What causes rim brakes to shriek?

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Mububban
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What causes rim brakes to shriek?

Postby Mububban » Sat Oct 20, 2018 11:01 pm

My wife bought one of the Aldi folding bikes recently, and the front brake shrieks when stopping. Not the rear, just the front brake. It's brand new, it works, it's not overly grabby or too weak. There's no pulsing of the brake to indicate any warping of the rim. Just a fairly loud shriek that I've personally never encountered on a rim brake before.

Any ideas what might cause this, and what I could try to fix it? Is it just because it's so new, and it'll bed in shortly? I've tried doing repeated braking efforts but the sound hasn't changed so far.
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Thoglette
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Re: What causes rim brakes to shriek?

Postby Thoglette » Sun Oct 21, 2018 12:01 am

If it's not a design problem or loose bolts, it's most likely toe in. See Sheldon's article
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Tamiya
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Re: What causes rim brakes to shriek?

Postby Tamiya » Sun Oct 21, 2018 12:20 am

If I had tools lying out I'd be tempted to try swapping brake pads front to rear.

If all I had nearest to hand was a spray bottle of Windex... use it to clean the rim & brake pads.

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bychosis
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Re: What causes rim brakes to shriek?

Postby bychosis » Sun Oct 21, 2018 6:40 am

Plus one for checking toe in.
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Duck!
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Re: What causes rim brakes to shriek?

Postby Duck! » Sun Oct 21, 2018 10:10 pm

Plus another for toe adjustment. Just to clarify, you want the front end of the pads just slightly closer to the rim than the trailing end so they form a V, with the rotating rim entering from the open end.
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DavidS
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Re: What causes rim brakes to shriek?

Postby DavidS » Mon Oct 22, 2018 8:05 pm

Mine shriek too on a roadie with V brakes and I have the pads toed in. Sometimes it just seems to happen. Pain though.

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AUbicycles
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Re: What causes rim brakes to shriek?

Postby AUbicycles » Tue Oct 23, 2018 3:55 am

A roadie with V-brakes? Like an older CX bike?

Again toe-in. The only tools are an Allen Key and patience..

Neddysmith
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Re: What causes rim brakes to shriek?

Postby Neddysmith » Tue Oct 23, 2018 8:58 am

My brakes are great and dont have any problems braking in general, however, i have found they shriek when heavy braking after longer descents, so for mine it seems one the rim has heated, cant seem to get it happening when braking hard on the flat.

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Re: What causes rim brakes to shriek?

Postby Trevtassie » Tue Oct 23, 2018 10:08 am

My secret for setting toe in is to use a loose zip tie of appropriate thickness around the end of the pad. With post mounts I put identical pieces of stiff plastic hose on the posts (between the pad and the locking bolt) so you don't need to be an octopus to adjust them. Post mounts were invented by a moron I think...
Loose the nuts, squeeze the brakes, tighten the nuts then take off the zip ties. That way you can be scientific with controlled gaps, still squealing, use a thicker zip tie.

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Re: What causes rim brakes to shriek?

Postby RobertL » Tue Oct 23, 2018 10:14 am

Trevtassie wrote:My secret for setting toe in is to use a loose zip tie of appropriate thickness around the end of the pad. With post mounts I put identical pieces of stiff plastic hose on the posts (between the pad and the locking bolt) so you don't need to be an octopus to adjust them. Post mounts were invented by a moron I think...
Loose the nuts, squeeze the brakes, tighten the nuts then take off the zip ties. That way you can be scientific with controlled gaps, still squealing, use a thicker zip tie.


I use a folded up piece of card - whatever I have lying around that's about the right thickness. Same principle, though.
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Re: What causes rim brakes to shriek?

Postby DavidS » Tue Oct 23, 2018 9:10 pm

AUbicycles wrote:A roadie with V-brakes? Like an older CX bike?

Again toe-in. The only tools are an Allen Key and patience..


Maybe more of a touring bike, Allegro T1.

Yeah, have toed in a fair bit, very fiddly on V Brakes.

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Mububban
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Re: What causes rim brakes to shriek?

Postby Mububban » Wed Oct 24, 2018 11:42 pm

Thanks for the info everyone. I've cleaned the rim (although the bike is brand new out of the box) - no change. Tried toeing in the pads using layers of cardboard - no luck. One pad seems to toe in well, but the other wants to stay flat, and shrieking up and down the street at 8pm isn't very neighbourly so I'll try again tomorrow.

Next step will be to try roughing up the pad surface. Failing that, take it into the LBS when I pick up my bike from service on Friday :)
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Re: What causes rim brakes to shriek?

