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Old 01-13-10, 11:22 PM   #1
danec99
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Dual Pivot Brakes - only one side pivots

Changing title to Side Pull Brakes - Only one side works

HI
I have an '89 Trek 1200 with Shimano 105 dual pivot brakes. When i squeeze the lever only the right brake pivot moves, the left does nothing. You can squeeze the pivots and both move fine, so it must be the connection. I looked around but didn't find the answers I needed, so...If someone could point me in the right direction I would appreciate it. BTW the bike is new to me, so I figured I might have to replace the cables, what is a good source for this information. Thanks.

Last edited by danec99; 01-14-10 at 11:12 AM. Reason: A noob mistake in part ID
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Old 01-13-10, 11:27 PM   #2
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HI
I have an '89 Trek 1200 with Shimano 105 dual pivot brakes. When i squeeze the lever only the right brake pivot moves, the left does nothing. You can squeeze the pivots and both move fine, so it must be the connection. I looked around but didn't find the answers I needed, so...If someone could point me in the right direction I would appreciate it. BTW the bike is new to me, so I figured I might have to replace the cables, what is a good source for this information. Thanks.
They should both spring back when compressed towards the rim, disconnect the cable and do this manually. If it's the cable it'll be immediately obvious. If the brakes need to be overhauled, it's fairly simple.

http://www.parktool.com/repair/readhowto.asp?id=20
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Old 01-13-10, 11:34 PM   #3
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When I squeeze the front brake the cable housing goes down with it, when I squeeze the rear brake the pivot moves down but the cable housing remains in place, separating from the brake mechanism. How does the cable housing attach to the caliper?
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Old 01-13-10, 11:40 PM   #4
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When I squeeze the front brake the cable housing goes down with it, when I squeeze the rear brake the pivot moves down but the cable housing remains in place, separating from the brake mechanism. How does the cable housing attach to the caliper?
The cable is secured to the caliper via a 5 mm hex bolt. If you trace the housing to where it stops into the brake and then follow the cable it'll be immediately obvious.
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Old 01-14-10, 02:20 AM   #5
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I am having a hard time wrapping my head around this without a dual pivot brake in front of me, but i am just going to say that if when you pull on your brake lever and the cable housing separates from the barrel adjuster where it attaches to the caliper something that is supposed to be moving is not. I feel like it might be an issue of your cable being suck somehow to the housing, be it by kinking, bent housing end, corrosion, whatever. disconnect the cable from the 5 mm hex bolt Operator mentioned and check to make sure the cable moves freely through the housing with very little friction and the housing not moving at all.
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Old 01-14-10, 02:40 AM   #6
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My bet is the 'cable separating from the barrel adjuster" is a red herring. It just means the ferrule is not rusted to the barrel adjuster.

Now, on your dual pivot brakes there should be a little adjustment screw on top.



Your problem sounds like this screw adjustment is way out of whack. Of course it is harder to tell for sure from your description than from being able to look at the brake. But on a dual pivot brake that screw is what makes the left arm move in sync with the right arm.
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Old 01-14-10, 04:27 AM   #7
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On these brakes the housing needs to have enough play or slack that it can follow the arm when you apply the brakes. If the housing is clamped badly or isn't long enough it won't have the slack needed to move with the arm.

The other possible cause is that the whole caliper is jammed over to one side. The adjustment screw can only do so much. The caliper needs to be twisted in the mount until the arms are operating within the acceptable range of the springs that do the return action. The centering screw only being for the final small adjustment to find tune the equal travel of the arms.
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Old 01-14-10, 09:45 AM   #8
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i had this problem with my rear brake when i clamped the housing to the top tube, too close to the brake arm. not enough slack to allow the brake arm to pivot as bcrider said.
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Old 01-14-10, 11:07 AM   #9
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*UPDATE*
I am learning, little by little. These are SIDE PULL BRAKES. Which might explain the missing centering adjust screw. So...

Only the right side engages, the left side sits. Is the adjust supposed to hold the end of the cable/housing securely? This pulls out to reveal cable as I squeeze the calipers. With this new information the Park website concerning Side Pull Brakes seems relevant. But any advice is greatly appreciated.
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Old 01-14-10, 01:38 PM   #10
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If you're squeezing the pads together by hand then the housing coming up out of the adjuster is perfectly OK. You're slackening the cable after all and something has to give. In other cases where there's a long run of open cable it's normal for that area to bulge loose. In your case the housing is coming up. No biggie either way. At most it just means that the housing end thimble isn't distorted.

The ones in the picture above showing the adjustment screw are side pull brakes as well. But they are dual pivot side pull brakes. It sounds like you may have single pivot brakes. So if only one side is moving we go back to my previous post that mentioned that you need to center the caliper by pivoting it on the mounting bolt. There is only one spring that forces both arms out at the same time with no adjustment to even them up. Twisting the entire caliper side to side IS that centering adjustment. But because both arms need to be able to move freely if your housing does not have enough slack to bend freely it can prevent this arm float from happening.

The other option is that the pivot may be rusted and the one side is jammed tight. But it would have to be REALLY bad to appear to be jammed solid.
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Old 01-14-10, 11:43 PM   #11
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Originally Posted by BCRider View Post
The ones in the picture above showing the adjustment screw are side pull brakes as well. But they are dual pivot side pull brakes. It sounds like you may have single pivot brakes. So if only one side is moving we go back to my previous post that mentioned that you need to center the caliper by pivoting it on the mounting bolt. There is only one spring that forces both arms out at the same time with no adjustment to even them up. Twisting the entire caliper side to side IS that centering adjustment. But because both arms need to be able to move freely if your housing does not have enough slack to bend freely it can prevent this arm float from happening. .
Getting single-pivot sidepull calipers to be centered and to stay centered is a little bit of an art form. This Park page has some techniques and tips: http://parktool.com/repair/readhowto.asp?id=22 . As long as neither side rubs you should be OK since the brake will squeeze the rim evenly once both pads contact the rim.
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Old 01-15-10, 12:56 AM   #12
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You're right on that Jeff. Mostly because shifting the entire caliper is so crude compared to using an adjustment screw.
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