Originally Posted by Subzero2003
First of all, discs very very rarely warp, and almost never do through road use. When people diagnose "warped discs" what they almost always mean is "friction material from the pad has transferred to the disc, meaning that the disc is very slightly not flat". Automatics are particularly susceptible to this as if you come off a motorway onto a slip road - you may have just braked fairly hard from 90mph down to 0mph. This heats the pad massively and then when you are sitting at the traffic lights with your brakes applied, this transfers the pad material slightly to the disc.
Just to confirm, when the various garages have changed the discs, the problem has gone away completely for a few months?
Correct and the most likely cause. The garages that have replaced the older discs have don't it for 2 reasons, to line their own pockets or they have no understanding of pad transfers effect on the wobble under braking.
Fix - Brake from 80 to 30 hard 3 times and then drive without using the brakes for a bit - a motorway at night and then you will be fine, unless the discs have a lot of pad transfer build up.