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V Brake brake squeal- tried everything!

Old 06-08-13, 10:25 AM
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V Brake brake squeal- tried everything!

I have just fitted new pads to a 10 year old commuter type bike.
I've thoroughly cleaned the rim with alcohol and have tried lightly sandpapering the surface to remove any debris.
I have tried toeing in a little, toeing in LOADS, toeing in none at all, but I'm still getting squeal.

Is it a sign or an old rim that just needs replacing or does anyone have any other tips to eliminate squeal?

The rim in question is the front.
I fitted a new rear wheel with the same new brake pads and it's working great and squeal free!
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Old 06-08-13, 11:14 AM
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The squeal is evidence of quality pads and a clean rim producing good friction.

When you apply brakes, the forward motion of the rims carries the shoes with it rotating them in an arc around the mounts, or taking the whole arm also. At some point it reaches sort of a critical mass, and the shoe slips on the rim and rotates back to the starting place. This happens at high frequency producing the classic brake squeal.

Kool Stop (and others) use pads with longer tails as a counter measure to reduce the rotation and it helps, but the only thing that stops it is increased force forcing the shoes flat to the rim. This is why shoes tend to squeal in soft speed control mode, but stop squealing in a hard braking.

The higher the pad to rim friction (a good thing) the greater the force needed to prevent squeal. So the best performing pad/rim combination will squeal unless you apply the brakes almost hard enough to cause a header.

Front canti brakes are the most prone to squealing because the studs are flexed toe out by the reaction force, adding to the issue. This is one reason folks use brake boosters.

If you live with it a while the squeal will resolve, as the shoes break in. You can speed up the process, and possibly eliminate the squeal immediately by filing a bevel or ski-tip curve into the back edge, so it cannot dig in as the shoe is pushed forward (works for the same reason a new chalk squeals on a blackboard, and slightly used one doesn't). I consider this a last resort if you ride in all weather conditions because it worsens wet performance.

Anyway, think of the bright side. You now have an automatic horn, that sounds whenever people get in your way forcing you to slow down suddenly.
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Old 06-08-13, 11:24 AM
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Along the lines of FB, I had my loaded-tour bike built from heavier material ie, from tandem stuff
thicker 4130 tube for frame and fork .. Zero squeal, from very strong Scott-Petersen SE cantilevers..

You may benefit from booster arches on the brake studs. that braces against brake boss spread.


My Magura HS 33 hydraulic rim brakes dont squeal, their slave cylinders fit on V brake
bosses, and they are braced against boss spreading..

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Old 06-08-13, 12:10 PM
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My cure for squeal is to squeez a pinch of dirt in between the rim and pads then apply the brakes for a bit. This cuts the friction to a degree but more often then not also cuts the squeal. Andy.
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Old 06-08-13, 12:18 PM
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Originally Posted by Andrew R Stewart
My cure for squeal is to squeez a pinch of dirt in between the rim and pads then apply the brakes for a bit. This cuts the friction to a degree but more often then not also cuts the squeal. Andy.
As I said, higher friction increases squeal. So this works, but it's question of degree, and one must balance the desire for maximum braking performance, vs squeal. If you have good hand strength, this might be a decent remedy, but I wouldn't suggest it for a woman or anyone with small hands.
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Old 06-08-13, 01:16 PM
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With toe in, less is more. You should only have the pads toed in the slightest amount - but you're telling us that you've done that (along with various other settings)

Taking the brake arms off and greasing the posts helps a bit sometimes.

I had one bike which gets terrible squeal and fork shudder, in the end salmon koolstops quietened it down - but it insists on a diet of newish ones, with other bikes finishing the pads off.
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Old 06-08-13, 01:16 PM
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Old 06-09-13, 06:23 PM
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Originally Posted by FBinNY
The squeal is evidence of quality pads and a clean rim producing good friction.
Nope. Cheap pads that are hard and/or old will squeal so much that pigs say "it squeals like bicycle brakes". They aren't quality pads by any stretch of the imagination. By the same token, a steel rim will squeal more than an aluminum rim and a steel rim is probably about as clean as you'll find any rim. They are so clean and polished that they gleam. But they squeal.

And dirty pads and rims chatter more than clean ones.

Originally Posted by FBinNY
When you apply brakes, the forward motion of the rims carries the shoes with it rotating them in an arc around the mounts, or taking the whole arm also. At some point it reaches sort of a critical mass, and the shoe slips on the rim and rotates back to the starting place. This happens at high frequency producing the classic brake squeal.
So far so good but incomplete. If the toe of the brake hits the rim first, there is less of a tendency for the brake pad to slip and chatter than if the tail or even the body of the shoe its first. If the toe of the brake shoe isn't sufficiently planted on the rim, the toe will tend to lift and chatter more like you've described. A good pad and a clean rim shouldn't chatter at all if properly toed-in while an old pad (ground flatter and dirtier) will chatter more. Wet brakes which are hardly the paragon of clean brakes chatter more because the toe can lift more due to the lubricating abilities of the water.

