§FMCSR.com
Historical textIn force on Oct. 1, 2012Source: annual CFR editions 2012–2016

§ 393.42 Brakes required on all wheels.

Wording in the annual edition revised as of Oct. 1, 2012, superseded February 19, 2026.

govinfo, 2012 edition ↗
Before Jan. 1, 2017 the record is one snapshot per annual CFR edition, revised as of October 1. This is the 2012 edition's wording. An amendment that took effect between Oct. 1, 2012 and Oct. 1, 2012 would not appear until the next edition, so check the citations below and the Federal Register for exact effective dates.
What changedOct. 1, 2011 wording → Oct. 1, 2012 wording+68 added−106 removedHide

Link(a) toEvery ancommercial amendmentmotor publishedvehicle atshall 76be FRequipped 56321,with Septbrakes acting on all wheels. 13This requirement also applies to certain motor vehicles being towed in a driveaway-towaway operation, 2011.as follows:
(a1) EveryAny commercial motor vehicle shalltowed beby equippedmeans withof brakesa actingtow-bar when another motor vehicle is full-mounted on allthe wheelstowed vehicle; and
(2) Any saddlemount configuration with a fullmount.
(b) Exception. (1) Trucks or truck tractors having three or more axles and manufactured before July 25, 1980, are not required to have brakes on the front wheels. However, these vehicles must meet the requirements of § 393.52.
(2) Motor vehicles being towed in a driveaway-towaway operation (including the last truck of triple saddle-mount combinations (see § 393.71(a)(3)) are not required to have operative brakes provided the combination of vehicles meets the requirements of § 393.52. This exception is not applicable to:
(i) Any motor vehicle towed by means of a tow-bar when another motor vehicle is full-mounted on the towed vehicle; and
(ii) Any combination of motor vehicles utilizing three or more saddle-mounts.
(3) Any semitrailer or pole trailer (laden or unladen) with a gross weight of 1,361 kg (3,000 pounds) or less which is subject to this part is not required to be equipped with brakes if the axle weight of the towed vehicle does not exceed 40 percent of the sum of the axle weights of the towing vehicle.
(4) Any full trailer or four-wheel pole trailer (laden or unladen) with a gross weight of 1,361 kg (3,000 pounds) or less which is subject to this part is not required to be equipped with brakes if the sum of the axle weights of the towed vehicle does not exceed 40 percent of the sum of the axle weights of the towing vehicle.
(5) Brakes are not required on the steering axle of a three-axle dolly which is steered by a co-driver.
(6) Loaded housemoving dollies, specialized trailers and dollies used to transport industrial furnaces, reactors, and similar motor vehicles are not required to be equipped with brakes, 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.
[Figure or graphic omitted. See the official source.]
[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]
Effective; Date Note:
At 76 FR 56321, Sept. 13, 2011, § 393.42 was amended by revising paragraphs (a) and (b)(2), effective October 13, 2011 . For the convenience of the user, the revised text is set forth as follows:]

49 CFR § 393.42 — Brakes required on all wheels.. Text in force on October 1, 2012. This wording effective October 1, 2012 to February 19, 2026. Source: govinfo, 2012 edition, https://www.govinfo.gov/app/details/CFR-2012-title49-vol5/CFR-2012-title49-vol5-sec393-42. Retrieved from FMCSR.com, https://fmcsr.com/reg/393.42?asof=2012-10-01, on October 26, 2026. Unofficial compilation; verify against the official source.

(a) Every commercial motor vehicle shall be equipped with brakes acting on all wheels. This requirement also applies to certain motor vehicles being towed in a driveaway-towaway operation, as follows:

(1) Any motor vehicle towed by means of a tow-bar when another motor vehicle is full-mounted on the towed vehicle; and

(2) Any saddlemount configuration with a fullmount.

(b) Exception. (1) Trucks or truck tractors having three or more axles and manufactured before July 25, 1980, are not required to have brakes on the front wheels. However, these vehicles must meet the requirements of § 393.52.

(2) Motor vehicles being towed in a driveaway-towaway operation (including the last truck of triple saddle-mount combinations (see § 393.71(a)(3)) are not required to have operative brakes provided the combination of vehicles meets the requirements of § 393.52.

(3) Any semitrailer or pole trailer (laden or unladen) with a gross weight of 1,361 kg (3,000 pounds) or less which is subject to this part is not required to be equipped with brakes if the axle weight of the towed vehicle does not exceed 40 percent of the sum of the axle weights of the towing vehicle.

(4) Any full trailer or four-wheel pole trailer (laden or unladen) with a gross weight of 1,361 kg (3,000 pounds) or less which is subject to this part is not required to be equipped with brakes if the sum of the axle weights of the towed vehicle does not exceed 40 percent of the sum of the axle weights of the towing vehicle.

(5) Brakes are not required on the steering axle of a three-axle dolly which is steered by a co-driver.

(6) Loaded housemoving dollies, specialized trailers and dollies used to transport industrial furnaces, reactors, and similar motor vehicles are not required to be equipped with brakes, 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.

[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]

Amendment history

6 distinct wordings on file since Oct. 1, 1996
  1. March 23, 2026 → presenteCFR, day-precisediff vs. previous
    [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; 91 FR 7890, Feb. 19, 2026]
  2. Feb. 19, 2026 → March 23, 2026eCFR, day-precisediff vs. previous
    [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]
  3. Oct. 1, 2012 → Feb. 19, 2026annual editions 2012–2016diff vs. previousviewing
    [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]
  4. Oct. 1, 2011 → Oct. 1, 2012annual edition 2011diff vs. previous
    [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]
  5. Oct. 1, 2005 → Oct. 1, 2011annual editions 2005–2010diff vs. previous
    [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]
  6. Oct. 1, 1996 → Oct. 1, 2005annual editions 1996–2004
    [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]

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.