Originally Posted by
SDHawk
Hi, newbie to disc brakes. Just got a 2003 bike with Shimano XTR discs (BR-M965). The front wheel calipers are not centered and rub very slightly on the inside caliper. It's consistently off-center through the entire rotation. The rotor seems straight and tight and the wheel is true. These brakes have the "post" mounting thing, where the mounting bolts are perpendicular to the rotor (see pictures). So it doesn't seem possible to adjust in/out with those bolts? I found a manual online here, but it's way over my head:
https://hollandbikeshop.com/images/SI-8CM0G-000-ENG.pdf
Any advice would be much appreciated, thanks.
That manual shows that the calipers are centered using .5mm and .2mm shims under the mounting bolt.
However, this is not a new set up, so it is more likely you are having a problem of the pistons no longer moving symmetrically. Grab the lever and watch the pistons - do they move at the same time? Do they move the same distance?
If not, the pistons should be cleaned and lubed. If that isn't sufficient, I have had great success getting the slow piston to move by holding the more active piston while I pull the lever. A couple of those in and out gets the late moving piston freed up.
Don't just shim the pads. You'll find that the off center condition just gets worse as the one side gets stickier.