§FMCSR.com
Historical textIn force on Oct. 1, 2005Source: annual CFR editions 2005–2006

§ 393.48 Brakes to be operative.

Wording in the annual edition revised as of Oct. 1, 2005, superseded by the 2007 annual edition.

govinfo, 2005 edition ↗
Before Jan. 1, 2017 the record is one snapshot per annual CFR edition, revised as of October 1. This is the 2005 edition's wording. An amendment that took effect between Oct. 1, 2005 and Oct. 1, 2005 would not appear until the next edition, so check the citations below and the Federal Register for exact effective dates.
What changedOct. 1, 2003 wording → Oct. 1, 2005 wording+264 added−150 removedHide

(a) General rule. Except as provided in paragraphs (b) and (c) of this section, all brakes with which a commercial motor vehicle is equipped must be operable at all times be capable of operating.
(b) Devices to reduce or remove front-wheel braking effort. A commercial motor vehicle may be equipped with a device to reduce the front wheel braking effort upon its front wheels (or, in the case of a three-axle truck or truck tractor manufactured before March 1, 1975, a device to remove the front-wheel braking effort) upon its front wheels, if that device conformsmeets to, and is used in compliance with, the rulesapplicable inrequirements paragraphof paragraphs (b) (1) orand (2) of this section.
(1) Manually operated devices. AManually manually operated devicedevices to reduce or remove the front-wheel braking effort mustmay notonly be—
(i) Installedused inon a motor vehicle other than a busbuses, trucktrucks, orand truck tractor;tractors or
(ii) Installed in a bus, truck, or truck tractor manufactured afterbefore FebruaryMarch 281, 1975;. or
(iii)Such Useddevices inmust thenot reducedbe modeused exceptunless when the vehicle is operatingbeing operated under adverse conditions such as wet, snowy, or icy roads.
(2) Automatic devices. AnAutomatic automaticdevices devicemust tonot reduce the front-wheel braking effortforce by upmore tothan 50 percent of the normal braking force, available when the automatic device is disconnected (regardless of whether or not an antilock system failure has occurred on any axle,). The device must not—
(i) Bebe operable by the driver except upon application of the control that activates the braking system;. and
(ii)The Bedevice must not be operable when the pressure that transmits brake control application forcepressure exceeds—
(A) 85 psig on(for air-mechanicalvehicles brakingequipped systems;with or
(Bair brakes) or 85 percent of the maximum system pressure in(for the case of vehicles utilizingwhich otherare thannot compressedequipped with air brakes).
(c) Towed vehicleException. Paragraph (a) of this section does not apply to—
(1) A disabledtowed vehicle beingwith towed;disabling ordamage as defined in § 390.5;
(2) A vehicle beingwhich is towed in a driveaway-towaway operation whichand is exemptincluded fromin the generalexemption ruleto ofthe §requirement for brakes on all wheels, § 393.42(b);
(3) underUnladen paragraphconverter dollies with a gross weight of 1,361 kg (b3,000 lbs) or less, and manufactured prior to March 1, 1998;
(4) The steering axle of thata section.three-axle dolly which is steered by a co-driver;
[39(5) FRLoaded 26907house moving dollies, Julyspecialized 24trailers and dollies used to transport industrial furnaces, 1974reactors, asand amendedsimilar motor vehicles provided the speed at 41which FRthe 29130,combination Julyof 15,vehicles 1976;will 41be FRoperated 53031does not exceed 32 km/hour (20 mph) and brakes on the combination of vehicles are capable of stopping the combination within 12.2 meters (40 feet) from the speed at which the vehicle is being operated or 32 km/hour (20 mph), Decwhichever is less.
(6) 3Raised lift axles. Brakes on lift axles need not be capable of being operated while the lift axle is raised. However, 1976;brakes 67on lift axles must be capable of being applied whenever the lift axle is lowered and the tires contact the roadway.
[70 FR 6182448051, OctAug. 215, 20022005]

49 CFR § 393.48 — Brakes to be operative.. Text in force on October 1, 2005. This wording effective October 1, 2005 to October 1, 2007. Source: govinfo, 2005 edition, https://www.govinfo.gov/app/details/CFR-2005-title49-vol5/CFR-2005-title49-vol5-sec393-48. Retrieved from FMCSR.com, https://fmcsr.com/reg/393.48?asof=2005-10-01, on October 26, 2026. Unofficial compilation; verify against the official source.

