DOT brake violations: what 49 CFR 393.47 and 393.48 say and how they count on your CSA score

Brake violations on a roadside inspection are cited under a handful of federal rules: 49 CFR 393.47 (adjustment, linings, chambers and drums), 393.48 (brakes that do not work), 393.45 (hoses, tubing and leaks), 393.53 (automatic adjusters) and 396.3 (the general maintenance duty, which also carries the brakes out-of-service cite). All of them land in the Vehicle Maintenance BASIC of your CSA record. This guide quotes the two rules behind most brake cites word for word, shows how FMCSA’s Safety Measurement System (SMS) weighs them, and sets out what a DataQs challenge can and cannot fix.

Brake adjustment: the limits, word for word

49 CFR 393.47(e)(1): “The pushrod stroke must not be greater than the values specified in the following tables.” The limit depends on the chamber’s type and, for clamp-type chambers, on whether it is a standard stroke or long stroke chamber. From the clamp-type table:

• Type 16: 1 3/4 in. (44.5 mm) standard stroke; 2 in. (50.8 mm) long stroke.
• Type 20: 1 3/4 in. (44.5 mm) standard stroke; 2 in. (50.8 mm) long stroke, or 2 1/2 in. (63.5 mm) for a type 20 chamber with a 3-inch rated stroke.
• Type 24: 1 3/4 in. (44.5 mm) standard stroke; 2 in. (50.8 mm) long stroke, or 2 1/2 in. (63.5 mm) for a type 24 chamber with a 3-inch rated stroke.
• Type 30: 2 in. (50.8 mm) standard stroke; 2 1/2 in. (63.5 mm) long stroke.
• Type 36: 2 1/2 in. (63.5 mm).

The same paragraph has tables for Bendix DD-3, bolt-type and rotochamber-type chambers. For anything not in the tables, 393.47(e)(2) applies: “the pushrod stroke must not be greater than 80 percent of the rated stroke marked on the actuator by the actuator manufacturer, or greater than the readjustment limit marked on the actuator by the actuator manufacturer.” Wedge brakes have their own limit in 393.47(f): “The movement of the scribe mark on the lining shall not exceed 1.6 mm (1/16 inch).”

The rest of 393.47 covers:

• (b) and (c): “The service brake chambers and spring brake chambers on each end of an axle must be the same size” and “The effective length of the slack adjuster on each end of an axle must be the same.”
• (d): lining and pad thickness. On a steering axle with air drum brakes, not less than 3/16 in. at the shoe center for a continuous strip of lining, 1/4 in. for a shoe with two pads, or worn to the wear indicator; 1/8 in. for air disc brakes. On other axles of an air-braked vehicle, not less than 1/4 in. (or to the wear indicator) for drum brakes and 1/8 in. for disc brakes.
• (g): drums and rotors no thinner than the limits set by their manufacturer.

Brakes that must work, and the ones that need not

49 CFR 393.48(a): “Except as provided in paragraphs (b), (c), and (d) of this section, all brakes with which a motor vehicle is equipped must at all times be capable of operating.” The exceptions in 393.48(c) include a towed vehicle with disabling damage, certain driveaway-towaway vehicles, and this one, which matters to many fleets:

393.48(c)(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.”

Automatic adjusters have a build date. Under 393.53(b), “Each commercial motor vehicle manufactured on or after October 20, 1994, and equipped with an air brake system” must meet the automatic brake adjustment requirements of FMVSS No. 121 that applied when it was built; 393.53(c) sets the same date for brake adjustment indicators on adjusters with an exposed pushrod. Prove a build date from the vehicle’s certification label or its registration, not from a VIN decoder.

The brakes out-of-service cite: 396.3A1BOS

Many reports with brake problems carry an extra line: 396.3A1BOS, “BRAKES OUT OF SERVICE: The number of defective brakes is equal to or greater than 20% of the service brakes on the vehicle or combination.” FMCSA’s SMS Methodology explains that it “signifies an OOS condition based on the underlying violations noted under other cites.” In other words, the individual brakes are cited under their own codes (393.47, 393.48 and so on), and this line records that together they reached the out-of-service condition.

That changes where the out-of-service weight sits. In FMCSA’s current SMS data, 13 of the 167,011 rows for code 39347E (brake out of adjustment) are marked out of service. The out-of-service weight is on 396.3A1BOS, which carries a severity weight of 0 plus 2 for out of service. The 20% threshold comes from the CVSA out-of-service criteria, not from the CFR, so how the officer counted defective brakes follows the CVSA edition in force on the inspection date.

