than liquid pressure, waiting pressure, or electrical energy. The parking brake device shall no be capable of gift released uneven adequate power is accessible to immediately reapply the parking brake v the compelled effectiveness.<70 FR 48048, Aug. 15, 2005>
(a) Every advertising motor auto shall be equipped with brakes exhilaration on all wheels. This requirement likewise applies to particular motor vehicles being towed in a driveaway-towaway operation, together follows:(1) any kind of motor car towed by way of a tow-bar when an additional motor vehicle is full-mounted top top the towed vehicle; and(2) any kind of saddlemount configuration v a fullmount.(b) Exception. (1) trucks or van tractors having three or more axles and also manufactured before July 25, 1980, are not forced to have brakes top top the former wheels. However, these vehicles must fulfill the needs of § 393.52.(2) engine vehicles gift towed in a driveaway-towaway procedure (including the last truck the triple saddle-mount combinations (see § 393.71(a)(3)) room not forced to have actually operative brakes listed the mix of vehicles meets the demands of § 393.52.(3) any type of semitrailer or pole trailer (laden or unladen) through a gross load of 1,361 kg (3,000 pounds) or much less which is topic to this part is not compelled to it is in equipped v brakes if the axle load of the towed vehicle does not exceed 40 percent of the sum of the axle weights that the towing vehicle.(4) any kind of full trailer or four-wheel pole trailer (laden or unladen) v a gross weight of 1,361 kg (3,000 pounds) or much less which is topic to this part is not forced to it is in equipped through brakes if the amount of the axle weights that the towed car does not exceed 40 percent that the sum of the axle weights that the towing vehicle.(5) Brakes space not compelled on the steering axle that a three-axle dolly which is command by a co-driver.(6) invited housemoving dollies, specialized trailers and dollies supplied to transport industrial furnaces, reactors, and similar motor vehicles room not compelled to be equipped with brakes, detailed the rate at which the mix of vehicles will certainly be activate does no exceed 32 km/hour (20 mph) and also brakes on the combination of vehicles are qualified of stopping the mix within 12.2 meters (40 feet) native the rate at which the vehicle is being operated or 32 km/hour (20 mph), whichever is less.
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<52 FR 2803, Jan. 27, 1987, as amended at 53 FR 49398, Dec. 7, 1988; 54 FR 48617, Nov. 24, 1989; 59 FR 25574, may 17, 1994; 61 FR 1843, Jan. 24, 1996; 70 FR 48049, Aug. 15, 2005; 76 FR 56321, Sept. 13, 2011>
(a) Towing auto protection system. Every motor vehicle, if offered to tow a trailer equipped v brakes, shall be equipped v a means for giving that in the instance of a breakaway the the trailer, the business brakes top top the towing auto will be capable of protecting against the towing vehicle. Because that air braked towing units, the tractor protection valve or similar maker shall operate immediately when the air press on the towing auto is between 138 kPa and 310 kPa (20 psi and 45 psi).(b) Emergency brake requirements, waiting brakes. Every truck or van tractor equipped through air brakes, when provided for towing various other vehicles equipped through air brakes, shall it is in equipped v two means of activating the emergency functions of the trailer brakes. One of these method shall operate immediately in the occasion of palliation of the towing vehicle air supply to a fixed pressure which shall no be lower than 20 pounds per square customs nor greater than 45 pounds per square inch. The other method shall it is in a manually controlled machine readily operable by a human seated in the steering seat. That emergency place or method of operation shall be plainly indicated. In no instance may the manual way be so arranged regarding permit its use to prevent operation of the automatic means. The automatic and also manual means required by this section might be, yet are not forced to be, separate.(c) Emergency brake requirements, vacuum brakes. Every van tractor and also truck when supplied for towing other vehicles equipped v vacuum brakes, chandelier have, in addition to the single control required by § 393.49 to run all brakes the the combination, a second manual control maker which can be offered to operate the brakes top top the towed vehicles in emergencies. Such 2nd control shall be independent of brake air, hydraulic, and other pressure, and also independent of other controls, unless the braking system be so arranged the failure that the push on i beg your pardon the 2nd control counts will cause the towed automobile brakes to be applied automatically. The 2nd control is not compelled by this dominion to carry out modulated or i graduated braking.