Squealing v-brakes, help!

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bealer
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Joined: 1 Apr 2010, 1:16pm

Squealing v-brakes, help!

Post by bealer »

My front v-brakes never used to squeal but recently they've started doing so. It's actually beyond a squeal, they're full-on screeching now.

Anyway, I set about trying to solve the issue but so far without success. Things I've tried:

1) Cleaning the rims with a scotch pad and soap, then with rubbing alcohol.
2) Fresh pads. KoolStop Salmon's, and the mixed compound, and the black compound.
3) Toe-ing in and out the pads
4) Tightening all bolts
5) Changing the XT Parallel push v-brakes (notorious squealers) for a set of old LX v-brakes.
6) Tried some Tektro RX5 mini v-brakes

I just can't get rid of the squeal. The rear brakes are fine, it's just the fronts. And they were fine for well over a year before. I know some will say just accept the squeal, but it's actually too loud and probably not very efficient.

Does anyone have any tips or ideas? I was going to check the hub nut/sealers (forget the name) aren't tight enough. And check the fork is seated properly, not moving etc...

Additional info - I have a Soma Double Cross steel frame with Surly LHT forks.
I can see it driving me to the point of switching to disc forks and brakes if I can't fix it.
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Squealing v-brakes, help!

Post by Brucey »

if you have brakes that rotate on the frame boss itself (rather than having an integral pivot) then if there is any play on the pivot, a few turns of PTFE tape on the boss can help to stop squealing.

It is also worth cleaning the rims some more. Alcohol doesn't dissolve everything; it is worth wiping with a different solvent, like lighter fluid or cellulose paint thinners.

If you have cartridge pads, do be sure that the inserts are not loose in the holder; if they are not a very tight fit then they can help a squeal too.

I usually find that it takes a few really wet rides before the brakes and rims bed into one another properly. I also think that rims with a visible wear indicator cause more trouble than those without.

Finally give a thought to the thrust line through the pads; when viewed from above the pad mounting slot is normally not centred vs the pivot, and nor is the pad ( the shoe is usually asymmetric). IME a symmetric pad mounted too far forwards will squeal, as will a pad mounted too far back, too. If you have a choice of pad designs, experiment with them too.

good luck

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Valbrona
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Joined: 7 Feb 2011, 4:49pm

Re: Squealing v-brakes, help!

Post by Valbrona »

bealer wrote:3) Toe-ing in and out the pads.


You only toe brake pads in.
I should coco.
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531colin
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Location: North Yorkshire

Re: Squealing v-brakes, help!

Post by 531colin »

Image

I had that with these XT parallel push.....drove me to distraction.
In the end I took the thing to bits** and reversed it so the pads are in front of the arms (like they are on the back)
So far its been OK on 3 different bikes, with a total of 5 different forks.
Now got 2 bikes as above with ceramic rims which have a bit of a squeak from time to time, but then they are known for it, specially when new. Its not bad, I can live with it, unlike before when they would scream all day down every hill and it was unbearable....
You used to be able to get sets of shims, you were meant to undo a grub screw somewhere and pack the pivots to take out the slack....it didn't help me at all, and I don't suppose the shims are available now. I have seen 2 incarnations of XT parallel push brakes, its the older sort I have modified.

** desperation really....if I can't ride it, whats to lose? Don't do it unless you are confident you are capable...its your neck, after all!
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CREPELLO
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Joined: 29 Nov 2008, 12:55am

Re: Squealing v-brakes, help!

Post by CREPELLO »

Interesting that you've swapped the XT's for RX5's with the same result. I would suspect the brake blocks. For all the praises sung of Koolstop on these boards they can be prone to squeal. Swap for a different brand. Aztec are reputed to squeal less.

Also, although the rims look clean, try rubbing the rims down with a fine emery paper and just wipe with a damp cloth - no alcohol.
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Squealing v-brakes, help!

Post by Brucey »

531colin wrote:Image

I had that with these XT parallel push.....drove me to distraction.
In the end I took the thing to bits** and reversed it so the pads are in front of the arms (like they are on the back)....


except on the back 'in front of the arms' is 'behind' and on the front of the bike 'in front of the arms' is 'in front' which is not the same thing at all in terms of how the brake works.

I would have predicted less braking power and more uneven pad wear with a setup like that.

Shows you what I know then... :roll: :oops:

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
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531colin
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Location: North Yorkshire

Re: Squealing v-brakes, help!

Post by 531colin »

Image

You do need the "eye of faith" here to see it, but I now have the pads forwards of the brake arms on both brakes.....where "forwards" means in the direction of travel.
That's how the pads mostly are on front cantilevers, and front cantilevers mostly don't squeal as bad as rears....and rears mostly have the pads rearwards of the direction of travel. The rear XT Vees (as manufactured) have the pads forwards and don't squeal.
I like a CR720 on the rear, they don't squeal....the arm is massive, and the pad is mounted more or less centrally in the arm.

......it could all be nonsense or co-incidence, I dunno....but its working at the moment, so I ain't fixing it...... :?
bealer
Posts: 376
Joined: 1 Apr 2010, 1:16pm

Re: Squealing v-brakes, help!

Post by bealer »

Thanks for the suggestions all.

