The excuse of driving through a puddle warping rotors sounds like a crock to me. Presuming that you're actually *DRIVING*, the rotors would be turning, and would get equal coverage.

Also, unless the C70's rear brakes are different from all the other 850/x70 series rear brikes, the parking brake doesn't operate the pads, but rather uses shoes that press against the inside of the rotor. This design eliminates the issue of the parking brake causing warpage by increasing cooling in the area clamped by the pads.

I'd say it's more probably that maybe you've got an area of your rotor and your pad that's glazed. This can often feel like warpage b/c the glazed area doesn't have as much friction as the unglazed areas. Try pulling stuff apart and scuffing the rotor surface by hand with a 3M green plastic scuff pad (available in supermarkets and hardware stores worldwide). Use the same thing on your pad surfaces. Spray everything down with brake cleaner (non-chlorinated, please--I like ozone layer) and reassemble. Shouldn't take more than an hour to do both sides.

-cj