Sun Dec 06, 2020 1:17 pm
As you have received no responses, I'll state my opinion based upon experience.
The pads, being circular, tend to rotate, particuarly on the static side with it's central adjuster, which also means that it is pivotal with a low area of contact.
Copaslip is great stuff, but on the pad sides will encourage rotation.
TBH my road SX has a similar set-up to yours but I only lube the pads on their bases, & use sintered pads that I select to be a good fit. Fortunately, my brakes do not squeel, but if they did, I would introduce something to stop the rotation.
Within racing, prior to outboard discs becoming the norm, some riders used to go to the extremes of selecting pads with a small tab & notch a corresponding location slot in the backplate. Of course, if you were to notch the pads & fit a dowel 'half & half' to the backplate on both sides, this would achieve the same objective.
The other thing that the likes of LLRT did was to dispense with the adjuster & fit a shim beneath the static pad, effectively a large washer. Ha! In alloy for the weight saving!
We've been here before, but my preference is not to modify the disc itself & retain the anti-rattle circlip. If the disc is cleaned up meticulously on the bore & pin holes, along with the pins & disc spigot it will not bind up & will run truer. My belief is that the disc can flutter a tad & encourage the tendency to squeel.
If you could @ least refit the anti-rattle circlip (nicely Copasliped) then that too should help.