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Single Pivot Brake Squeal

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Old 03-14-19, 04:49 PM
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P!N20
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Single Pivot Brake Squeal

I'm running Campy Chorus Monoplaner single pivot brakes with Koolstop KS-CR pads in the original, er, holders. Rims are H Plus Son TB14.

They look awesome, but they squeal like a mother****er. Front and rear.

I know I need to toe them in, but what's the best way to do that?

1. Get new holders and pads that can be toed in? (But I really like the 'original' blocks)
2. Twist the caliper arms? (There's part of me that doesn't like this, but I guess it's only a minor adjustment.)
3. Any other options? Can the original pads/holders be toed in?

Cheers.

Sorry if this has been done to death.
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Old 03-14-19, 04:57 PM
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We used to toe in the arms by bending them slightly using a crescent wrench with something like cardboard or tape to protect the finish.
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Old 03-14-19, 06:43 PM
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Aluminum does not take kindly to being bent. Bend it enough times and it will snap. I toe in pads by sanding the pads. No need to mess with the metal. I've seldom had to do this though, no matter whether it's my Campy, Suntour Superbe or Shimano brakes. Oftentimes the source of squeal is not having the pivot bolt tight enough which results in play and oscillation of the brake arms.

Also, any chance you have contamination on the rims or pads? I've had horrendous squeals occur from getting lubricant on the rims and it has sometimes taken me a lot of scrubbing and several attempts to get them truly clean. I also ran over and burst a tube of sunscreen once. It took weeks to get that stuff out of the pads.
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Old 03-14-19, 06:46 PM
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Originally Posted by Fivethumbs View Post
We used to toe in the arms by bending them slightly using a crescent wrench with something like cardboard or tape to protect the finish.
+1 Doesn't cause premature pad wear as sanding them would.
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Old 03-14-19, 06:48 PM
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Originally Posted by oddjob2 View Post
+1 Doesn't cause premature pad wear as sanding them would.
But does cause premature snapping of the brake arm if the yield strength is exceeded...easily done with aluminum. Brake pads are cheap.
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Old 03-14-19, 06:53 PM
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Originally Posted by davester View Post
Oftentimes the source of squeal is not having the pivot bolt tight enough which results in play and oscillation of the brake arms.
That's interesting, I'll check that.

Originally Posted by davester View Post
Also, any chance you have contamination on the rims or pads?
Highly unlikely. It's a fairweather bike and on the rare occasion it finds itself on some wet roads I give it a good clean afterwards. Having said that I was intending to give the pads a bit of a sand just to make sure.

Thanks for the comments thus far.
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Old 03-14-19, 06:54 PM
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Originally Posted by davester View Post
But does cause premature snapping of the brake arm if the yield strength is exceeded...easily done with aluminum. Brake pads are cheap.
Yes in theory. Ir practice, I have yet to hear of a caliper snapping. I wouldn't do this to a nice Campy caliper. I'd get a toe-able pad or live with the squeal.

Ben
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Old 03-14-19, 07:08 PM
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Originally Posted by 79pmooney View Post
Yes in theory. Ir practice, I have yet to hear of a caliper snapping. I wouldn't do this to a nice Campy caliper. I'd get a toe-able pad or live with the squeal.

Ben
I had a Universal 68 caliper snap when I tried to toe it in. That cured me of the practice. Of course, those are inexpensive cast aluminum calipers so might be more susceptible to this than nice Campy calipers. On the other hand I can't imagine making this rather brutal modification to a nice Campy caliper.
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Old 03-14-19, 09:10 PM
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No, no, no! Campy sidepull brakes should not be toed in by bending the arms. Save that for your cheap Weinmanns.

Campy brakes rarely squeal unless you try to put salmon pads in them. Don't do it. Apparently same thing for whatever Koolsop KsCR pads are. Stick with stock campy pads or black koolstops. If you really must have red or dual compound, use modern adjustable pads.

If there's still squeak happening, you can sand the trailing edges of the pads a bit, and deglaze them if necessary. Sand the rims lightly. Don't hit the tires.
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Old 03-14-19, 09:33 PM
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Originally Posted by Salamandrine View Post
Campy brakes rarely squeal unless you try to put salmon pads in them. Don't do it. Apparently same thing for whatever Koolsop KsCR pads are. Stick with stock campy pads or black koolstops.
They're black:


My brakes actually came with the original Campy pads, but I swapped them for the Koolstops because they were squealing! This was on a different rim. They were OK (only squealed during really heavy braking) then I went and built a new wheelset and the squealing returned. I'm wondering if the modern machined braking surface doesn't play nice with the vintage non-toed in pads.

Maybe I should put the Campy pads back in and see what happens.

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Old 03-14-19, 09:43 PM
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Originally Posted by P!N20 View Post
They're black:

Yeah, I just googled that and found out they were the black ones. Black Koolstops aren't quite as soft as campy black pads, but they are generally close enough.

Anyway, try the other stuff. Sanding the rims always works. Slip some wet or dry under the pad and turn the wheel. I always do this while riding, but that requires decent balance and ambidexterity. Probably not the best choice for everybody. I realize it scares people now that manufacturers have convinced people that caliper brakes wear through rims, but this was the standard mechanic's trick for decades.

