Question

a vibration or pulsation in the brake pedal when the brakes are applied is usually caused by
select one:
a. warped rotors runout
b. oil or grease on the linings
c. frozen or sticking calipers
d. brake hose collapsed on the inside

Explanation:

When brake rotors are warped (have runout), as the brake pads clamp onto the uneven rotor surface during braking, it causes vibrations or pulsations that are felt through the brake pedal. Oil or grease on linings would more likely cause reduced braking effectiveness rather than pedal vibration. Frozen or sticking calipers might lead to uneven braking force distribution but not the specific vibration/pulsation described here. A collapsed brake hose inside would cause issues like reduced brake fluid flow and soft pedal feel rather than vibration/pulsation.

Answer:

a. warped rotors [runout]