Disc Thickness Variation, DTV is a variation in thickness of the disc rotor braking surfaces as it rotates on the axle. The hydraulic pressure behind the caliper pistons force the brake pad to maintain consistent load on the rotor surface. When the thickness of the disc rotor varies by as little as 20 microns, the pads oscillate back and forth causing a pulsation in the hydraulic circuit back to the brake pedal.
This brake pad osculation also causes a variation in brake torque as the brake pads grab and release over the higher portion of the rotorr thickness. This its typically noticed in the steering wheel as the brake torque from the left and right axles is different and out of sequence.
Brake pad material deposits are often mistaken for DTV.
The key differences to be observed are:
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