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Caliper brakes, front ones started squealing. Tried the following:

  1. Cleaned rim with rubbing alcohol and a cloth.
  2. Tightened all bolts.
  3. Replaced brake pads with new ones.
  4. Adjusted to ensure alignment is right.
  5. Toe-ing in the brakes just made the squeal worse.

My rear brakes have no problem, even though I've replaced them myself, so my setup shouldn't be that bad. The only remaining thing I can think of is the front wheel has a very slight wobble, presumably my next step would be to try and true the wheel a touch. Just wanted to get some expert opinions before I spend more time on this, as all the usual solutions have failed.

Thanks!

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  • What in the brakes did you replace? The entire brakes, or the breakpads? – Luuklag Sep 7 '20 at 7:33
  • Truing the wheel should fix the squeal. – Carel Sep 7 '20 at 7:37
  • Very new brakepads could squal for the first few kilometers, unitll they are worn a little. – Luuklag Sep 7 '20 at 7:42
  • Replaced just the brake-pads. Regarding very new brakepads - possible. However, I tried moving the rear brake pads to the front and installed the new pads on the rear tire. The new pads on the rear tire didn't squeal, but the old rear pads on the front squealed. So it seems like a result of the something other than the brake pad, but I'm a newb so I could be wrong – BoB Sep 7 '20 at 7:55
  • If putting new pads in the back fixed the problem there and moving old pads to front didn't, it just might make sense to try new pads in front too. – ojs Sep 7 '20 at 9:17
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  1. Replaced brake pads with new ones.

Try a different brake pad material. Don't just blindly replace brake pads with new equivalents of what you currently have. Try a different material.

I used to prefer Kool Stop Salmon colored pads on all bikes I owned. However, on one of my bikes, Kool Stop Salmon pad squealed in the front cantilever brake like hell. I even tried a dual compound Kool Stop pad (consisting of half Salmon and half black compound) but didn't help.

The solution was to use the standard Shimano S70C pad in the front attached to the Shimano brake pad holder.

I don't know if the cause was the different brake pad holder (the Kool Stop pads were integral design, not separate rubber pieces put into a holder), or different brake pad material.

Yet, this Shimano holder combined with S70C pad solved the issue with me. Unfortunately, the Shimano pad does not resist grit intrusion in as good manner as the Kool Stop Salmon pad resists, but it's acceptable.

Keep trying! Experiment with different kinds of brake pad materials and holder designs from different manufacturers.

The only remaining thing I can think of is the front wheel has a very slight wobble, presumably my next step would be to try and true the wheel a touch

If the squealing is continuous around the wheel rotation and not intermittent, fixing a very slight wobble in the wheel probably won't help. Squealing brakes cannot magically know whether:

  • There is a wobble 180 degrees away, so they should squeal
  • There is no wobble 180 degrees away, so they should not squeal

The point is that brakes are local. A wobble is local too, and thus wobble will squeal only at the wobble, not all around the wheel. Wobble-dependent continuous squeal would be spooky action at a distance.

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  • Thanks for your comments! Regarding wobble, yes this thought crossed my mind, as indeed the squeal happens regardless of when I hit the brakes. Nevertheless, I true-ed the wheel slightly yesterday just for kicks, still no luck. I just find it odd that one tire should be fine with this type of pad, but the other not, don't you? Sounds expensive to keep trying different pads :-) But maybe this is the only option I have left. Or just take it to the bike shop and let them figure it out, might be cheaper in the long run? – BoB Sep 8 '20 at 7:24
  • It's the environment where the brakes are attached that matters. The rear triangle can have different flex properties at the mounting bolt than the front fork has. I don't think there's any other option than to try few different pad compounds. – juhist Sep 8 '20 at 8:31
  • Also here are some hints that could help: sheldonbrown.com/brandt/brake-squeal.html – juhist Sep 8 '20 at 8:35
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The biggest thing not mentioned in the list of things you've tried is adjusting the pivot slop in the brake.

Different caliper brakes have different procedures for this.

I don't have a pithy explanation of the physics I can stand behind. It probably also varies for different brake models/designs. But it makes a difference in squeal in some circumstances.

Reverse toeing the pads can sometimes also eliminate squeal, but it does so at the expense of creating poor contact with the rim.

Also it's important to understand that twisting the arms the traditional way is a good and normal thing to do on some brakes (older and/or cheaper generally) to eliminate squeal, but shouldn't be done on most contemporary brakes. How to differentiate is its own question.

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  • Thanks for the suggestion! I can't seem to track down "pivot stop" on any bike repair pages. Is there a more formal term one uses for this, so that I can look up how to do it? – BoB Sep 10 '20 at 6:16
  • Play or looseness in pivots would be other terms. A look at how most dual pivot brakes do it is in section 8 of parktool.com/blog/repair-help/dual-pivot-brake-service . But there really is quite a bit of variance among brake models and manufacturers won't usually document it; it's more something you just look at how the brake works and do. You're generally shooting for as loose as possible with either no free play or just the barest perceptible amount. – Nathan Knutson Sep 10 '20 at 7:26

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