(d) Breakaway braking needs for trailers. Every trailer forced to it is in equipped with brakes shall have actually brakes which use automatically and immediately upon breakaway from the towing vehicle. Through the exception of trailers having three or an ext axles, all brakes with which the trailer is forced to be equipped have to be used upon breakaway from the towing vehicle. The brakes need to remain in the used position for at the very least 15 minutes.(e) Emergency valves. Waiting brake systems mounted on towed vehicles shall be so designed, by the use of “no-bleed-back” relay emergency valves or equivalent devices, that the it is provided reservoir supplied to administer air because that brakes shall be safeguarded against backflow of air to the towing automobile upon palliation of the towing vehicle air pressure.(f) Exception. The demands of paragraphs (b), (c) and (d) the this section shall no be applicable come commercial motor vehicles gift transported in driveaway-towaway operations.<53 FR 49384, Dec. 7, 1988, together amended at 70 FR 48050, Aug. 15, 2005>
On every bus, if equipped with air brakes, the braking system shall be so built that in the event any type of brake line to any type of of the front wheels is broken, the driver can use the brakes top top the behind wheels in spite of such breakage. The way used to use the brakes might be situated forward that the driver"s chair as lengthy as it can be activate manually through the driver once the driver is effectively restrained by any type of seat belt assembly listed for use. Every bus shall accomplish this necessity or comply through the regulations in result at the time of that manufacture.<53 FR 49400, Dec. 7, 1988>
(a) General construction requirements because that tubing and hoses, assemblies, and end fittings. Every brake tubing and hoses, brake water tap assemblies, and also brake hose end fittings must accomplish the applicable needs of FMVSS No. 106 (49 CFR 571.106).(b) Brake tubing and also hose installation. Brake tubing and hose have to - (1) be long and also flexible enough to accommodate without damage all normal motions of the components to which it is attached;(2) be secured versus chaffing, kinking, or other mechanical damage; and(3) Be mounted in a path that prevents it native contacting the vehicle"s exhaust system or any kind of other resource of high temperatures.(c) Nonmetallic brake tubing. Coiled nonmetallic brake tubing might be offered for connections in between towed and towing engine vehicles or between the structure of a towed vehicle and also the unsprung subframe of an adjustable axle the the motor auto if - (1) The coiled tubing has a directly segment (pigtail) in ~ each end that is at the very least 51 mm (2 inches) in length and is encased in a spring guard or similar an equipment which stays clear of the tubing indigenous kinking at the fitting at which it is attached to the vehicle; and(2) The feather guard or similar maker has at the very least 51 mm (2 inches) of close up door coils or similar surface at its user interface with the fitting and also extends at the very least 38 mm (11/2 inches) right into the coiled segment the the tubing native its directly segment.(d) Brake tubing and hose connections. All relationships for air, vacuum, or hydraulic braking solution shall be mounted so as to ensure one attachment totally free of leaks, constrictions or other conditions which would certainly adversely impact the power of the brake system.<70 FR 48050, Aug. 15, 2005>
(a) basic requirements. Brake contents must be constructed, installed and maintained to prevent too much fading and grabbing. The way of attachment and also physical attributes must administer for safe and also reliable avoiding of the commercial motor vehicle.(b) Brake chambers. The organization brake chambers and spring brake chambers top top each end of one axle must be the same size.(c) Slack adjusters. The reliable length that the slack adjuster ~ above each finish of an axle must be the same.(d) Linings and also pads. The thickness the the brake linings or pads shall accomplish the applicable needs of this i - (1) Steering axle brakes. The brake lining/pad thickness ~ above the steering axle that a truck, truck-tractor or bus shall not be much less than 4.8 mm (3/16 inch) at the shoe center for a shoe v a consistent strip the lining; much less than 6.4 mm (1/4 inch) at the shoe center for a shoe v two pads; or worn come the stay indicator if the lining is for this reason marked, for air drum brakes. The steering axle brake lining/pad thickness shall no be less than 3.2 mm (1/8 inch) for air disc brakes, or 1.6 mm (1/16 inch) or much less for hydraulic disc, drum and electric brakes.