67tony 

I disassembled and cleaned these Shimano BR-AT50 brakes, and upon reassembly have a slight problem. It seems that one spring is stronger than the other, so that when the brakes retract only one retreats from the rim. The rear is fine, the front is the problem.

One spring is gold in color and the other silver...I don't know what material they are. Thinking of matching materials and swapping one from the rear I find out they are side specific, not matching, so that would not work.

Is there anything I can do about this? Are these springs available anywhere?

bradtx

Usually there are three holes in the cantilever post to adjust the spring pressure. Tinker with these to align the calipers properly.

Brad

Fred Smedley

Should also be a little allen screw also on one of the lower arms , at least on the XT 732 I just installed.

zukahn1 

I would also double check your assemble it is pretty easy on some of these to put the sping in backwards or upside down. Also did you keep all of the parts from each side seperate when you took them apart as they may be right or left specific and the parts from a deferent lever assemble don't always match up even when there the same.

67tony 

Thanks for the ideas.
On these (maybe they are a basic model?) there is no allen, and only one hole choice on the post. Parts are very simple; plastic piece, spring, brake, washer, and the bolt. The only possibility left, it seems, is if the spring has a certain fore/aft positioning.

The Golden Boy 

As Brad mentioned, there's often different holes for spring tension. Also, the gold spring goes on one side, and the silver on the other. You can check to see on the other set if the gold goes on the left or right.

blilrat

If you know the springs are correct, then I would check the studs. These brakes are extremely sensitive to any issues with the studs. I always LIGHTLY sand with very fine sandpaper or use an emory cloth to clean off any rust or grease build up and then grease liberally.

Standalone 

Yes, gunk on the studs might be the issue. Taking apart and re-assembling wonky old cantis is indeed an education. I learned a lot trying to cobble old cantis together to fit on an old 620 frame.

I like the way those BR-AT50 brakes look.

67tony 

Just one hole on the mounting stud. Posts are clean and greased. I flipped the weaker spring (right side, facing brake, silver one) to no avail. I'm supposing that the different material weakens over time?

Standalone 

Bike shops have buckets of those springs. Why not drop by and ask for a few the match yours to see if you get different performance?

The Golden Boy 

Very much like the BR MC-70 XT brakes.

67tony 

Ha...great minds think alike. I just did that this morning, and came away with two possibilities. I went to a very cool shop in Portsmouth called Cycle Classics, owned by Gordon Freedman.

noglider 

Disengage the springs and make sure there is no friction on either side. If you find they both spin equally well, then you can weaken one spring or strengthen the other by winding it in the appropriate direction. You may even want to do both (weaken one and strengthen the other).

67tony 

I tried strengthening the weak spring, but did not want to "unwind" it too much for fear of creating too much diameter.

However, I had good success at the bike shop. One of the springs they gave me had an ever-so-slightly thicker wire, yet was the same diameter as my original. Voila...equal retreat from the rim for both pads!

Thanks for all the tips and suggestions!

bradtx

Sorry for the misinformation regarding the number of spring locating holes, I've never seen one with a singular hole. The bike looks like an excellent rando platform.

Brad