Brake Compliance: Why Brakes Are Your Biggest Exposure

Brakes account for more out-of-service violations than any other vehicle component. By a lot. Over 35% of all vehicle OOS orders are brake-related. If you do one thing to reduce your CSA vehicle maintenance score, focus on brakes.

The Adjustment Standard

For S-cam brakes (the most common type on trucks), the maximum allowable pushrod stroke depends on the brake chamber type and size. Inspectors measure this with the brakes applied.

• Type 30 chamber (long stroke): Max 2.0" stroke
• Type 30 chamber (standard): Max 2.0" stroke
• Type 24 chamber (long stroke): Max 2.0" stroke
• Type 20 chamber: Max 1.75" stroke

When more than 20% of the brakes on a vehicle or combination are out of adjustment, it's an OOS violation. On a typical 5-axle combination with 10 brakes, that means just 3 brakes out of adjustment = out of service.

Why Brakes Go Out of Adjustment

Normal drum wear. Every time the brakes are applied, the drum wears slightly, increasing the gap between shoe and drum. Automatic slack adjusters are supposed to compensate, but they don't always work perfectly — especially in cold weather or when contaminated with road debris.

The result: brakes that were in spec last month may be out of spec now. That's why checking at every PM — and ideally at every pre-trip — matters.

What Drivers Should Check

During pre-trip, drivers should:

1. Look at each brake chamber for any obvious issues (cracked, leaking, broken pushrod)
2. Listen for air leaks around brake chambers and glad hands
3. Check whether the parking brake holds the truck on a grade
4. If trained, perform a quick pushrod stroke check (apply brakes, measure travel)

Beyond Adjustment

Other brake violations that cause OOS orders:

• Brake hose chafing — rubber lines rubbing on frame, wearing through
• Air leaks — damaged diaphragms, loose fittings
• Contaminated linings — oil or grease on brake shoes
• Missing or loose components — missing cotter pins, cracked chambers
• Low air warning — buzzer or light not working below 60 PSI

A 10-minute brake check at every PM service. That's the investment. The return is avoiding the most common violation in the industry.