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your god hates me
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So I just replaced all four pads on my Trek hybrid's cantilever brakes (...for the first time in eleven years, he admits sheepishly).

Recognizing the potential for my own mechanical ineptitude, I then brought the bike into the LBS to have them adjust the brakes: center them, set the spacing, tweak the cable tension, whatever the heck professional wrenches do when an idiot like me brings a bike in and says "Brakes Need Adjusting."

And they did a fine job, inasmuch as the bike stops firmly, assuredly, and decisively. Except the front brake also makes A GODAWFUL CATERWAULING SQUEAL when I use it. I'm talking serious diesel bus/garbage truck kind of brake squealing, a louder, more horrific shreiking than even war-mongering banshees would emit. It's deafening, it's embarassing, and it's relentless. Mostly happens when I'm going down hill and/or coming to a quick stop. Once it starts, no matter how gently I try modulating the brakes, it just keeps going, like a siren. People four blocks away are ducking & covering.

And the back brakes, which are the exact same pad, are perfectly silent.

Any ideas? I beg of you...my ride partners beseech you...my neighbors implore you.

Thanks.
 

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Resident Curmudgeon
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13,390 Posts
fmw said:
Brakes tend to squeak when the pads on both sides contact the rim evenly across the entire length of the pad. The pads should be angled a little with respect to the rims. You will probably notice that on your rear brakes. They weren't adjusted very well. Take care.
I agree. The brake arms/pads should be slightly "toed in." Aluminum does not like to bend, so if you're going to do this yourself, be careful. You might also try taking a piece of sandpaper & sand the rubber pads a little. Also ck the braking surface of your rims. If they're dirty, (or even if they aren't), clean them off with some fine steel wool. I'd also ck the brake arms where they're attached to the forks/stays. Make sure they're not loose or wobbley. If that still doesn't work, I'd try different pads.
 

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Are the rims clean?

Silly question, but are the rims clean? Your LBS should have spotted this. You might have residue built up on your rims from your old pads. I had a terrible time with squealing brakes when I went from Campy pads to Kool Stop. I gave my rims a good cleaning with Windex. I also stopped using Simple Green to clean my rims, there is something in Simple Green that makes the Kool Stop pads squeak. I found plain old Windex and a lot of elbow grease the first time around will remove the residue, after that I just wipe them down after each ride using Windex...I guess there is other stuff that will work just as well, I just happened to have a lot of Windex sitting around...
 

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I second the cleaning suggestion

I use rubbing alcohol -- evaporates cleanly, and doesn't hurt tires.

To do away forever with the crude "bend the arms" method of adjusting toe-in, try some Kool-Stop brake shoes (the whole unit, not just the pads -- though the pads are way better than Shimano or Campy, too).
http://sheldonbrown.com/harris/brakeshoes.html#threaded
They have spherical washers that allow you to adjust the angle with great precision, without bending anything.
 

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Master Bike Mechanic
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The Problem is most likely a combination of a Dirty Rim and New, clean brake pads, as said already, clean the rim thouroghly and sand the pad till the mold marks are gone, after that if the brakes still squeak, ride more, it always works for me, it alcimates the pads to the rims.

The advise about Toe in is also good. Kool-Stop Salmon pads offer the best stopping power FYI.
 
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