Brake adjustment limit checker

The limits, from 49 CFR 393.47(e)

Pushrod stroke must not be greater than these readjustment limits. The most common chambers on trucks and trailers:

The checker also includes types 6 and 9, the DD-3 type 30 (2 1/4 in) and rotochambers 16 to 36.

Source: 49 CFR 393.47 (Cornell LII) · checked 2026-10

How the checker decides

For each wheel position: OK if the measured stroke is under the chamber's limit, AT LIMIT if it equals the limit (due for readjustment), and PAST LIMIT if it's greater. The summary counts brakes past the limit and their share of all the brakes you entered. Inspectors use counts like that when deciding whether a truck goes out of service.

Worked example

One of ten brakes past the limit: 10%. That's a violation and needs fixing before the truck moves, even before it reaches any out-of-service count.

Measuring stroke

Mark each pushrod at the chamber face with the brakes released, apply the brakes fully with adequate air pressure, and measure how far the mark moved. A helper on the pedal makes it a two-minute job per axle. Always chock the wheels and follow your shop's safety procedure.

Why it matters

Out-of-adjustment brakes lengthen stopping distance and are a common roadside inspection violation. An out-of-service order costs you the load, the appointment and often the broker. Clean inspections also matter during the new entrant safety audit in your first year.