I was once taught that warping is caused if one or more bobbins seizes - trapping the disk so it cannot expand uniformly. Not sure if it is true (or still true) but i religiously shake the disks loose on all bikes i have had Maybe it just satisfies the gods of braking??
Interesting. The discs will expand diameter ('out' of their bobbins) when warmed by braking, so should float better. I guess that cruddy bobbins could prevent good seating when the discs cool back to size, thus causing distortion...
I have used the m6 bolt and nut set up to spin and clean each of the bobbins, a few were tight so it will be interesting to see if it makes a difference. It would have probably made more sense to put a dial gauge to clock the discs first.
Not familiar with S drive at all, will they put an end to the problem or end to cleaning using a bolt?
Both, they cannot be rotated but EBC say they don't need to be. Have a set on my Suzuki GSX1400 and they work fine, had no problems so far.