Disc Thickness Variation — the difference between the thickest and thinnest points on the braking surface.

DTV (not warping) is the primary cause. As the disc rotates, varying thickness creates pulsating brake force.

Typically 0.01–0.02 mm for passenger cars. Check manufacturer specification.

Use a micrometer at 6–8 equally spaced points around the disc, at the same radius.

Side-to-side wobble of the disc measured with a dial indicator. Limit typically 0.03–0.05 mm.