§393.52 sets the service-brake performance specifications: the vehicle must be capable of developing a braking force at least equal to the percentage of GVW set out in §393.52(b), and the service brake must stop the vehicle within the distance specified for the vehicle type and speed. Parking-brake performance is also specified — the vehicle must hold on the grade given in §393.52(d).
OOS
Performance failure measured by an inspector (commonly via a performance-based brake tester or a measured slow-down test) is an OOS condition. The vehicle may not continue from the inspection until performance is restored.
Severity weight
Severity weight 7 in the Vehicle Maintenance BASIC. The weight reflects how close a §393.52 failure is to a crash; this is the rule that catches the brakes that "kind of work" but cannot stop the vehicle.
How to prevent it
- Pair §393.47 adjustment checks with §393.52 performance tests; a vehicle within adjustment can still fail performance if linings are glazed or contaminated.
- Performance-based brake testers (PBBT) at the carrier's yard catch what stroke checks miss.
- Replace all brake hardware on an axle together — mixed hardware ages unevenly and degrades performance.
How Roadworthy HQ helps
§393.52 findings logged in Roadworthy HQ link to the vehicle alongside the related §393.47/§393.48 wheel-end data, block dispatch under §396.11(c), and surface against the §396 maintenance file for §385.337 corrective-action documentation.