Postby Neddysmith » Thu Oct 25, 2018 9:08 am

One other thing you could try is just changing the brake pads, on the boys bmx i had a similar issue, cleaned brake pads and rims, adjusted toe in, roughed pads, etc etc etc nothing would stop it, changed front ad rear brake pads still the same, then bought new pads different compound and has been great ever since.

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Re: What causes rim brakes to shriek?

Postby Thoglette » Thu Oct 25, 2018 10:16 am

Mububban wrote:but the other wants to stay flat


Some brute force is called for to either bend or reshape the brake arm
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P!N20
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Re: What causes rim brakes to shriek?

Postby P!N20 » Thu Oct 25, 2018 10:32 am

Disc brakes are the only sensible solution here.

</sarcasm>

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Re: What causes rim brakes to shriek?

Postby kb » Tue Nov 27, 2018 9:19 am

P!N20 wrote:Disc brakes are the only sensible solution here.

</sarcasm>

You misspelled “fixie” ;-)
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Mububban
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Re: What causes rim brakes to shriek?

Postby Mububban » Tue Nov 27, 2018 3:46 pm

I ended up toeing in the front pads a bit more, and it helped reduce the noise a lot. I wasn't game to try bending cheap brakes as I've heard of them snapping.

In fact, the brakes don't squeal at all now, because my wife hasn't ridden it once since we bought it :D
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cyclotaur
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Re: What causes rim brakes to shriek?

Postby cyclotaur » Tue Nov 27, 2018 6:13 pm

DavidS wrote:Mine shriek too on a roadie with V brakes and I have the pads toed in. Sometimes it just seems to happen. Pain though.

DS


I ride a CX with noisy cantis (they are 7 years old....) and was considering an 'upgrade' to new mini-Vs to reduce noise and improve braking performance.

Hope I'm on the right track... :|
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Re: What causes rim brakes to shriek?

Postby ValleyForge » Wed Nov 28, 2018 11:03 pm

cyclotaur wrote:
DavidS wrote:Mine shriek too on a roadie with V brakes and I have the pads toed in. Sometimes it just seems to happen. Pain though.

DS


I ride a CX with noisy cantis (they are 7 years old....) and was considering an 'upgrade' to new mini-Vs to reduce noise and improve braking performance.

Hope I'm on the right track... :|

Look for a pair of pads that have elliptical washers on them - KoolStop were my preference for the MTB I had in the 90s with V-brakes. Bloody good brakes and the pads are easy to set toe in with.
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Re: What causes rim brakes to shriek?

Postby Thoglette » Thu Nov 29, 2018 10:14 am

ValleyForge wrote:Look for a pair of pads that have elliptical washers on them - KoolStop were my preference for the MTB I had in the 90s with V-brakes. Bloody good brakes and the pads are easy to set toe in with.

+1
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cyclotaur
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Re: What causes rim brakes to shriek?

Postby cyclotaur » Thu Nov 29, 2018 2:44 pm

Thoglette wrote:
ValleyForge wrote:Look for a pair of pads that have elliptical washers on them - KoolStop were my preference for the MTB I had in the 90s with V-brakes. Bloody good brakes and the pads are easy to set toe in with.

+1

Er…..elliptical washers. Right. :?
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Re: What causes rim brakes to shriek?

Postby ironhanglider » Thu Nov 29, 2018 9:49 pm

cyclotaur wrote:
Thoglette wrote:
ValleyForge wrote:Look for a pair of pads that have elliptical washers on them - KoolStop were my preference for the MTB I had in the 90s with V-brakes. Bloody good brakes and the pads are easy to set toe in with.

+1

Er…..elliptical washers. Right. :?


I suspect that he was referring to the concave/convex combinations which allow the pad to be fixed an an angle rather than at only perpendicular to the brake arm. There are many variations on the theme for all styles of rim brakes.

Cheers,

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Re: What causes rim brakes to shriek?

Postby ValleyForge » Fri Nov 30, 2018 10:35 am

ironhanglider wrote:
cyclotaur wrote:
Thoglette wrote:+1

Er…..elliptical washers. Right. :?


I suspect that he was referring to the concave/convex combinations which allow the pad to be fixed an an angle rather than at only perpendicular to the brake arm. There are many variations on the theme for all styles of rim brakes.

Cheers,

Cameron

Apologies if it's not a commonly used term. Try these - you can see the nature of the washers. http://www.koolstop.com/images/CXT.jpg
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Re: What causes rim brakes to shriek?

Postby Bunged Knee » Fri Nov 30, 2018 11:40 am

This is the name of the washers.
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Re: What causes rim brakes to shriek?

Postby cyclotaur » Fri Nov 30, 2018 1:57 pm

Well....I picked up an allen key and reset the toe-in and all is well. Silent ride, except for the gentle whirr of the drive train and the crunch of tyres on gravel. 8)
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