I have heard that there is another cause of uneven braking that happens when the pads are applied to the disk when stopped and hot. I think it was something to do with material from the pad being deposited on the disk and building up an area of increased friction - not actually warping the disk. Sam cause and effect, but by a different mechanism.
Repeated disk warping could also be caused by run-out somewhere else in the hub. If the hub's not quite running true, there is crud on the surface which is preventing the disk seating or possibly even if the wheel is a little out-of-round it could cause premature disk failure.
It'd be worth getting out a DTI and measuring the disks to see if it's just one that has warped, and to check that the new ones are running perfectly true when replacing.
Kevin
Kevin
Yes, there post a post here a while ago with a link to someone's website who says that being a race mechanic for many years (in the U.S.) he has never seen ‘warped’ discs, instead as you say the vibration is caused by uneven material transfer from the pads to the disc surface due to overheating. But even so, he also says that this problem rarely occurs with road-going cars, and is mainly confined to race tracks.
The other point you raise is very interesting. The previous set of discs became 'warped' shortly after the front wheel bearings became loose and needed replacing, so it could be that the play on the front bearings is what caused the ‘warping’ of the previous set.
But I replaced the front wheel bearings at the same time when I did the discs, so now have two new bearings... they may have gone again, in which case I will have to investigate why (and also keeping in mind that the front bearing went at 50k first time 'round, which is unusual as they should normally last double that mileage, and also both went at the same time...).
I did not yet re-check the front wheels for play, but will do so soon to see if the front bearings are loose again. If they are then this will explain the discs becoming 'warped' again, though I will still have to figure out why the bearings go... if there is no play at the front wheels, then I am back to square one on the ‘warped’ discs issue.