Air Disc Brakes Drew 97 of 141 Drum and Rotor Violations in CVSA's Brake Week

Ninety-seven of the drum-and-rotor violations were on air disc brakes, 36 on S-cam drum brakes and eight on hydraulic systems. Sixty-four vehicles were parked on those findings — a drum or rotor violation does not automatically sideline a truck.

The largest single category was rusted rotors, at 48. Broken drums came second at 36, and every one of those was on an S-cam system. Broken rotors accounted for 33 and metal-to-metal contact for 24, per the category breakdown CVSA published with the results.

One caveat before anyone reads this as an indictment of air disc: CVSA did not publish what share of the inspected fleet was running ADB, so 97 versus 36 is a count, not a defect rate.

Rust leading the list is the result that should change a shop's routine. Scale forms quickly on an exposed rotor face once a unit stops turning wheels — a trailer dropped in a yard through a wet month, seasonal equipment, spare power sitting between drivers. Light surface rust burnishes off in the first few stops. Pitting and heavy scale do not, and an inspector reading a corroded friction surface at roadside is not going to split that hair for you.

The rest of the campaign broke along familiar lines. Half the out-of-service vehicles — 1,176 — met the 20% defective brake criterion, brake hoses and tubing produced 600 violations, air loss rate 145, other steering axle conditions 119 and steering axle linings 92. Twelve U.S. jurisdictions ran performance-based brake testers on 657 vehicles; 29 of them, 4.41%, failed to hit the 43.5% minimum braking efficiency.

The 2027 Brake Safety Week is set for April 18-24, which gives fleets five months and a winter in between — the exact conditions that produced the rust column.

Pull wheels on anything that has been parked more than a few weeks and look at rotor faces before the unit goes back in service, not after. That is most urgent on air-disc-equipped tractors, now common on current Cascadia, T680, 579, VNL and Anthem builds, where the rotor is the wear part you cannot see through the wheel. On S-cam equipment the failure mode was different and blunter: 36 cracked drums, which is a replacement, not an adjustment.

Hoses and tubing at 600 violations deserve the same walk-around attention; routing and condition are cheap to fix in a bay and expensive at a scale house. If you are pricing the replacements, check the interchange on the rotor or drum number before you order rather than defaulting to the dealer part, and confirm which model years came with air disc versus S-cam on mixed fleets where the spec changed mid-generation. Where a truck is pulling or showing uneven wear rather than failing outright, the symptom-by-symptom brake diagnostics will narrow it before you start replacing hardware.