49 CFR § 393.53 - Automatic brake adjusters and brake adjustment indicators.

---
identifier: "/us/cfr/t49/s393.53"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "49 CFR § 393.53 - Automatic brake adjusters and brake adjustment indicators."
title_number: 49
title_name: "Transportation"
section_number: "393.53"
section_name: "Automatic brake adjusters and brake adjustment indicators."
chapter_name: "FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION"
subchapter_number: "B"
subchapter_name: "FEDERAL MOTOR CARRIER SAFETY REGULATIONS"
part_number: "393"
part_name: "PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "49 U.S.C. 31136, 31151, 31502; sec. 1041(b), Pub. L. 102-240, 105 Stat. 1914, 1993; secs. 5301 and 5524, Pub. L. 114-94, 129 Stat. 1312, 1543, 1560; and 49 CFR 1.87."
regulatory_source: "33 FR 19735, Dec. 25, 1968, unless otherwise noted."
cfr_part: "393"
---


# 393.53 Automatic brake adjusters and brake adjustment indicators.

(a) *Automatic brake adjusters (hydraulic brake systems).* Each commercial motor vehicle manufactured on or after October 20, 1993, and equipped with a hydraulic brake system, shall meet the automatic brake adjustment system requirements of Federal Motor Vehicle Safety Standard No. 105 (49 CFR 571.105, S5.1) applicable to the vehicle at the time it was manufactured.

(b) *Automatic brake adjusters (air brake systems).* Each commercial motor vehicle manufactured on or after October 20, 1994, and equipped with an air brake system must meet the automatic brake adjustment system requirements of Federal Motor Vehicle Safety Standard No. 121 (49 CFR 571.121, S5.1.8 or S5.2.2) applicable to the vehicle at the time it was manufactured.

(c) *Brake adjustment indicator (air brake systems).* On each commercial motor vehicle manufactured on or after October 20, 1994, and equipped with an air brake system which contains an external automatic adjustment mechanism and an exposed pushrod, the condition of service brake under-adjustment must be displayed by a brake adjustment indicator conforming to the requirements of Federal Motor Vehicle Safety Standard No. 121 (49 CFR 571.121, S5.1.8 or S5.2.2) applicable to the vehicle at the time it was manufactured.

[60 FR 46245, Sept. 6, 1995, as amended at 77 FR 46639, Aug. 6, 2012]