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Old 02-01-12, 05:48 PM   #1
idoru2005
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Excessive friction in rear brake housing or weak caliper spring?

I'm having issues with my rear brake. The brake caliper is a Tektro (unsure of model) which came standard on my 2008 Specialized Allez. The brake cables are relatively new (less than 1 year old), and in good condition. The brake cable housing at the rear (where the cable enters the caliper) is several years old.

The problem is the caliper doesn't fully open after I release the brake lever. The brake partly releases, but not completely, such that one pad slightly rubs the rim. If I tap the caliper or help the cable move within the housing, the brake will fully release.

Yesterday,I removed the caliper and gave it a good cleaning. I also pulled the cable out of the housing and gave it a good cleaning and inspection. The cable is in new condition.

After re-installing, I still have the problem where the brake slightly "stick" without fully releasing. It appears there's friction in the brake housing just before the caliper, or the spring has lost its springyness and can't overcome the friction in the housing.

Is it plausible that the caliper spring is getting worn out, thereby necessitating a new caliper? Or should I just change that rear brake cable housing? I'm wondering if using a longer housing (and hence smoother bends) will help alleviate this issue.

Your input is greatly appreciated.

Last edited by idoru2005; 02-01-12 at 05:51 PM. Reason: fixed some typos
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Old 02-01-12, 05:51 PM   #2
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Is the housing too long or short, kinks. Since you disconnected it from the caliper see how much resistance when you move the brake lever.
also is the caliper center bolt too tight? just another thing to check.
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Old 02-01-12, 05:58 PM   #3
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Very little to no friction through the front housing when I move the lever. I can feel slight friction in the rear housing because of the bends. I have a small frame bike (49cm) and I'm using the original rear housing that came with the bike. Front housing is relatively new since I changed my brifters (they run under the bar-tape). I'll check the caliper center bolt. Maybe it is too tight. When I was inspecting the caliper (when it was removed from the bike), after lubing it, I could tell that the movement wasn't completely smooth. In other words, I could feel that it's movement was not smooth through it's entire range. I could feel it had a slightly "jerky" movement when opening.
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Old 02-01-12, 06:08 PM   #4
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idoru2005: Springs do not wear out, look for your trouble elsewhere. Since the cable wire is in new condition I would look to the housing; worn, dirty or the ends not properly prepared. Housing is cheap, I'd suggest replacing the whole run with good-quality lined housing of the correct type. DO NOT use compressionless shift cable housing, though. Don't make the rear housing too long, it should enter the frame stop and the caliper straight.
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Old 02-01-12, 06:23 PM   #5
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isolate the brake and cables. unhook the cable to check to rear brake pivots. if it moves freely then its the cables or lever
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Old 02-01-12, 07:26 PM   #6
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Originally Posted by reptilezs View Post
unhook the cable to check to rear brake pivots. if it moves freely then its the cables or lever
+1

If the caliper moves freely with no cable attached your problem is the cable/housing or lever. Make sure the cable isn't kinked or too long/short and be especially careful it's installed correctly into the brake lever. The housing should be firmly seated which can be tricky on some levers.
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Old 02-01-12, 08:06 PM   #7
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you stated that you gave your caliper a "good cleaning", but did you disassemble it, relube it, and readjust the jam nut? it may be too tight and binding. it works (the nut, that is), if yours are like all the ones i have seen, with the same principal as the axle locknuts. should move easily but no slop, just like your hubs.
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Old 02-02-12, 01:21 PM   #8
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Originally Posted by reptilezs View Post
isolate the brake and cables. unhook the cable to check to rear brake pivots. if it moves freely then its the cables or lever
Thats the thing. See what I wrote earlier:

Quote:
When I was inspecting the caliper (when it was removed from the bike), after lubing it, I could tell that the movement wasn't completely smooth. In other words, I could feel that it's movement was not smooth through it's entire range. I could feel it had a slightly "jerky" movement when opening.
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Old 02-02-12, 01:25 PM   #9
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you stated that you gave your caliper a "good cleaning", but did you disassemble it, relube it, and readjust the jam nut? it may be too tight and binding. it works (the nut, that is), if yours are like all the ones i have seen, with the same principal as the axle locknuts. should move easily but no slop, just like your hubs.

No, I just did a cleaning without disassembling it (gave it a good flossing). I'll probably take the time to disassemble it. I guess I need a nice diagram of dual pivot calipers because I was apprehensive at first about taking the thing apart. Not sure what I know what you mean about "jam nut" but I will look into this, as well as changing that rear housing. Front housing is new. Anyway, I'll try to keep the new rear housing short as another poster suggested.
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Old 02-02-12, 04:14 PM   #10
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Originally Posted by idoru2005 View Post
No, I just did a cleaning without disassembling it (gave it a good flossing)... Not sure what I know what you mean about "jam nut" but...


