Disc Brake question

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Disc Brake question

Postby greenfast » Sun Mar 14, 2010 11:00 am

Since this is my first bike with disc brakes I am not to familiar with working on them, thought others on here might have some insight. What I am getting is one spot on my rear brake the rotor seems to be warped as you can hear it rubbing the brake pad, but visually inspecting it doesn't show this. Is there any way to check to make sure it is or isn't warped? Any help is appreciated.
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Re: Disc Brake question

Postby Jaxon » Sun Mar 14, 2010 11:32 am

That is the one thing that really bugs me about disc brakes.

There are a few ways correct it, some free, some not. One is to spin the wheel and figure our where it rubs. Then bend the rotor slightly by hand, with a tool of your choice, or with the proper tool like this:

http://www.parktool.com/products/detail ... &item=DT-2

The professional way is with a wheel truing stand and a rotor truing attachment such as:

http://www.parktool.com/products/detail ... &item=DT-3
http://www.parktool.com/products/detail ... em=DT%2D3i

If you have brake calipers that can be moved laterally with one or more bolts, you can loosen the bolt, spin the wheel so the rotor centers the brake pads, then hold it in place and tighten the bolt. That worked perfectly on one of my old bikes that I couldn't get rid of the noise by bending the rotor. If your calipers are shimmed, you have the nightmare of trial-and-error to adjust the spacing to center them.

It's really annoying when you think you've fixed the noise, and then it comes back after you've been riding for a while.
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Re: Disc Brake question

Postby Rage » Sun Mar 14, 2010 11:36 am

That's typical of disk brakes and no big deal if it's not excessive, and this doesn't sound like it is. Easy fix, just takes a little patience, like truing wheels. And similar to truing wheels, you can either use a truing stand or just leave it on the bike and let the brake rub guide your adjustments. All you need to do is find where the rub is, and bend the rotor away from the pad. I now use the Park DT-2 Tool, but used to use a cresent wrench with success (make sure you clean any grease off of the jaws!). Sometimes I'll put a dial indicator on the truing stand, but usually not. I think using the brake rub indication with the wheel on the bike works well enough. YMMV.

http://www.parktool.com/products/detail ... &item=DT-2
http://www.parktool.com/repair/readhowto.asp?id=125

Sounds like it's time for a bike-night!
Rg.

[Edit] - Hah! Jaxon beat me to it. Brings up a good point about calipers though: Avid's CPS mounting are much easier to position than calipers you have to shim. You can spend a lot of time trying to get the "right" amount of shims in place...
Mean people suck.
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Re: Disc Brake question

Postby Ken » Sun Mar 14, 2010 6:02 pm

Bike night? Disc brake knowledgeable peops in attendance? When / where? I'll bring enough beer... for myself :obscene-drinkingbeer:
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Re: Disc Brake question

Postby greenfast » Sun Mar 14, 2010 10:11 pm

I will take a look and see if I can straighten it out some, thanks for the advise. If that doesn't work it might be time for a wrenching night :obscene-drinkingcheers:
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Re: Disc Brake question

Postby Farmboy » Sun Mar 14, 2010 10:14 pm

As soon as my new crank is here, I'm gonna have a little wrenchin action goin' on my my geeeerage.
If you're gonna be dumb, you better be tough.
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Re: Disc Brake question

Postby greenfast » Sun Mar 14, 2010 10:19 pm

Farmboy wrote:As soon as my new crank is here, I'm gonna have a little wrenchin action goin' on my my geeeerage.


Post up when that is and if I haven't figured this out by then maybe we can look at it.
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Re: Disc Brake question

Postby NoyzSource » Mon Mar 15, 2010 10:34 am

please be next Friday or Saturday or Sunday, please please please!

I told a guy I would help him move on Saturday but would love to get some wrenching done.

I need some chain advice, rear tire advice, and cleanliness advice.

I'll bring my bike work stand if it is needed.
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