The brakes are self rotating so will leave trying the scotch tape idea. I double checked the pads. They're in super tight.

For cleaning the rims is meths ok? Or white spirit? Or a general de-greaser spray?
I think I'll leave dismantling the brakes as a last resort, mainly as I can't see how to do so easily. Although nice to see more details on it (cheers Colin). I came across a post a couple of years ago where you mentioned it.

I've put the original (ie XT brakes) back on the bike. With the KoolStop black compound. I'll maybe try some other designs of pads and see how they work (more cost :/). And I'll clean down the rims during the week. Ad finally I'll keep running them, see if I can bed them in.

Here are my v's btw. I think they're a generation newer than your ones colin.
Image
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Squealing v-brakes, help!

Post by Brucey »

those XT ones are the original (first) parallel push version that was part of the 8s XT group. Colin's are newer ones with much improved linkages and bushings in them (as on the 9s group). (But they can still squeal)

If yours have done many miles they will be worn on the linkage and on pad swivel bushing. If the grub screw has come loose the pad swivel bushing can be moving about too. I have used those brakes and they have been prone to squeal, rattling on the loose linkages and many other horrors.

I am still running some of those brakes and I have had to fit anti-chatter springs to them otherwise the rattling drives me berserk. They don't squeal at present though. And I have adopted the reverse strategy from Colin, i.e. my brake shoes are placed behind the brake arms. In theory this should give more uniform pad loading and therefore wear.

BTW PTFE tape is not the same thing at all as scotch tape, and since those brakes have integral pivots you can't easily add it anyway.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
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531colin
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Re: Squealing v-brakes, help!

Post by 531colin »

Its all a bit puzzling.....I don't like it when Brucey does the opposite thing in order to get the same result...... :?

Image

This might help....its my un-modified rear brake, and you can see the parallel push linkage is sort of doubled up like a parallelogram....its here in deepest Shimano.....http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/BR/EV-BR-M750-1792_v1_m56577569830611889.pdf
To take it to bits, I filed off the head of the pivot pin next to the mounting bolt, then you can press it out, undo the grub screw and take the linkage off the arm. I re-assembled mine with a spacer over the pin that pokes into the frame boss (to set the spring tension) so the (now headless) pin can't come out.
Brucey
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Re: Squealing v-brakes, help!

Post by Brucey »

I'm as confused as anything too.

Having said that, my back brake is similar to yours in fact; although I've got as asymmetric a pad as I could find in there, I think that the pad centre is actually slightly ahead of the brake pivot still rather than actually behind as I'd otherwise prefer. However the front pad centre is set well behind the pivot.

Thinking about it perhaps the newer XT brake is actually stiff enough to stop the pad from twisting (about a vertical axis). This is certainly not the case in the same way with my older brakes, because the pivots are so worn. IIRC (and I'll check to be sure) the front pads wear more evenly than the rears in my case presumably because of the twisting. I have the newer XT brakes on another bike BTW so I have a comparison there too.

A similar consideration makes me wonder about toe settings on the OP's brakes; if setting toe in you have to take the slack out of the pivots when you set it, else you've not done much.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
bealer
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Joined: 1 Apr 2010, 1:16pm

Re: Squealing v-brakes, help!

Post by bealer »

Wow, lots of great info their guys. Ah ok, so mine are actually the older ones, argh :/

They don't rattle (yet). Given the LX non-parallel brakes I tried, and the RX5 mini's both squealed, I'll try some other pads and clean the rims first.

And if that doesn't work then maybe I'll dismantle them, and if that doesn't work, it'll either be a new set of v's or disc brakes!
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CREPELLO
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Re: Squealing v-brakes, help!

Post by CREPELLO »

Those rims look awfully shiny. Does the bike see much rain? I find too much dry weather causes glazing of braking surfaces, whereas a good dose of the wet stuff can calm shouty brakes down...sometimes
LuckyLuke
Posts: 374
Joined: 10 Jun 2010, 11:54am

Re: Squealing v-brakes, help!

Post by LuckyLuke »

Hi,

I suffered from squealing V brakes until recently.
I think it was Brucey in another thread who suggested changing to pads which have the pad mounting bolt towards the front of the pad, rather than the middle.

tektro-v-brake-pads.jpg
tektro-v-brake-pads.jpg (10.37 KiB) Viewed 9608 times


V brake pads.jpg
V brake pads.jpg (4.83 KiB) Viewed 9608 times


I used the same pad inner - Kool stop, so the only variable was the pad mounting bolt. It worked! (Don't ask me how! Cheers Brucey BTW.)

Edited for a spelling mistake.
bealer
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Joined: 1 Apr 2010, 1:16pm

Re: Squealing v-brakes, help!

Post by bealer »

CREPELLO wrote:Those rims look awfully shiny. Does the bike see much rain? I find too much dry weather causes glazing of braking surfaces, whereas a good dose of the wet stuff can calm shouty brakes down...sometimes


I scrubbed them clean the other day with soap and water, then used rubbing alcohol to wipe them clean. They were quite blackened before.

Ah intereting. I've got some Tektro pads and shoes with the bolt in the middle I might try just to see how they differ. Aside from that my XT shoes have the bolt towards the front as you mentioned.
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