Section 393.47 requires that the service brakes be capable of stopping the vehicle within the prescribed distance, and §393.47(e) sets the maximum readjustment limits for slack adjusters. Brakes exceeding the readjustment limit are out of adjustment.
Severity weight
A single brake out of adjustment is severity weight 4. Multiple out-of-adjustment brakes climb the weight ladder quickly. The 20% rule (under the North American OOS Criteria) places the vehicle out of service when 20% or more of the brakes on the vehicle are defective.
How to prevent it
- Run a stroke check at every annual inspection and at intervals consistent with your maintenance program.
- Train drivers to listen for unusual sounds and feel for pull during pre-trip brake tests.
- Replace shoes and adjust slacks before they reach the limit, not after.
- Use automatic slack adjusters but inspect them — automatic doesn't mean self-correcting.
How Roadworthy HQ helps
Brake-related findings in Roadworthy HQ trigger a vehicle-level alert, are logged against the maintenance record, and become part of the audit binder so corrective action is documented.