pic is blurry, i know (blame polaroid), but the nut that is shaped like a cone is what i am calling a jam nut. and notice the thinner and slightly larger diameter nut right behind it. the thin nut has a washer behind it and there is a thin washer between the caliper arms too. these serve as simple bearing surfaces that need to be lubricated. anyhow, the two nuts need to be turned in opposition to create 1) a fixed endpoint for the caliper arms (the other fixed endpoint is the fork crown.) a proper distance between the fixed endpoints is defined as no slop but freely moving caliper arms.
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Old 02-02-12, 04:57 PM   #11
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Thanks hueyhoolihan,
Your picture shows a single pivot brake caliper. Mine is a dual pivot caliper very similar to this:

http://www.tektro.com/_english/01_pr...e&sort=1&fid=2

If there's a corresponding jam nut on this configuration, I'd appreciate if someone could show me how to get to it.
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Old 02-02-12, 05:07 PM   #12
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I found this:

http://www.parktool.com/blog/repair-...-brake-service
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Old 02-02-12, 05:08 PM   #13
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When I had this problem it was because the caliper was being pinched too much by the adjusting nuts on the mounting bolt. You should be able to adjust the nuts so that the brake pads stay equally spaced from the wheel rim and without pinching the caliper too much.
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Old 02-02-12, 05:09 PM   #14
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Quote:
Originally Posted by reptilezs View Post
isolate the brake and cables. unhook the cable to check to rear brake pivots. if it moves freely then its the cables or lever
+1

The key to a decent diagnosis is to separate the components so you can check each separately.

Springs don't wear out, though they could weaken if you force them beyond their limits. it doesn't sound like you did that, so I'll bet the springs are fine. The problem is friction. It could be in the pivots themselves due to dirt, dried lube, or cold lube if you're in a cold area.

Most likely it's the cable, since they go the fastest. The wires last, but the liner wears through at the inside of the bends raising the friction. It could also be thick lube in the cable (winter issue), or that the wire is fraying up near the lever, possibly causing it to hang up where it passes through the lever adjuster or ferrule.

You don't necessarily need to disconnect the cable to analyze the issue. Unhook the noodle at the quick disconnect point and work the lever against hand tension at the noodle. Also move the brake arms in slightly and take pressure off slowly to see if they move back smoothly with your hand.
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Old 02-02-12, 05:56 PM   #15
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Either reading comprehension is lax or my original post is unintelligible. I did mention that I isolated the cables, housings, and caliper. Here's what I found:

1) Cable is flawless. Regardless, I cleaned it with Simple Green, and re-lubed the entire length of cable.
2) Cable moves completely without friction in the front housing (the housing that runs underneath my bartape). This is 1 year old housing.
3) There is absolutely no friction in the brake lever. The thing moves freely.
4) There is a small amount of friction through the rear housing just before it enters the caliper. Though I would expect the spring tension to easily overcome this small amount of friction.
5) Upon removing the caliper from the bike (and detaching the cable), when squeezing the calipers with my hand, I felt very little friction. However, when releasing the calipers slowly, I could feel stickiness in its movement.
6) After I reassembled everything, I still have the problem of the brake not fully releasing.

I feel as though this "stickiness" upon release, combined with marginal amount of friction in the rear housing is keeping my rear brake from fully releasing when I release the brake lever.

I've since found a nice Shimano brake diagram and Park Tools writeup (which is pretty poorly written IMO). I will attempt to disassemble the caliper and clean/grease the pivots. Hopefully this will resolve my issue. I'll probably replace the rear brake housing since that is 4 years old now (or simply drip some lube through it).

Thanks to everyone who posted helpful comments!
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Old 02-02-12, 06:03 PM   #16
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Originally Posted by idoru2005 View Post
Either reading comprehension is lax or my original post is unintelligible.
Usually the advice around here is pretty good. Looks like you got the short end of the stick. Most brake problems are cable related, hence the smattering responses about the cable (including mine, I missed the part about the brake sticking with NO cable.)

Disassembling and re-greasing the pivots seems like the right approach. I've never had to disassemble a dual pivot brake, good luck. It doesn't look too complicated though.
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Old 02-02-12, 07:07 PM   #17
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5) Upon removing the caliper from the bike (and detaching the cable), when squeezing the calipers with my hand, I felt very little friction. However, when releasing the calipers slowly, I could feel stickiness in its movement.
This is EXACTLY why I suggested squeezing and releasing slowly. If the pivots were friction free the springs would open the brake smoothly at any speed. You can remove the pivot bolts and slide the arms off the posts then clean and oil (or grease with a very light grease) the pivots, and /or bushings. Different brakes are built differently, so if you're not the kind of person good at figuring things out find and read a tutorial specific to your brakes. If you decide to go ahead and just take them apart, work carefully, and lay the parts out on a paper towel maintaining the sequence and orientation.

If you're not ready to take them apart, you can take a shortcut that works about half the time. Drip something like typical homebrew chain oil (mid weight oil, thinned with naphtha or mineral spirits) to the pivot area both in front of and behind each arm. Give it a minute or two to penetrate then work the arms and see if that frees things. When you're done, you'll likely have to recenter the brake via the spring tension screws (or cam, or whatever).
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