Air-brake disc brakes use:
Correct. Disc brakes use a brake chamber and slack adjuster like S-cam drum brakes, but the force closes a caliper on a rotor instead of forcing shoes against a drum.
CDL Practice Question #148
Category: Air Brakes
Why this question matters
This question is one of 71 in our Air Brakes bank. The reasoning above comes directly from the AAMVA CDL Manual, the source document used by every U.S. state DMV. Memorizing the underlying rule — not just the letter answer — is what separates passing on the first attempt from a return trip and another fee.