(2) Non-steering axle brakes. An air braked advertisement motor vehicle shall no be operated with brake lining/pad thickness much less than 6.4 mm (1/4 inch) or to the undertake indicator if the lining is so significant (measured at the shoe center for north brakes); or much less than 3.2 mm (1/8 inch) for disc brakes. Hydraulic or electrical braked commercial motor vehicles shall no be operated v a lining/pad thickness much less than 1.6 mm (1/16 inch) (measured at the shoes center) for disc or north brakes.(e) Clamp, Bendix DD-3, bolt-type, and also rotochamber brake actuator readjustment limits. (1) The pushrod stroke should not be higher than the values mentioned in the complying with tables:Clamp-Type Brake ChambersTypeOutside diameterBrake readjustment limit: conventional stroke chamberBrake readjustment limit: lengthy stroke chamber64 1/2 in. (114 mm)1 1/4 in. (31.8 mm)95 1/4 in. (133 mm)1 3/8 in. (34.9 mm)125 11/16 in. (145 mm)1 3/8 in. (34.9 mm)1 3/4 in. (44.5 mm).166 3/8 in. (162 mm)1 3/4 in. (44.5 mm)2 in. (50.8 mm).206 25/32 in. (172 mm)1 3/4 in. (44.5 mm)2 in. (50.8 mm).2 1/2 in. (63.5 mm).1247 7/32 in. (184 mm)1 3/4 in. (44.5 mm)2 in. (50.8 mm).2 1/2 in. (63.5 mm).2308 3/32 in. (206 mm)2 in. (50.8 mm)2 1/2 in. (63.5 mm).369 in. (229 mm)21/2 in. (63.5 mm)1 For kind 20 chambers v a 3-inch (76 mm) rated stroke.2 For form 24 chambers v a 3-inch (76 mm) rated stroke.Bendix DD-3 Brake ChambersTypeOutside diameterBrake readjustment limit308 1/8 in. (206 mm)2 1/4 in. (57.2 mm).Bolt-Type Brake ChambersTypeOutside diameterBrake readjustment limitA6 15/16 in. (176 mm)1 3/8 in. (34.9 mm).B9 3/16 in. (234 mm)1 3/4 in. (44.5 mm).C8 1/16 in. (205 mm)1 3/4 in. (44.5 mm).D5 1/4 in. (133 mm)1 1/4 in. (31.8 mm).E6 3/16 in. (157 mm)1 3/8 in. (34.9 mm).F11 in. (279 mm)2 1/4 in. (57.2 mm).G9 7/8 in. (251 mm)2 in. (50.8 mm).Rotochamber-Type Brake ChambersTypeOutside diameterBrake readjustment limit94 9/32 in. (109 mm)1 1/2 in. (38.1 mm).124 13/16 in. (122 mm)1 1/2 in. (38.1 mm).165 13/32 in. (138 mm)2 in. (50.8 mm).205 15/16 in. (151 mm)2 in. (50.8 mm).246 13/32 in. (163 mm)2 in. (50.8 mm).307 1/16 in. (180 mm)2 1/4 in. (57.2 mm).367 5/8 in. (194 mm)2 3/4 in. (69.9 mm).508 7/8 in. (226 mm)3 in. (76.2 mm).(2) for actuator types not listed in these tables, the pushrod stroke should not be higher than 80 percent that the rated stroke marked on the actuator through the actuator manufacturer, or greater than the readjustment limit marked on the actuator through the actuator manufacturer.(f) Wedge brake adjustment. The motion of the scribe note on the lining shall no exceed 1.6 mm (1/16 inch).(g) Drums and also rotors. The thickness the the north or rotors shall no be much less than the limits established through the brake north or rotor manufacturer.<70 FR 48051, Aug. 15, 2005, as amended at 77 FR 46638, Aug. 6, 2012; 86 FR 57076, Oct. 14, 2021>
(a) general rule. Other than as noted in paragraphs (b), (c), and (d) of this section, every brakes through which a motor auto is equipped need to at all times be capable of operating.(b) gadgets to reduce or eliminate front-wheel braking effort. A advertisement motor vehicle may be equipped v a an equipment to mitigate the former wheel braking effort (or in the instance of a three-axle van or van tractor manufactured prior to March 1, 1975, a machine to remove the front-wheel braking effort) if that maker meets the applicable needs of paragraphs (b)(1) and also (2) of this section.(1) Manually activate devices. Manually operated tools to minimize or eliminate front-wheel braking initiative may just be used on buses, trucks, and truck tractors manufactured prior to March 1, 1975. Such devices must no be offered unless the automobile is gift operated under adverse conditions such together wet, snowy, or icy roads.(2) automatic devices. Automatic devices must not minimize the front-wheel braking pressure by an ext than 50 percent the the braking force obtainable when the automatic machine is disconnected (regardless of whether or no an antilock device failure has arisen on any axle). The device must no be operable by the driver except upon application of the manage that activates the braking system. The maker must not be operable once the brake manage application press exceeds 85 psig (for vehicles equipped v air brakes) or 85 percent the the maximum system pressure (for vehicles which space not equipped through air brakes).