Brake disc thickness variation is the result of lateral runout in the face of the brake disc.Checked 2026-08-12
Brake rotor thickness variation (DTV)
Uneven rotor thickness around the disc, felt as a pulsing brake pedal.
Also called: DTV · disc thickness variation · warped rotors · brake judder
What it means
Definition
A rotor with thickness variation is thicker at some points around its face than others. Bosch describes the effect: considerable variation of the friction ring's thickness generates immediate vibrations which cause brake judder and noise. BMW's service bulletin gives the mechanism it works from — brake disc thickness variation is the result of lateral runout in the face of the brake disc, where a disc running out of true contacts the pad once per revolution and wears a thin spot.
Why a buyer cares
What it changes
The popular explanation is that heat warps the disc. BMW's own documentation describes runout wearing a thin spot instead, which is a different diagnosis and a different fix.
In practice
Where you meet it
Felt as a pulsing pedal under braking, and written on estimates as judder, pulsation or rotor resurfacing.
Two things that look alike
Not the same as
Warped rotors, the common phrase, asserts a cause the sources here do not.
Read next
Related terms
Where it shows up
Related problem files
Where this comes from
Sources
Considerable variation of the friction ring's thickness generates immediate vibrations (oscillating brake torque) which cause brake judder and noise.Checked 2026-08-12
BMW's causal claim is BMW's, for its own vehicles. Attribute it; do not state it as the general cause. The Bosch catalogue is a regional (India) edition of the maker's own document.