What causes rim brakes to shriek?

User avatar
Mububban
Posts: 1553
Joined: Wed Feb 20, 2008 12:19 pm

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.
When you are driving your car, you are not stuck IN traffic - you ARE the traffic!!!

User avatar
Thoglette
Posts: 4320
Joined: Thu Feb 19, 2009 1:01 pm

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
Stop handing them the stick! - Dave Moulton
"People are worthy of respect, ideas are not." Peter Ellerton, UQ

Tamiya
Posts: 124
Joined: Mon May 28, 2018 12:15 am

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.

User avatar
bychosis
Posts: 5709
Joined: Sat Jan 14, 2012 1:10 pm
Location: Lake Macquarie

Re: What causes rim brakes to shriek?

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

Plus one for checking toe in.
bychosis (bahy-koh-sis): A mental disorder of delusions indicating impaired contact with a reality of no bicycles.

User avatar
Duck!
Expert
Posts: 7095
Joined: Tue May 21, 2013 8:21 pm
Location: On The Tools

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.
I had a thought, but it got run over as it crossed my mind.

User avatar
DavidS
Posts: 2489
Joined: Wed Sep 22, 2010 11:24 pm
Location: Melbourne

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.

DS
Image

Cannondale Quick Speed 2, Allegro T1

User avatar
AUbicycles
Site Admin
Site Admin
Posts: 13294
Joined: Tue Aug 23, 2005 2:14 am
Location: Sydney & Frankfurt
Contact:

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
Posts: 109
Joined: Mon Jun 26, 2017 11:10 am

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.

Trevtassie
Posts: 681
Joined: Sun Jun 28, 2015 10:57 am

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.

RobertL
Posts: 730
Joined: Wed Feb 17, 2016 3:08 pm
Location: Brisbane

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.
Image

User avatar
DavidS
Posts: 2489
Joined: Wed Sep 22, 2010 11:24 pm
Location: Melbourne

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.

DS
Image

Cannondale Quick Speed 2, Allegro T1

User avatar
Mububban
Posts: 1553
Joined: Wed Feb 20, 2008 12:19 pm

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 :)
When you are driving your car, you are not stuck IN traffic - you ARE the traffic!!!

Neddysmith
Posts: 109
Joined: Mon Jun 26, 2017 11:10 am

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.

User avatar
Thoglette
Posts: 4320
Joined: Thu Feb 19, 2009 1:01 pm

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
Stop handing them the stick! - Dave Moulton
"People are worthy of respect, ideas are not." Peter Ellerton, UQ

User avatar
P!N20
Posts: 934
Joined: Thu Jul 22, 2010 6:50 pm

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>

Who is online

Users browsing this forum: No registered users