Bicycle Mechanics - Deore XT BR-M750 brake install mystery!

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mattkime
06-20-08, 05:01 PM
I've had this rear brake for about a year and its never quite fit right. I recently managed to lose a pad and bought kool-stops which take up a *little* bit more space so I'm re-examining it again.

I can place the brake in the top spring hole but then the brake pad holder isn't parallel. The socket-nut (is that a good name for it?) does allow it to be mounted at an angle but this is a bit too severe.

http://img255.imageshack.us/img255/2718/img0531yi6.jpg

I can place it in the middle spring hole and then the brake pad holder is _perfectly_ parallel to the rim - but now there's no tension pushing it away from the rim. The Spring Tension adjustment screw seems like it could fix the problem - if it were twice as long as it is.

http://img440.imageshack.us/img440/1641/img0537id8.jpg

In both pics I'm holding the lever at the point where the spring starts to push back.

I've wondered if there is something wrong with the mounts for the brakes. Still, I've stared at this as hard as i can - this is the best info i could come up with.

Has anyone come across this problem before? And found a solution?

well biked
06-20-08, 09:27 PM
Try this: with the brake mounted with the pin in the middle hole, take the return spring loose and bend it to give the spring more "spring." Hopefully when you put the spring back in place, it will then have enough power to pull the brake arm away from the rim like it's supposed to-
the_mac
06-20-08, 11:09 PM
The top pic is just fine. Having the spring bringing it back that far is okay, you're going to rely on cable tension to bring the arm parallel to the circle of the rim. Just leave it mounted in the top spring hole and then go ahead and set the cable tension for correct distance on the pads and for parallel brake arms, then adjust centering by bending the springs or using the screws.

mattkime
06-21-08, 12:01 AM
>>you're going to rely on cable tension to bring the arm parallel to the circle of the rim.

thats part of the problem - it _doesn't_ become parallel with the rim. it only moves parallel to the position i've shown.

anyway, i'll try the above advice provided by well biked. still, i don't think i should need to bend parts to get them to work properly. (maybe i'm weird?)