§393.42(a) requires every CMV to be equipped with brakes acting on all wheels. Limited exceptions exist for certain trailers under 3,000 lb GVWR towed at the rear of another CMV, certain loaded house-moving dollies, and pre-1980 specific equipment. For everything operating commercially today, every wheel position has a brake.
OOS connection
§393.42 is the foundational requirement; §393.47 is the in-service standard the brakes must meet. The 20% rule (when 20% or more of the service brakes on the vehicle are defective, the vehicle is OOS) is in the NAS Out-of-Service Criteria and is the most-cited brake OOS condition.
Severity weight
Severity weight 4 in the Vehicle Maintenance BASIC. Brake findings have a multiplicative effect — §393.42, §393.47, §393.53 (slack adjusters), and §392.7 frequently appear together on the inspection report.
How to prevent it
- Annual inspection per §396.17 includes a brake-stroke check at every wheel position.
- Spread-trailer combinations (lift axles, certain doubles) — verify every dropped-axle position has its brake operating; lift-axle controls left in the up position can mask a non-functional brake.
- PM schedule includes brake-shoe replacement at the mileage interval recommended by the chassis manufacturer.
How Roadworthy HQ helps
A §393.42 brake citation is recorded with the inspection it came from. Roadworthy HQ does not record individual violation codes. Log the roadside inspection on the vehicle's Inspections tab: date, state, level, driver, the number of violations, and whether it was out-of-service. For an out-of-service inspection the 15-day §396.9(d)(3) repair-certification countdown stays on that tab until you enter the certification date. The rule's 15 days cover every violation on the report, not only out-of-service ones, so for a non-OOS inspection that date is yours to track. The repair itself goes in the vehicle's maintenance log: date, type, what was done, who did it, and cost. DVIRs are logged per vehicle with the defect described in your own words, and a defect marked safety-affecting that is logged without a repair certification sends a critical alert. The §396.17 annual inspection report uploads to the vehicle, with reminders 60, 30, and 7 days before the next one is due.