(a) General rule. Except as provided in paragraphs (b) and (c) of this section, all brakes with which a commercial motor vehicle is equipped must be operable at all times.

(b) Devices to reduce or remove front-wheel braking effort. A commercial motor vehicle may be equipped with a device to reduce the front wheel braking effort (or in the case of a three-axle truck or truck tractor manufactured before March 1, 1975, a device to remove the front-wheel braking effort) if that device meets the applicable requirements of paragraphs (b)(1) and (2) of this section.

(1) Manually operated devices. Manually operated devices to reduce or remove front-wheel braking effort may only be used on buses, trucks, and truck tractors manufactured before March 1, 1975. Such devices must not be used unless the vehicle is being operated under adverse conditions such as wet, snowy, or icy roads.

(2) Automatic devices. Automatic devices must not reduce the front-wheel braking force by more than 50 percent of the braking force available when the automatic device is disconnected (regardless of whether or not an antilock system failure has occurred on any axle). The device must not be operable by the driver except upon application of the control that activates the braking system. The device must not be operable when the brake control application pressure exceeds 85 psig (for vehicles equipped with air brakes) or 85 percent of the maximum system pressure (for vehicles which are not equipped with air brakes).

(c) Exception. Paragraph (a) of this section does not apply to—

(1) A towed vehicle with disabling damage as defined in § 390.5;

(2) A vehicle which is towed in a driveaway-towaway operation and is included in the exemption to the requirement for brakes on all wheels, § 393.42(b);

(3) Unladen converter dollies with a gross weight of 1,361 kg (3,000 lbs) or less, and manufactured prior to March 1, 1998;

(4) The steering axle of a three-axle dolly which is steered by a co-driver;

(5) Loaded house moving dollies, specialized trailers and dollies used to transport industrial furnaces, reactors, and similar motor vehicles provided the speed at which the combination of vehicles will be operated does not exceed 32 km/hour (20 mph) and brakes on the combination of vehicles are capable of stopping the combination within 12.2 meters (40 feet) from the speed at which the vehicle is being operated or 32 km/hour (20 mph), whichever is less.

(6) Raised lift axles. Brakes on lift axles need not be capable of being operated while the lift axle is raised. However, brakes on lift axles must be capable of being applied whenever the lift axle is lowered and the tires contact the roadway.

[70 FR 48051, Aug. 15, 2005]

Amendment history

4 distinct wordings on file since Oct. 1, 1996
  1. Oct. 1, 2007 → presentannual editions 2007–2016diff vs. previous
    [70 FR 48051, Aug. 15, 2005, as amended at 72 FR 9870, Mar. 6, 2007]
  2. Oct. 1, 2005 → Oct. 1, 2007annual editions 2005–2006diff vs. previousviewing
    [70 FR 48051, Aug. 15, 2005]
  3. Oct. 1, 2003 → Oct. 1, 2005annual editions 2003–2004diff vs. previous
    [39 FR 26907, July 24, 1974, as amended at 41 FR 29130, July 15, 1976; 41 FR 53031, Dec. 3, 1976; 67 FR 61824, Oct. 2, 2002]
  4. Oct. 1, 1996 → Oct. 1, 2003annual editions 1996–2002
    [39 FR 26907, July 24, 1974, as amended at 41 FR 29130, July 15, 1976; 41 FR 53031, Dec. 3, 1976]

A new entry appears whenever the regulatory words change between government snapshots. Day-precise from the eCFR (2017 onward); before that, one snapshot per annual CFR edition (revised as of October 1). Bracketed citations are the Federal Register history printed with the section.