Originally Posted by FBinNY
Kool Stop (and others) use pads with longer tails as a counter measure to reduce the rotation and it helps, but the only thing that stops it is increased force forcing the shoes flat to the rim. This is why shoes tend to squeal in soft speed control mode, but stop squealing in a hard braking.
No, not really. A longer tail helps like you say but it does so by dampening the vibration of the front of the shoe. Forcing the pad flatter to the rim only results in more lift of the front of the shoe and more chatter, i.e. squealing. One way to reduce the squeal at slow speeds is to use a dual compound shoe like the Kool Stop MTB shoe. The softer material of the front of the pad doesn't squeal as much during slow braking...if proper toed...and the harder compound provides more friction as the tail of the brake shoe gets involved.

Originally Posted by FBinNY
The higher the pad to rim friction (a good thing) the greater the force needed to prevent squeal. So the best performing pad/rim combination will squeal unless you apply the brakes almost hard enough to cause a header.
Really not really. You should never need to 'almost...cause a header' to brake. It's just not necessary. And a squealy brake isn't an indicator of a superior brake. It's usually just the opposite. Yes, you do what good friction but a squeal from the brakes doesn't indicate that.

Originally Posted by FBinNY
Front canti brakes are the most prone to squealing because the studs are flexed toe out by the reaction force, adding to the issue. This is one reason folks use brake boosters.
No, again. There are lots and lots of front cantilever brakes that can be used without the brakes squealing and there are lots of cantilevers that are problem squealers. I've had Avid's Shorty 4 that were almost the worst offenders ever made. I mounted Paul's cantilevers on the same bike and the squeal went away. Same fork, different brakes. The problem was with the way in which the Shortys were designed and constructed and not with the fork that I used them on. I've had similar experiences with Shimano's first XT linear brake. The parallelogram of the brake allowed the pad to chatter all over the place. Replacing the XT brake with an Avid brake (linear brake not a Shorty) stopped the squeal instantaneously.

Originally Posted by FBinNY
If you live with it a while the squeal will resolve, as the shoes break in. You can speed up the process, and possibly eliminate the squeal immediately by filing a bevel or ski-tip curve into the back edge, so it cannot dig in as the shoe is pushed forward (works for the same reason a new chalk squeals on a blackboard, and slightly used one doesn't). I consider this a last resort if you ride in all weather conditions because it worsens wet performance.
You can speed up the process by doing what you suggest but that's only because it increase the toe-in on the pad. You shouldn't have to wait for the brakes to 'break in'. If anything old brakes that started life squealing will only get worse with age.

I've had the best luck with stopping squealing...with the Shortys it was only temporary...by going to the Kool Stop dual compound pads. Trust me as a former owner of Shorty 4 brakes, thegreatbelow, it's about the only way to cure the problem.
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Old 06-09-13, 06:38 PM
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I won't bother responding. Cyccommute already knows everything, and nobody else cares. In short I stand on my original post, and further argument is pointless. Readers are free to form whatever opinions they choose.
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Old 06-09-13, 07:43 PM
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Have you checked that the pads are installed on the correct sides? I had some koolstops that were squealing and found I had the pads on the wrong sides. I reinstalled them correctly and it solved the problem.
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Old 06-09-13, 09:18 PM
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Originally Posted by FBinNY
I won't bother responding. Cyccommute already knows everything, and nobody else cares. In short I stand on my original post, and further argument is pointless. Readers are free to form whatever opinions they choose.
Sorry but "just live with it" isn't very helpful. If that were so, then why don't all brakes squeal? Why isn't a squealing brake an indicator of excellent brakes?

And I don't proport to know everything but I do know somethings. I agree that readers are free to form whatever opinions they choose. I just ask them to think about what you have said...just live with it...and what I said...it's fixable and not necessarily normal.
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Old 06-09-13, 09:32 PM
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I suggested a few remedies, along with an explanation of the causes. The live with it a while was an alternative if the OP didn't want to keep trying to fix it. And anticipating you, the "automatic horn" reference was tongue in cheek.

The fix for squeal is rigidity, and stability. However solving squeal on front Cantis is often very to hard because there's little one can do to stiffen the fork and prevent boss spread. Boosters do help, but many people don't want them.
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Old 06-09-13, 09:44 PM
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I have a LWB recumbent with a 20" front wheel. I never could get KoolStops to shut up on the front wheel, no matter how carefully I toed them in, out or whatever. I finally got softer pads (Avid Pros) and with minimal effort in setting them up; NO NOISE, ever. bk
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Old 06-09-13, 09:47 PM
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Originally Posted by thegreatbelow
I have just fitted new pads to a 10 year old commuter type bike.
I've thoroughly cleaned the rim with alcohol and have tried lightly sandpapering the surface to remove any debris.
I have tried toeing in a little, toeing in LOADS, toeing in none at all, but I'm still getting squeal.

