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It is common on any car, it may be warping [either permanently warped or only warps whilst hot] or it may be due to the cooling gradient of the casting [nearly all ventilated discs are cast vertically] if the was a significant difference in mould temperature from top to bottom the the graphite structure changes significantly altering the friction coefficient of the rotor causing a pulsing that feels like a warp.

If it is a cold - permanent warp this can be trued up without even removing the disc, some good garages have a turning attachement that goes where the calliper would be then drive the hub and take off sufficient material - this process trues the disc to the hub [more accurate than new if you think about it] but if your discs are close to the minimum it is a fools errand to do anything but change them, and beware of cheap discs, our cars are to heavy and powerful to get away with them.
 

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Rule of thumb about warped rotors:
If you feel thumping in the steering wheel it is the front rotors.
If you feel it more in the body it is the rears.
 

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Take it to a good brake shop and have them measure the following

- thickness of rotor
- run out using dial indicator

This should isolate the rotors which are causing the problem. If the thickness of the rotor is close to the limit don't machine it. Get it replaced since it will likely warp again.
 
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