Let the pads bed in a bit too. Scuff the surface to get them started. Sometimes brakes won't settle down until they are well bedded.

Make sure all your pivots are well adjusted and not loose.

AFA old non machined rims - maybe. They could be a bit rougher I suppose. Resonances don't like irregularity.

The old pads probably squealed because they were old and dried out.
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Old 03-15-19, 10:53 AM
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Did you mention whether the brake pads are new or old? My experience has been that new pads, especially koolstop, tend to be soft and sticky, and will grab the rim. Grabbyness tends to promote squealing. Toe-in helps minimize this; I tend to take a little material off of the back of the pad with a file, but use any method that works (although bending the arms is not something I recommend).

Once the pads get used and age, they will harden up and be less prone to squealing. However, I find that I can get old pads to squeal on a really humid day... I guess they get soft enough to grab again.

Steve in Peoria
(there's also the issue of play in the calipers... I'm not sure how this is adjusted in the monoplaners)
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Old 03-15-19, 11:14 AM
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Originally Posted by steelbikeguy View Post
Once the pads get used and age, they will harden up and be less prone to squealing. However, I find that I can get old pads to squeal on a really humid day... I guess they get soft enough to grab again.

Steve in Peoria
(there's also the issue of play in the calipers... I'm not sure how this is adjusted in the monoplaners)
Yeah, I've experienced this too. A bit of age often helps with Koolstops.

But, when pads are really old and dried out, they become the worst screamers of all. It can take a couple decades+ for them to get to this state. So there's a sweetspot: more than a couple months, and less than a couple decades.

When I rebuilt my last PX10, I kept the original pads because they looked OK, and I had always used original pads in my previous PX10. What a difference a couple decades make. I rode it up to the top of the hill by where I lived for its maiden voyage. Didn't bother to test the brakes on the flats. Got to the top and headed down. SCREEEEECCCCHHHHH!!!! Hilarious. Probably audible from 20 miles away. And they barely slowed the bike down. It seemed like 90% of the little friction there was was simply converted to sound. It was an exciting descent. New Koolstop blacks were installed, fixed it immediately.

Oh, BTW, monoplanar pivots are adjusted just like regular brakes, but with cone wrenches. I forget the sizes. There's a lock nut and an adjusting nut. Adjust for free movement but minimum play - just like a hub.

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Old 03-15-19, 11:37 AM
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I have toed in a lot of brake calipers with the bend technique and not once has one failed! It is easy to do but keep in mind that bending aluminum DOES stress the alloy and just might start a crack in the metal. That said, there are other ways to achieve toe-in without bending...

To get the brakes to reach on my Universal rear side pull, I filed two washers, alloy of course, to a taper and installed them under my brake pad holders. Worked fine and the same idea can be used to create toe-in without possible damage...


That said, I did get lucky and this long reach side pull is waiting, in Canada, for me to get back from my Jamaica riding...


I do prefer to bend to achieve toe-in but I have been warned to be careful when it comes to the Universal brake calipers. Other than that, not much else to add except be careful.
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Old 03-15-19, 12:15 PM
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The thing about toe in is that as soon as the pads wear in a bit, it disappears. It's true that calipers were "cold set" in bike shops all the time, but this was limited to low to mid level bikes. They wouldn't be ridden typically more than 30 miles a month or so, and it might be a year or more before the pads were worn enough for the toe in to be gone. By then they were either dry enough to not be so grabby, or it was a reasonable time for a tune up.

Campy record brakes (and Chorus etc) were never toed it, at least by anyone that knew what they were doing. People that had campy usually were enthusiasts who rode every day, and wore through the pads. If you were to bend the arms for the usual ~1/16" toe in, it'd be gone in a week. So it was more or less pissin in the wind. They didn't tend to squeeak anyway, at least with stock pads. Some people would put Matthausers salmon pads on campy brakes, and those could wail pretty badly.
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Old 03-15-19, 12:46 PM
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Squeal is a vibration that is caused by play in the brake calipers. This could be caused the caliper arms rocking around the pivot bolt. Or due to overly-flexible caliper arms.

Toeing-in the pads is a kludge which serves to weaken the braking power to overcome basic deficiencies in the calipers.

Most vintage brakes have thin-profile flexy arms with inferior metallurgy. Modolo, and anything labelled: Dia-Compe immediately comes to mind. And they are usually set up poorly, such that the arms are either too tight, leading to stiff calipers and centering problems, or too loose, leading to shuddering and squeal.

