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Old 04-26-07, 11:08 PM   #1
ApolloCVermouth
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Single pivot brake issues...

I'm running nashar bulhorns, nashbar bar-end levers, and an old shimano 600 single pivot road brake as a front brake on my fixed gear. It won't spring back on its own anymore. The cable isn't that old. Ideally I would just buy a new dual pivot brake but this isn't an option at the moment. Part of the problem may be that the brake was designed for old style road brakes and that routing the cable along the inside of the bullhorn just produces too much friction. Maybe there is a better way of routing the cable. I have noticed that the brake stiffens up after it rains and some chain lube makes things better for a while. My question is this: Can I clean and rebuild this brake? What are the options I should try to get this brake to work properly? Thanks.
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Old 04-27-07, 02:49 AM   #2
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Can you describe the problem in more detail?
Does one pad remain against the rim as you release the lever?
Have you tried stressing the spring/replacing it?
Did you lube the spring, pivots, cable?

The cable routing you describe should not affect brake function.
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Old 04-27-07, 02:51 AM   #3
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Did you check to see if the brake springs aren't broken? Springs do get soft and loose some of their spring, for lack of a better term, over time. I'm not really sure if a dual pivot will help. You might want to take everything apart and do a thorough clean and lube. Good luck

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Old 04-27-07, 06:29 AM   #4
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When you clean and lube, which you should, pull the two arms of the spring further apart. This will make the action of the spring more pronounced. Do the Nashbar levers have returns springs in them? If not, a set of levers with springs will help with lever return and more positive action.
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Old 04-27-07, 07:55 AM   #5
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Quote:
Originally Posted by ApolloCVermouth
My question is this: Can I clean and rebuild this brake? What are the options I should try to get this brake to work properly? Thanks.
Yes you can! They're very simple to take completely apart, and you can then clean all the parts and reassemble. This may not be necessary though, if you just use the end nut to reduce the pressure being exerted on the arms, pinching them against each other at the pivot point. You want just enough pressure so there is no front-to-back play (when you grasp the brake pads, and move them front-to-back in opposite directions, you don't want to feel looseness or play). But if there's too much pressure, the arms can't move freely and they bind up, like yours are doing. Those old 600 single-pivots are very nice brakes, and the springs very seldom get too weak to function. I'd sure try the lube and adjust procedure, and if that doesn't work, take it apart and clean it thoroughly and try again, before giving up on it. Here's a link to the ParkTool description of this adjustment that I described (illustrations may help). Scroll down to below half way, to where it says "Sidepull Caliper Arm Adjustment".
http://parktool.com/repair/readhowto.asp?id=22
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Old 04-27-07, 08:19 AM   #6
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Single pivot brakes are EASY to service.

Once you get it off the bike, use a pair of pliers to release the spring, then take off the two nuts on the pivot (retainer nut and capped lock nut) and notice how things come apart. clean real well, and lube as you put it together. I use Triflow lube when I am assembling my brakes, and so far it does well. I don't ride in the rain, if I did I would probably use grease.

I also remove the pads when doing the cleaning, lubing and assembly just to keep from accidentally lubing the pads.

For the tension on the pivot nut during assembly, I tighten until it starts to bind, then back off very slightly (about 1/8 turn) then put on the lock nut. It may take a couple of tries to get free motion along with minimum flex. If you are too tight it binds, if you are too loose, you get excessive flex. You can detect the flex by taking an arm of the caliper in each hand, and applying a little twisting pressure. Play with it until you get free motion with a minimum of movement. (as the previous poster suggested... the same process works on or off the bike).

Of course, with all this said... your first check should be to remove the cable and see if the brake binds. If not, then whether the cables are fairly new or not, there might be an issue related to the cable... look for burs at the ends where the housing was cut, or places where the cable may have been folded which caused a crimp.
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Old 04-27-07, 08:20 AM   #7
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Originally Posted by lawkd
Yes you can! They're very simple to take completely apart, and you can then clean all the parts and reassemble. This may not be necessary though, if you just use the end nut to reduce the pressure being exerted on the arms, pinching them against each other at the pivot point. You want just enough pressure so there is no front-to-back play (when you grasp the brake pads, and move them front-to-back in opposite directions, you don't want to feel looseness or play). But if there's too much pressure, the arms can't move freely and they bind up, like yours are doing. Those old 600 single-pivots are very nice brakes, and the springs very seldom get too weak to function. I'd sure try the lube and adjust procedure, and if that doesn't work, take it apart and clean it thoroughly and try again, before giving up on it. Here's a link to the ParkTool description of this adjustment that I described (illustrations may help). Scroll down to below half way, to where it says "Sidepull Caliper Arm Adjustment".
http://parktool.com/repair/readhowto.asp?id=22
+1.....lawkd has great advice here, definitely try the simplest thing first: try loosening the nut just a bit and see if it doesn't free up the spring action of the brake-
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Old 04-27-07, 08:46 AM   #8
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older sidepull brakes like this Shimano 600 model (probably what you have?) actually have stronger return springs because they were designed to use with levers that don't have their own return springs.

I doubt the problem is cable friction if you've taken good care of them - newer cable lined cable housing is smoother than what was available at the time these brakes were produced, anyway.

If the spring is broken, new brakes would help. Dual-pivots don't have stronger return springs.

But the advice of the last three posters is all good - you should service the brake, make sure that the pivot is clean and not too tight.
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Old 04-27-07, 10:44 AM   #9
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Originally Posted by ApolloCVermouth
The cable isn't that old.
How about the cable housing?
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Old 04-27-07, 11:18 PM   #10
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Thanks for all the advice. I've backed off the nut in front and the brake itself springs back well enough. I do think the problem is with the cable or housing. I will re-cable the brake paying more attentiong to getting as smoth a transition as possible. I may even run the cable out of the bar earlier rather than having it come out around near the stem.
The bike has been out in the rain and that may have something to do with it. It's pretty damp here in Halifax.
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