
Originally Posted by
Paul D
As stated, sounds like a warped disk.
You could also put the wheel on a front paddock stand, and spin it. You might see some lateral movement of the disk, but if not you need a surface guage to measure how flat the disk is when spun.
Having said that, I once read a Girling brake experts report on warped disk. He claimed in several decades of car disk assessment he'd never seen a warped disk. On every occasion the disk was flat, but what happens is driver (or rider) brakes heavy, disks get very hot, then driver (rider) leaves brakes depressed. This causes pad material to burn onto the disk in one spot. If that happens the only way to get the material off is to grind it off... Which would ruin a bike disk.