As a mechanic at a large volume, big city bike Co-op, my primarily solution to this problem is to remove these brakes from recoverable bikes, and bury them deep in the trash. Since the days of dual-pivot calipers, I haven't had to suffer from squealing brakes any more.
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Old 03-15-19, 02:01 PM
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Sanding a sixteenth off the back of the pad, tapering to the front, isn't likely to reduce the useful life of the pad. They will probably harden up long before the pads are worn enough to replace. And even if you do ride enough to wear the pads down to the point they need replacing, so what? Pads are cheap, all things considered. Compared to weakening an alloy caliper arm by twisting it, replacing pads once or maybe twice is a much wiser choice.
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Old 03-15-19, 04:02 PM
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Yeah, I learned that too much bending of the brake arm is a bad thing:

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Old 03-15-19, 04:56 PM
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For folks like me riding old bikes with steel calipers, toe in, no matter how you achieve it, won't wear in as the pads wear. What happens is the front of the pad contacts the rim first and then the brake calipers flex with more pressure so the pads contact the rim evenly. The toe in adjustment doesn't change.
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Old 03-15-19, 05:03 PM
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Originally Posted by steelbikeguy View Post
Did you mention whether the brake pads are new or old?
Well, they've been on for a couple of years, but about a year with the current rims. But this is far from my every day bike, probably between 1000 - 2000 kilometers in that time, at a guess.
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Old 03-15-19, 05:05 PM
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Originally Posted by randyjawa View Post
To get the brakes to reach on my Universal rear side pull, I filed two washers, alloy of course, to a taper and installed them under my brake pad holders. Worked fine and the same idea can be used to create toe-in without possible damage...
I like the idea of tapered washers. Is this something you can buy of the shelf?
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Old 03-15-19, 05:07 PM
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Originally Posted by Dave Mayer View Post
Toeing-in the pads is a kludge which serves to weaken the braking power to overcome basic deficiencies in the calipers.

Since the days of dual-pivot calipers, I haven't had to suffer from squealing brakes any more.
But toeing in on dual pivot calipers is standard practice, isn't it? Well that's what I've always done on my dual pivots.
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Old 03-15-19, 05:13 PM
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Thanks all for the responses.

I can't detect any play in the arms, but I'll need to do a thorough check with the right tools.

I'll give the pads and rims a sand and see if that makes any difference.

I might even put the original Campy pads on just to see if it's any better or worse.

You've talked me out of twisting the arms, which to be honest I wasn't really comfortable doing anyway.

If all that yields no results I'll cut/sand the pads into a taper.

I'll report back with the results.
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Old 03-15-19, 05:43 PM
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Originally Posted by P!N20 View Post
Well, they've been on for a couple of years, but about a year with the current rims. But this is far from my every day bike, probably between 1000 - 2000 kilometers in that time, at a guess.
that reminds me... I've had more problems with shiny new rims too (or modestly new). A smooth polished surface seems to give the brake pad something to stick to... think of new Converse shoes on a freshly swept gym floor. The rubber just conforms to the surface and hangs on to it.

Honestly, the things that I love about a new bike are all the stuff that promotes squealing brakes. This was really evident when I built up a custom touring bike back in the year 2000. New rims, new cantilever brakes with koolstop salmon pads... beautiful stuff, but the brakes squealed terribly! It took a lot of toe-in to reduce the squeal, and riding in the rain a lot did put a heavy coating of crud on the brake pads, which really helped. After 35,000 miles, I recently replaced the rear pads, whereupon it did squeal a bit again.
Of course, the braking was much better than with the 18 year old pads.

Similarly, I recently had troubles with one or two of my vintage bikes. It was really only an issue on the extremely humid summer days that we sometime get here in Illinois. The bikes had fairly new rims; Mavic MA-2's and some Torelli Master rims. These are pampered bikes, so they've never encountered wet conditions. The brake pads had seen some use, but certainly weren't heavily used. The brakes were the standard Campy short reach Record brakes, and I tightened up their pivots. It was getting rather frustrating when riding with friends... I tried to minimize my braking as much as possible.
Eventually, I started a proper troubleshooting process. I swapped wheels with known non-squealers, and had some improvement. I swapped brake pads with some really ancient Mathausers and the squeal was gone.
Having identified the pads as the primary problem, I got out the file and significantly increased the degree of toe-in. That pretty much took care of the issue.

The lesson? identify all of the items that might cause the problem and carefully troubleshoot the problem. i.e be methodical, take notes, etc.
Another lesson is that it's good to have a variety of bikes, as it provides a source of parts to use when troubleshooting. Feel free to use this tip when justifying your N+1 philosophy.

Steve in Peoria
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Old 03-16-19, 10:49 AM
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I like the idea of tapered washers. Is this something you can buy of the shelf?
I made my own and my bet is that you can't buy them off of the shelf, but that is just a guess.

I made mine by filing two brake mounting washers, the kind that has a round out to accommodate the frame fit. Or, just get a couple of pieces of aluminum, shape to the size you want (might leave a wee tab to rotate for toe-in adjustment), and then file the taper. Takes about fifteen minutes.

As for toe in, it must be present or, as at minimum zero. Zero is tough to get, believe that. A pad that contacts the rim first, at the back of the pad will squeal. Toe it in a wee bit, ensuring that the front of the pad touches the rim first but do not over do it. With the front of the pad touching, you want no more, perhaps even half, of the width of the cover of a book of matches about ten thousands of an inch might be a good rule to work towards.

Anyway, that's what works for me.
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