(c) Exception. I (a) of this section does not apply to - (1) A towed car with disabling damages as identified in § 390.5;(2) A vehicle which is towed in a driveaway-towaway operation and is included in the exemption come the necessity for brakes on every wheels, § 393.42(b);(3) Unladen converter dollies through a gross weight of 1,361 kg (3,000 lbs) or less, and manufactured before March 1, 1998;(4) The steering axle of a three-axle dolly i m sorry is steered by a co-driver;(5) Loaded residence moving dollies, specialized trailers and dollies provided to transport commercial furnaces, reactors, and comparable motor vehicles listed the speed at which the mix of vehicles will be activate does not exceed 32 km/hour (20 mph) and brakes ~ above the mix of vehicles are qualified of preventing the combination within 12.2 meter (40 feet) native the rate at which the auto is gift operated or 32 km/hour (20 mph), whichever is less.(6) increased lift axles. Brakes on lift axles require not be qualified of being operated if the background axle is raised. However, brakes on lift axles should be qualified of being used whenever the lift axle is lowered and the tires call the roadway.(d) surging brakes. (1) rise brakes are allowed on:(i) any type of trailer with a gross auto weight rating (GVWR) of 12,000 pounds or less, when its GVWR does no exceed 1.75 times the GVWR that the towing vehicle; and(ii) any type of trailer with a GVWR greater than 12,000 pounds, yet less than 20,001 pounds, once its GVWR does no exceed 1.25 times the GVWR that the towing vehicle.(2) The gross auto weight (GVW) that a trailer equipped with surge brakes may be used instead of its GVWR to calculation compliance v the load ratios mentioned in i (d)(1) of this section when the trailer manufacturer"s GVWR label is missing.(3) The GVW the a trailer equipped with surge brakes must be offered to calculate compliance v the load ratios specified in paragraph (d)(1) the this section once the trailer"s GVW exceeds its GVWR.(4) The surging brakes must meet the needs of § 393.40.<70 FR 48051, Aug. 15, 2005, together amended at 72 FR 9870, Mar. 6, 2007>
(a) basic rule. Except as noted in paragraphs (b) and (c) that this section, every motor car manufactured after ~ June 30, 1953, which is equipped through power brakes, must have actually the braking mechanism so arranged that one application valve should when triggered cause all of the organization brakes ~ above the motor vehicle or combination motor automobile to operate. This requirement have to not be construed to prohibit engine vehicles from being fitted with an additional valve to be used to run the brakes on a trailer or trailers or as compelled for buses in § 393.44.(b) Driveaway-Towaway Exception. This section is not applicable come driveaway-towaway operations unless the brakes on together operations are designed to be activate by a single valve.(c) surge brake exception. This need is not applicable to trailers equipped v surge brakes that fulfill the conditions specified in § 393.48(d).<72 FR 9871, Mar. 6, 2007, together amended at 78 FR 58484, Sept. 24, 2013>
(a) Reservoir volume for air-braked power units made on or ~ March 1, 1975, and air-braked trailers manufactured on or after January 1, 1975. Buses, trucks, and truck-tractors produced on or after ~ March 1, 1975, and air-braked trailers produced on or ~ January 1, 1975, must meet the reservoir needs of FMVSS No. 121, S5.1.2, in effect on the day of manufacture.(b) Reservoir volume for air-braked vehicles not subject to FMVSS No. 121 on the day of manufacture and also all vacuum braked vehicles. Each motor auto using wait or vacuum braking must have actually either make reservation capacity, or a reservoir, that would permit the driver to do a full service brake application with the engine quit without exhausted the air pressure or vacuum below 70 percent of that indicated by the air or vacuum gauge immediately before the brake application is made. For the functions of this paragraph, a full organization brake application method depressing the brake pedal or treadle valve come the limit of its travel.(c) Safeguarding that air and vacuum. Each business reservoir device on a motor vehicle shall it is in protected against a lose of air push or vacuum as result of a failure or leakage in the system between the company reservoir and the resource of air push or vacuum, by check valves or equivalent devices whose suitable functioning can be confirm without disconnecting any kind of air or vacuum line, or fitting.(d) drain valves because that air braked vehicles. Every reservoir must have a condensate drainpipe valve that can be manually operated. Automatically condensate drain valves might be used detailed (1) they may be operated manually, or (2) a manual method of draining the reservoirs is retained.<70 FR 48052, Aug. 15, 2005>