Is it a sign or an old rim that just needs replacing or does anyone have any other tips to eliminate squeal?

The rim in question is the front.
I fitted a new rear wheel with the same new brake pads and it's working great and squeal free!
Rear wheels seldom squeal due to the physics of braking. I doubt that your squealing problem is due to the age of the rim. You might try something else to clean the rim other then alcohol. Alcohol remove water soluble contaminants. Your squealing problem may be due to oils from the road. Try cleaning the rims with a nonpolar solvent like mineral spirits. It does a better job of removing oils than alcohols do.

Your new pads may also be part of the problem. Hard pads really squeal more than soft ones and aren't necessarily better pads. The Kool Stop salmon pads, for example, really do squeal more than something like the softer black pads. That's what makes the Kool Stop dual compound really do work better. The soft toe doesn't vibrate as much and cuts down on the squeal.
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Old 06-09-13, 10:16 PM
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Originally Posted by FBinNY
I suggested a few remedies, along with an explanation of the causes. The live with it a while was an alternative if the OP didn't want to keep trying to fix it. And anticipating you, the "automatic horn" reference was tongue in cheek.

The fix for squeal is rigidity, and stability. However solving squeal on front Cantis is often very to hard because there's little one can do to stiffen the fork and prevent boss spread. Boosters do help, but many people don't want them.
As I pointed out, your remedies and suggestions weren't correct. Based upon thegreatbelow's post, I assume that his problem started with the new pads. Logic dictates that if the brakes didn't squeal before then the stiffness of the fork and the possible spread of the bosses isn't the cause of the problem.

As for brake boosters, they were a band-aid back in the days cantilevers (different mechanism from linear brakes, by the way) and under build frames. Modern frame which include frames from 2003 were built to handle the stresses of linear brakes better and don't need brake boosters. Frankly, I've owned and ridden about a dozen mountain bikes since 1983 and not a single one of them has needed a brake booster.
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Old 06-09-13, 10:23 PM
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I've had intractable squeal occur on a couple different bikes with Kool-Stop salmon pads. In every case, switching to Kool-Stop black pads cured the squeal.
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Old 06-09-13, 10:54 PM
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Originally Posted by cyccommute
As I pointed out, your remedies and suggestions weren't correct. .

For the record, that should read you THINK my remedies weren't correct. Likewise, I THINK you're wrong.

You're free to believe whatever you want, and I won't waste my time trying to explain the physics to you, because you already believe what you believe. We can debate this until the cows come home, but why bother.

However, you might want to consider what forces act to lift the toes away from the rim, then work backward from there. You'll find that an increase of the coefficient of friction between the pad and rim increases the shoe torque compared with the down force applied by the brake. Everything follows from there.

Folks with an understanding of basic mechanics don't need to choose sides, or believe either of us. They can draw a free body diagram of the brake shoes, rim and brake arms, then draw their conclusions for themselves.
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Old 06-10-13, 04:21 AM
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Originally Posted by FBinNY

Folks with an understanding of basic mechanics don't need to choose sides, or believe either of us. They can draw a free body diagram of the brake shoes, rim and brake arms, then draw their conclusions for themselves.
This. My dynamics lecturer actually did exactly that earlier this semester, to explain why brake squeal happens. The guy's been doing this kind of thing for a living for multiple decades, so I doubt he got it wrong in some way, and his explanation was the same as FB's.

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Old 06-10-13, 04:19 PM
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Originally Posted by Jeff Wills
I've had intractable squeal occur on a couple different bikes with Kool-Stop salmon pads. In every case, switching to Kool-Stop black pads cured the squeal.
Exactly. The salmon pads are harder and thus their friction is less than a softer pad. They are also stiffer so that when they do flex as all brake pads do, they can lift the whole body of the pad off the rim and result in more chatter, not less. Any hard pad...be it old or be it designed to have a hard durometer rating...is naturally going to squeal more because of the hardness of the rubber.
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Old 06-10-13, 04:24 PM
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Originally Posted by FBinNY
... I won't waste my time trying to explain the physics to you, because you already believe what you believe. We can debate this until the cows come home, but why bother.

However, you might want to consider what forces act to lift the toes away from the rim, then work backward from there. You'll find that an increase of the coefficient of friction between the pad and rim increases the shoe torque compared with the down force applied by the brake. Everything follows from there.

Folks with an understanding of basic mechanics don't need to choose sides, or believe either of us. They can draw a free body diagram of the brake shoes, rim and brake arms, then draw their conclusions for themselves.
I did not say that your physics was wrong. Physics isn't everything either. There is chemistry of the polymer used to make the brake pads involved here as well. There may even be the chemistry of the grease/oil and the brake pad and an inappropriate solvent usage. That's one place where you went wrong. And there ain't no free body diagram to explain that.

That and saying that brake squeal is a sign of 'quality'. I've never met a person that thought that brake squeal was a sign of anything good. Everyone that has experienced it goes out of their way to get rid of it.
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