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Old 03-01-08, 03:00 PM   #1
elbows
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Stuck cantilever brake

I have an tandem with Dia-Compe cantilever brakes -- the type where spring tension is adjustable with a cone wrench. Only one arm of each pair has this adjusting mechanism -- the other arm adjusts by setting the end of the spring in one of three slots on the tab brazed on to the frame.

Recently, after riding in some wintry weather and then leaving the bike to sit for a few weeks, both the front and rear brakes seized up completely. I could barely move the brake arms with my hands, and needless to say they wouldn't spring back after I applied the brakes. However, only the arms that adjust with a cone wrench seized up.

I tried removing the brakes, cleaning and lubing, and putting them back together, but still no luck. Either the bolt is too loose and the tension adjuster moves around, or it's too tight and the whole arm gets stuck.

I'm wondering if I put the brake back together wrong, but it there seems to only be one way to assemble it. There are four parts: the arm itself, the spring, a little plastic bit that fits around the spring, and the metal piece that adjusts the spring tension.



First I set the spring into the arm:



Then I set the black plastic bit over the spring:



Then I put the metal adjusting piece on, fitting the slot onto the end of the spring that's sticking out:



And finally I bolted the whole thing into the cantilever boss on the frame.

Am I missing something here?

Last edited by elbows; 03-01-08 at 03:08 PM. Reason: Added images
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Old 03-01-08, 04:12 PM   #2
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I've been looking for an exploded diagram for that brake, but can't find one. I suspect that you may have the springs reversed.

Sheldon has a general adjustment guide that may help.
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Old 03-01-08, 05:54 PM   #3
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look to see if the "legs" of the spring are the same length....I'm guessing that the longer leg is protruding through the adjustment nut and binding against the frame after you tighten it down.
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Old 03-02-08, 06:16 AM   #4
elbows
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I've tried the springs both ways. The legs appear to be the same length, and they don't stick out through the adjustment nut.

However, I think I've figured it out. If you look closely in the first picture you can see that there's a little metal sleeve inside the hole in the brake arm. It's stuck there, but I think it's supposed to come out.

I believe that when I tighten down the brake bolt, it should basically clamp the sleeve in place. The other end of the sleeve presses the adjustment nut against the frame, so that can't turn either. Then the sleeve acts like a bearing, allowing the arm to turn.

The other arms, without the adjustment nut, don't have a separate sleeve. They fit directly against the cantilever studs.

Now the only problem is how to get the sleeves out.
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