V brake squeal

By Andy Blance 12/07/2006.

Brake squeal is phenomenally irritating... I loathe it too!
There are several causes of brake squeal, many of which can be dismissed as inapplicable in your case.
This leaves us with 3 possibilities:-
[1] New rims and blocks often squeal until they have had their surface imperfections worn smooth and the brake blocks have worn to be flat... the problem is greater when both rims and blocks are new… the "problem" will go away with a little use... I'd suggest going down a long hill with the brakes on and give each brake a real squeeze whenever you have sufficient momentum.
[2] Dirty rims/blocks can sometimes squeal for a short time... if the problem does not go away, or if there is petroleum-based contamination, I'd consider giving them a good scrub with some detergent... ironically this may make the squealing worse for a moment. I usually clean my rims by rubbing them with a clean dry rag.
[3] The brakes blocks have not been set up with a small toe in.
We are usually very careful to do this but the mechanic may have got it wrong. With the bosses in front of the fork, if there is any degree of toe out the brakes will continue to squeal indefinitely. But if you have bosses on the back of the fork, the brakes will automatically toe themselves in with wear... if you can see any significant toe out (that is the rear of the block making first contact with the rim) then the mechanic has not done their job properly and you will need to toe the brakes in… the time taken to do this varies from a few seconds to considerably longer.
The method I use is to loosen one shoe off and insert a very thin bit of card at the very back of the block… then I squeeze the lever really hard and tighten the shoe up. I repeat the process on the other side. The things to watch for are:-
(1) That the card does not drop out… if it does you will have perfected a method for reliably toeing out the brakes!
(2) That the card is only at the very back of the block… ditto above.
(3) That the shoes do not drop down in their slot… otherwise you will miss the braking surface.
(4) That you don’t push the shoes up in their slot… otherwise you’ll wear the side wall of the tyre.
(5) That the shoes follow the curve of the rim.
(6) That you always check everything you have done before you ride the bike.


I hope that this helps… I‘d try [1] first…unless [2] and [3] seem more applicable!