When cars sit for a while, rust can build up on the rotors and around where the pads are. Usually a few hard braking attempts will get rid of the surface rust.

The only way I could think of that they would warp while sitting would be if you have a stuck piston in a caliper that is applying constant pressure to one side of a rotor...that theoretically could push it out of true.

You could always take the rotors into a shop and have them refinished..

Nate
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1997 850, 1979 242GT, 1990 740GL

Sarah:

Ken C is correct, the rotors have rusted. This happens on my eclipse often as I drive it infrequently (insert here: "Time to sell eclipse"). Typically, the rust goes away/gets rubbed off after 20 or so miles of city driving. In effect, the pads wind up resurfacing the rotor through friction.

jorrell
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92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!

Your rotors didn't warp overnight -- they rusted. You probably had some humid weather, and rust formed on the rotor surfaces, and especially under the pads. Probably, you'll see pronounced rust spots not only over the rotor surface but especially pronounced blotches matching the outline shape of your brake pads.

Those rust spots -- not the uniform rust, but the more rusted spots that formed under the pads -- really give the feeling of a warped rotor.

This happens often, especially in my rainy part of the country. The only solution that I've found for this on a car that's used infrequently is to get rotors that are cadmium plated -- I've found that it helps a lot (although it's not a perfect solution, especially after a time when the cadmium plating eventually wears away).