How a brake violation counts

• Which BASIC. Brake codes are in the Vehicle Maintenance BASIC, which uses violations from vehicle inspections (Levels 1, 2, 5 and 6) in the past 24 months.
• Severity. In FMCSA’s current SMS data, 39347E (brake out of adjustment) is in the “Brakes Out of Adjustment” group at severity 4, and it appears on more rows than any other 393.47 code. Most other brake codes, including inoperative brakes (393.48), lining, chamber and slack adjuster faults (393.47), hose and air leak faults (393.45) and automatic adjuster faults (393.53), are in “Brakes All Others”, also at 4. 396.3A1BOS is 0 + 2. A citation that ends in a conviction on a different charge drops to severity 1 (see your ticket was dismissed in court).
• Same code, one count. When the same violation is cited more than once on one inspection, the SMS uses it only once. Three brakes out of adjustment under 39347E count as one 39347E. Different codes count separately, and the total severity on one inspection in one BASIC is capped at 30.
• Time weight. The severity is multiplied by 3 for a violation in the last 6 months, 2 from 6 to 12 months, and 1 from 12 to 24 months. After 24 months it no longer counts.

Worked example (a hypothetical inspection, arithmetic on the rules above). Three months ago an officer cites two brakes out of adjustment (39347E), the brakes out-of-service line (396.3A1BOS) and an audible air leak at a connection (39345DB). That is 4 + 2 + 4 = 10, times a time weight of 3 = 30 toward your Vehicle Maintenance measure. The second out-of-adjustment brake adds nothing, because the same code counts once. Thirteen months after the inspection the same lines count 10 × 1 = 10. The measure divides these points by the time weight of all your relevant inspections, clean ones included; see what is a CSA score?

Before you challenge: what a reviewer can act on

1. Check the unit is yours. Match the VIN and plate on the report against your registrations and leases. A unit that belongs to another carrier is a different kind of request: an inspection on your record that isn’t yours.
2. Compare the recorded stroke with the limit. If the report records a pushrod stroke and a chamber type, check them against the 393.47(e) table. A recorded stroke at or under the limit for the recorded chamber does not exceed it, and the report then contradicts its own violation. If the chamber is a long stroke chamber and the report does not say so, the long stroke limit applies, and the proof is the chamber’s own marking, shown on the unit the report names. A report that simply records no measurement is different: the reviewer can ask the officer, so a missing detail is usually not enough.
3. Read the exceptions. An inoperative-brake cite under 393.48(a) on a lift axle that the report or the officer’s notes show was raised is outside the rule (393.48(c)(6)). An automatic adjuster cite under 393.53 on a vehicle built before 20 October 1994 is outside that section; prove the build date from the certification label or registration.
4. Follow the out-of-service line. 396.3A1BOS depends on the brake cites under it. If you challenge an underlying brake violation, ask in the same request for the reviewer to check whether the brakes out-of-service line still stands without it.
5. Count the repeats. Because one code counts once per inspection, correcting one of three brakes cited under 39347E leaves the violation in place at full weight. Every instance has to be wrong, each for its own documented reason.
6. Know what a repair receipt proves. A receipt for a brake adjusted or replaced after the inspection shows you fixed it. It does not show the brake met the rule at the roadside, so it does not contradict the report.
7. File it properly. A request that carries its own proof, attached on the first submission: how to dispute a DOT violation and file a DataQ.

If none of these applies and the report is accurate, a challenge will not remove the violation. It loses weight at 6 and 12 months and stops counting at 24.

Sources

• 49 CFR 393.47, Brake actuators, slack adjusters, linings/pads and drums/rotors (eCFR, current to 9 October 2026; last amended 86 FR 57076, 14 October 2021): paragraphs (b) to (g) and the clamp-type table, quoted above.
• 49 CFR 393.48, Brakes to be operative (eCFR, current to 9 October 2026): paragraphs (a) and (c)(6).
• 49 CFR 393.53, Automatic brake adjusters and brake adjustment indicators (eCFR, current to 9 October 2026): paragraphs (b) and (c).
• FMCSA, Safety Measurement System (SMS) Methodology, Version 3.21 (methodology revised May 2026): Vehicle Maintenance BASIC, pp. 3-13 to 3-15 (relevant inspections, one cite per inspection, OOS weight of 2, cap of 30, time weights); Appendix B, pp. B-15 and B-16, Table B-8 (396.3A1BOS, severity 0 + 2, in the SMS from 1 April 2017).
• FMCSA, “SMS Input – Violation” dataset, data.transportation.gov: the violation codes beginning 39343, 39345, 39347, 39348, 39353 and 3963A1B, their descriptions, BASIC, violation group, severity weight and out-of-service flag, read 14 October 2026.