Mountain Bike Reviews Forum banner
1 - 3 of 3 Posts

·
Still learning
Joined
·
876 Posts
Discussion Starter · #1 ·
I've been running XTR brakes front and rear for about 6 months. In general great, but I've noticed a few issues with break wear.

1. Due to the rear caliper not being perfectly centered, when the lever is depressed and the pads pushed together, the left side (which is only barely not touching the pad, so there's no rub) first pushes the rotor, before eventually the right pad makes contact, only after which time braking starts. Somehow this has meant the right pad has worn most of the way down, but the left pad barely has anything taken out of it (would have thought more would have been taken off the left pad, since it's applying more pressure).
Placing a shim between the frame and caliper would only push the pad further in towards the rotor, causing it to rub, so doing that won't help, and the caliper is already as close to the frame as it can be, so there's no way to move the actual caliper.

2. The right pad also seems to be at a very slight angle, meaning that the lower half of the pad is worn more than the top, and the pad generally worn at an angle that's not parallel to the back plate of the pad. This is probably caused by #1 though, since the rotor is being pushed in (at an angle) before having sufficient pressure to bite.

The only thing I can think of is if there were some kind of adjustment screw to change the position of the pads/pistons, but I've looked at both the exploded view and technical docs, and can't see either.

Ideas?
 

·
Registered
Joined
·
6,762 Posts
First things first....

the caliper and thus the pads being at a slight angle in relation to the rotor indicate one thing, the mounting tabs on the frame are not symetrical. In other words one is slightly thicker than the other. This can be a bit of excess paint or a little extra metal on one of the tabs. Either way I would recommend that you have your rear tabs faced. Facing is a process where both tabs are filed down slightly and evened out in relation to one another. This requires a special tool to get it right. When done properly you end up with the mounting surfaces of the tabs flat, smooth, and concentric to one another and on the same plane so your caliper and pads end up parallel to your rotor surface. This will also likely cure your adjustment problem as a bit of metal will be removed from both tab faces. From there you'll be able to use the appropriate shims to properly center the caliper. Any competent LBS should be able to do this for you. It's not hard but it MUST be done with the proper tool, something like a Park Tool DT 1 Disc Mount Facing tool. This tool ensures that the tabs end up properly oriented to one another and that they are also porperly oriented to your drop outs as well. Something that can't be done by hand with a simple file or the like. Also I am assuming that you have checked that your hub is properly seated in the drop outs as well. I would say so because if not you'd be having bigger problems than this. :thumbsup:

Good Dirt
 

·
Still learning
Joined
·
876 Posts
Discussion Starter · #3 ·
Yeah, actually the wheel/disc can change position ever so slightly depending on how you insert it into the drops, but ultimately it still 'works'.

I'll have my sponsor/LBS look at the tabs - thanks for that. There's a few things I don't want to have anything to do with risking screwing up myself - servicing forks, building wheels, and facing tabs.
 
1 - 3 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top