(a) basic Rule. Every bus, truck and truck tractor, except as noted in paragraph (f), need to be equipped with a signal that offers a warning come the driver when a fail occurs in the vehicle"s organization brake system. The warning signal must satisfy the applicable demands of paragraphs (b), (c), (d) or (e) of this section.(b) Hydraulic brakes. Vehicles made on or after September 1, 1975, must accomplish the brake mechanism indicator lamp requirements of FMVSS No. 571.105 (S5.3) applicable come the vehicle on the day of manufacture. Vehicles produced on or after July 1, 1973 but prior to September 1, 1975, or come which FMVSS No. 571.105 was not applicable on the day of manufacture, must have a warning signal i m sorry operates prior to or upon application of the brakes in the event of a hydraulic-type complete failure that a partial system. The signal need to be one of two people visible in ~ the driver"s forward field of check out or audible. The signal must be continuous. (NOTE: FMVSS No. 105 was applicable to trucks and also buses native September 1, 1975 come October 12, 1976, and from September 1, 1983, come the present. FMVSS No. 105 was not applicable come trucks and also buses manufactured in between October 12, 1976, and also September 1, 1983. Engine carriers have the option of equipping those vehicles to fulfill either the indicator lamp demands of FMVSS No. 105, or the indicator lamp needs specified in this paragraph for vehicles which were not topic to FMVSS No. 105 top top the date of manufacture.)(c) waiting brakes. A advertisement motor automobile (regardless the the day of manufacture) fitted with organization brakes activated by compressed wait (air brakes) or a advertisement motor car towing a automobile with service brakes activated by compressed waiting (air brakes) should be equipped with a pressure gauge and also a warning signal. Trucks, van tractors, and buses produced on or after March 1, 1975, must, in ~ a minimum, have a pressure gauge and a warning signal i m sorry meets the needs of FMVSS No. 121 (S5.1.4 for the pressure gauge and S5.1.5 for the warning signal) applicable to the automobile on the date of produce of the vehicle. Power devices to i m sorry FMVSS No. 571.121 was no applicable on the date of manufacture of the auto must it is in equipped v - (1) A pressure gauge, clearly shows to a human seated in the typical driving position, which shows the air press (in kilopascals (kPa) or pounds every square customs (psi)) available for braking; and(2) A warning signal that is audible or visible to a human in the common driving position and also provides a consistent warning come the driver anytime the air push in the company reservoir system is in ~ 379 kPa (55 psi) and below, or one-half the the compressor branch cutout pressure, whichever is less.(d) Vacuum brakes. A advertisement motor automobile (regardless that the date it was manufactured) having company brakes set off by vacuum or a auto towing a automobile having service brakes caused by vacuum have to be equipped with - (1) A vacuum gauge, clearly shows to a human seated in the normal driving position, which indicates the vacuum (in millimeter or customs of mercury) accessible for braking; and(2) A warning signal the is audible or clearly shows to a human in the common driving position and provides a constant warning come the driver anytime the vacuum in the vehicle"s supply reservoir is less than 203 mm (8 inches) of mercury.(e) Hydraulic brakes used or assisted by wait or vacuum. Each car equipped with hydraulically activated service brakes i m sorry are applied or aided by compressed wait or vacuum, and also to i beg your pardon FMVSS No. 105 was not applicable ~ above the day of manufacture, should be equipped through a warning signal the conforms to i (b) the this ar for the hydraulic part of the system; i (c) the this section for the waiting assist/air used portion; or paragraph (d) that this ar for the vacuum assist/vacuum applied portion. This paragraph shall no be taken as request air pressure gauges or vacuum gauges, only warning signals.(f) Exceptions. The rules in paragraphs (c), (d) and also (e) of this section carry out not apply to residential or commercial property carrying commercial engine vehicles which have less than three axles and also (1) to be manufactured prior to July 1, 1973, and also (2) have a manufacturer"s gross vehicle weight rating less than 4,536 kg (10,001 pounds).

