The vibration from the warped rotor is not perceptible until the brake pedal is depressed forcing the pistons and pads outwards against the rotor. With no pressure on the brakes the pistons and pads follow the rotor by shifting from side to side as the warped part of the disc rotates through the caliper. The fluid behind one piston is pushed backwards by the warp (along with the piston and pad) and the fluid behind them flows to the piston in the opposite side of the caliper pushing that piston and pad outwards. The brakes in effect float back and forth with the warp.
Below are diagrams showing the warped disc with the warped portion of the disc at the top of its rotation (left) and with the warped portion of the disc passing through the caliper (right). Below that is an animation from the hydraulic portion again showing the fluid moving back & forth behind the piston and pads (left) and an animation of the pads, caliper, and rotor (right).
