Bike Repair – Curing Squealing Rim Brakes

Curing Squealing Rim Brakes

Squealing brakes are annoying at the best of times. When you’re out on a group ride they can be downright embarrassing. Here’s how to cure them.

Even pros get plagued by screeching brakes once in a while. We’ve all been there. The shame of it, with packed pavements stopping to stare at you and riding friends preferring to keep their distance, is enough to make you avoid using your brakes altogether. Of course, that isn’t really a sustainable solution to the problem. Help is at hand though. It’s all about being methodical and running through a sequence of settings. By a patient process of adjustment, testing, and elimination, you should arrive at a positive result and enjoy silent braking again.

The following tips will hopefully explain and illustrate some of the principles involved for the three main types of brakes commonly seen. The most important principle affecting noise is the angle of the pad relative to the rim: generally, the front must come into contact before the rear – known as ‘toe-in’. Correctly toed-in brakes should be beautifully squeal free.

Clean-up act

If your pads still have a fair bit of material, then you’ll need to clean them first. Wipe them off with a bit of damp cloth and check the wear indicator, usually a line about 2mm from the backing edge, marked ‘wear line’. If they’re worn beyond this mark then you should replace them.

The pad will sometimes have developed a ridge along either the lower edge, which indicates that it’s set too low, or the upper edge, which could indicate it’s too high and risks wearing through the tyre over time. Using a coarse half round file or emery cloth, roughen up the surface, making sure to remove all signs of shiny hard glaze. Remove the pad first to improve access if required.

Rim in trim

The condition of the rim surface can have a great effect on braking and noise levels. Most rims now have a machined or heavily scored surface when new. This has gone a long way to reducing the need for masses of toe-in, but as this rough surface becomes re-polished, squealing can occur. Not only can pads get glazed, but so can rim surfaces. Removing bits and pieces of embedded aluminium will keep the scraping noise down; you might have noticed little raised dots of metal which form through braking and deposit themselves on both the rim and pads. Use a Mavic abrasive rubber block or coarse emery cloth and wipe clean. Carefully remove embedded aluminium from the pads.

Pad points

Concave and convex washers provide rotational adjustment in all planes, and are included on many aftermarket pads which can be fitted to side pulls, dual pivots, V-brakes and cantis. Manufacturer Kool-Stop popularised offset pads, which were orientated in such a way that more force was exerted at the front of the pad than the rear, minimising the need for substantial amounts of toe-in while simultaneously curing squashy brakes and squealing. In the late ’80s, Shimano introduced offset pads orientated with the long edge forward. Where possible, short edge forward is less prone to noise, but be sure the closed end of the metal pad holders is always pointing forward.

Snug and secure

First tighten the main fixing bolt to ensure the calliper is firmly attached to the frame. This will be a 6mm recessed nut with a 5mm Allen head, or an older style non-recessed 10mm hex head, preferably a nylock nut (with a nylon insert to prevent the nut working loose). Using a brake spanner or cone wrench on the back adjuster nut, release the front lock nut and tighten the adjuster nut enough that the arms don’t deflect under braking loads, while still moving freely and allowing snappy lever return. Re-tighten the lock nut. Some dual-pivot brakes have an exposed pivot bolt – it’s usually a 4 or 5mm Allen. Tighten firmly while retaining movement.

Side pull toe-in

With the advent of concave/convex washer systems, toe-in adjustment achieved by bending the calliper arms has become pretty much obsolete, but among bikes being dusted off and taken out of the shed there’ll be a few skinny Weinmann side pulls getting a second chance at glory. Bend the arm inward at the front – we used a Park tool that’s now discontinued, but you could use a small adjustable spanner positioned to grab the arm in a similar way. On current dual-pivot brakes – the modern ones – you’ll often get a set of concave/convex washers making toe-in easy; if yours are slightly older and don’t have them, install some that do. Tighten pads firmly so they can’t be moved or twisted by hand.

Baggy pivots

Minimising flex and vibration is the main goal of this anti-noise exercise, so checking that the pivot mechanisms and bolts are tight is critical. V-brakes and cantis are attached to the frame posts using a 6mm bolt, usually Allen but occasionally with a 10mm standard head. The brake arm either rotates directly on this pivot using a brass bushing on older cantilevers, or incorporates an integrated pivot system which displaces wear from the frame post to its own internal mechanism, shared by modern Vs and cantis. This will also include a spring and adjustment screw, which add mechanical complexity and wear possibilities. Replace if the arms are really baggy, and/or if any toe-in of over about 3mm is lost through play in the arm.

V-brakes

Toeing-in V-brake pads will require, in most cases, a 5mm Allen key. In some instances, the pad will use a nut on which you can use a 10mm Y-wrench; it will often incorporate an internal 5 or 6mm Allen fitting. One technique suggested by some of the pad manufacturers for setting toe-in is to insert a small piece of folded card between the trailing end of the pad and the rim. This will keep the rear part of the pad further away as you tighten the nut, and can be useful if you’re having trouble holding the pad in place by hand. Having the spring unhooked on both sides can also make life easier when positioning pads. Bring the pads against the rim to check they’re the correct height, then tighten.

Canti correcting

If your cantilever brakes have an external return spring then it can be easier to position the pads if you unhook the spring first; the arm won’t then fight you as you’re trying to line up the pad against the rim, and fine tuning will be easier. To toe in the pad use a 10mm spanner to immobilize the brake pad mount, then loosen the front nut using a 5 or 6mm Allen key. Some designs reverse this configuration or even require two 10mm spanners. When setting up the pads, leave roughly a 2mm gap at the back of the pad. If the pad keeps moving back into its previous position, try rotating the washers and clamping the pad either a little higher up or down the arm, to avoid the old marks left by the previous setting.

Swap brake type

Cantilever brakes can be tricky to silence, especially on skinny steel touring forks which are more prone to flexing. One thing that doesn’t help is a design that favors noisemaking, where the brake pad post clamp sits way out in front, forward of the arm and mount. If you’ve tried everything to stop the squealing and still no joy, you might have to resort to a different design altogether. One to consider would be the inboard type pictured here, which seems to squeal less; both Ritchey and Avid offer this more compact design. Compare the forward type pictured in step 8 with the rear mount design pictured above, which minimizes flex in the brake arm, reducing the likelihood of high frequency vibration.

Share on facebook
Facebook
Share on twitter
Twitter
Share on linkedin
LinkedIn
Share on pinterest
Pinterest
Share on whatsapp
WhatsApp

Leave a Comment

Your email address will not be published.

Cyclist riding on a road in Vietnam.

Ride in Vietnam

Even at its narrowest point, just 50 kilometers across, Vietnam is an extraordinary place to