Why do my brakes squeal ?
| Why do my brakes squeal ? |
| Squealing brakes are a sign of one of two things : the friction material is all gone and you’re jamming the backing plate against the brake rotor, or the fit of the brake pad against the caliper piston isn’t as snug as it could be. Either way, the squealing is the result of an extremely high-frequency vibration between the pad, the caliper piston and the brake rotor. Some vehicles have problems with squealy brakes right from the factory. In those cases, simply changing brake pad manufacturer can often cure the problem as the different pads will have a slightly different harmonic frequency, which is harder to attain. A classic example was one of the BMW R1100 touring bikes. From the factory, they’d squeal like crazy, and BMW redesigned the brake calipers and rotors a couple of times until they finally just switched to a different brand of pads and the problem vanished. |
| Solving brake squeal |
| A good way to solve brake squeal is to put some copper-based grease on the back of your brake pads. That’s very important so I’ll say it again in CAPS : THE BACK. Copper grease is extremely resistant to pressure and heat and if you get any on the front of your pads, you’ll need new pads and rotors or discs. The picture here shows a cutaway of a disc brake assembly. The blue caliper housing on the right is missing to show the two silver brake pistons. The idea is that it creates a small pocket of sticky lubrication between the front side of the brake pistons and the back side of the brake pads. This is usually enough to prevent the high-frequency squeal. If you’re not happy doing this yourself (working on a safety-critical part of your car like the brakes isn’t something just everybody should be doing) then ask your friendly local mechanic to do it for you. Whilst copper grease such as Copaslip works well in the short term to solve brake squeal, long-term, it has an adverse affect on the rubber dust seals of the caliper pistons. This can lead to the seal deteriorating or failing completely. If that happens, it leaves the piston and it’s surface exposed to the very elements from which it should be protected. Just so you know. |
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| The other solution to brake squeal |
| Whilst the ultra high frequency vibration is one cause of brake squeal, the other biggie is related to suspension alignment. Driving on badly-maintained roads, mountaineering through pot-holes or kerbing your wheels all make the suspension move around in ways it was never really designed to cope with, and this in turn leads to the suspension bushes becoming stressed. Normally, re-aligning the wheels on a vehicle is corrected by mechanical adjustment only. If the mounting rubbers are not de-stressed first, then it leads to the transfer of the sound generated during braking into the chassis and body which then amplifies it to where we can hear it. Sort of like a giant record player with the suspension as the pickup needle and the entire car as the speaker. If you have squealing brakes that copper grease doesn’t solve, look into a proper suspension realignment and possibly new suspension bushes.Â
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