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<70 FR 48052, Aug. 15, 2005>
(a) Upon applications of its company brakes, a motor vehicle or mix of motor vehicles need to under any kind of condition that loading in which that is discovered on a public highway, be capable of - (1) developing a braking pressure at the very least equal come the percent of its gross weight stated in the table in paragraph (d) of this section;(2) Decelerating to a stop from 20 miles per hour in ~ not much less than the rate specified in the table in paragraph (d) the this section; and(3) avoiding from 20 miles every hour in a distance, measured indigenous the allude at which activity of the organization brake pedal or manage begins, the is not better than the distance specified in the table in i (d) the this section; or, for motor vehicles or motor car combinations that have a GVWR or GVW greater than 4,536 kg (10,000 pounds), (4) arising only the braking pressure specified in paragraph (a)(1) that this section and the protecting against distance mentioned in paragraph (a)(3) of this section, if braking force is measured by a performance-based brake tester i beg your pardon meets the needs of functional specifications because that performance-based brake testers for commercial engine vehicles, where braking force is the sum of the braking pressure at each wheel that the auto or vehicle mix as a percent of gross car or combination weight. (b) Upon application of its emergency brake system and with no various other brake device applied, a motor automobile or combination of engine vehicles must, under any condition of loading in which it is uncovered on a public highway, be qualified of protecting against from 20 miles per hour in a distance, measured from the point at which movement of the emergency brake control begins, the is not better than the distance mentioned in the table in i (d) that this section.(c) Conformity come the stopping-distance requirements of paragraphs (a) and also (b) that this ar shall be determined under the adhering to conditions:(1) any test need to be made with the vehicle on a difficult surface that is substantially level, dry, smooth, and cost-free of loose material.(2) The auto must be in the facility of a 12-foot-wide lane as soon as the check begins and also must not deviate from that lane during the test.(d) car brake performance table: type of motor auto Service brake equipment Emergency brake systems Braking pressure as a portion of gross auto or mix weight Deceleration in feet per 2nd per second Application and braking distance in feet indigenous initial speed at 20 mph Application and braking street in feet native initial rate of 20 mph A. Passenger-carrying vehicles: (1) Vehicles through a seating volume of 10 persons or less, including driver, and also built on a passenger automobile chassis65.2212054 (2) Vehicles through a seating capacity of an ext than 10 persons, including driver, and also built top top a passenger automobile chassis; vehicles developed on a van or bus chassis and having a manufacturer"s GVWR that 10,000 pounds or less52.8172566 (3) All other passenger-carrying vehicles43.5143585 B. Property-carrying vehicles: (1) solitary unit vehicles having a manufacturer"s GVWR the 10,000 pounds or less52.8172566 (2) single unit vehicles having actually a manufacturer"s GVWR of much more than 10,000 pounds, except truck tractors. Combine of a 2-axle towing vehicle and also trailer having a GVWR that 3,000 pounds or less. All combinations of 2 or much less vehicles in drive-away or tow-away operation43.5143585 (3) All various other property-carrying vehicles and combinations the property-carrying vehicles43.5144090 Notes: (a) there is a definite mathematical relationship in between the figures in columns 2 and 3. If the decelerations set forth in tower 3 are divided by 32.2 feet per-second per-second, the figures in shaft 2 will be obtained. (For example, 21 separated by 32.2 amounts to 65.2 percent.) shaft 2 is contained in the tabulation because details brake testing gadgets utilize this factor. (b) The decelerations mentioned in column 3 are an point out of the performance of the basic brakes, and as measure in practical brake trial and error are the best decelerations attained at part time throughout the stop. This decelerations together measured in brake tests cannot be provided to compute the worths in column 4 due to the fact that the deceleration is not continual at the same price over the entire period of the stop. The deceleration increases from zero come a maximum during a duration of brake system application and also brake-force buildup. Also, other determinants may cause the deceleration come decrease after reaching a maximum. The included distance the results because maximum deceleration is not continual is included in the figures in obelisk 4 however is not shown by the normal brake-testing tools for checking deceleration. (c) The ranges in pillar 4 and also the decelerations in shaft 3 are not straight related. “Brake-system application and also braking distance in feet” (column 4) is a definite measure up of the as whole effectiveness of the braking system, being the street traveled between the point at which the driver starts to relocate the braking controls and also the suggest at which the vehicle comes come rest. It consists of distance travel while the brakes room being applied and also distance traveled while the brakes are retarding the vehicle.(d) The street traveled during the duration of brake-system application and brake-force buildup varies with auto type, being negligible for countless passenger cars and also greatest for combinations of advertisement vehicles. This truth accounts because that the variation indigenous 20 to 40 feet in the values in column 4 because that the miscellaneous classes that vehicles.(e) The terms “GVWR” and also “GVW” refer to the manufacturer"s gross automobile weight rating and the really gross automobile weight, respectively.<36 FR 20298, Oct. 20, 1971, together amended at 37 FR 5251, Mar. 11, 1972; 37 FR 11336, June 7, 1972; 67 FR 51777, Aug. 9, 2002>