Here’s how to fix squeaky disc brakes on a mountain bike. The two main causes of squeaky disc brakes are an inadequate break-in (or bed-in) procedure, and excess brake dragging. Incompatible pads and misaligned brake calipers can also contribute to brake squeal. But first, let’s look at how to break or bed-in disc brake pads, then explore some other solutions.
How to break in or bed in disc brake pads on a bike
Disc brake pads and rotors are designed and manufactured in such a way that during operation, the pads deposit a tiny film of pad material onto the rotors. Among other benefits, this enables the brake pads and rotors to work in unison under pressure, without causing squeal.
The break in procedure below is designed to produce that transfer of pad material (undetectable to the human eye) to enable your brakes to operate squeal free. Keep in mind that inadequate pad break-in can lead to inconsistent and imperfect transfer of pad material around both sides of each rotor, causing even brand new brake pads to squeal.
In addition, excessive brake dragging, or too much ‘feathering’ of the brake during your ride, can bring on brake squeal. Feathering the brakes has a negative impact on pad material transfer, leading to an inconsistent film on your rotors and glazing of your rotors. Balance that negative impact of feathering and dragging by performing a decent amount of hard braking during your ride.
The break-in procedure
- Perform 3 to 5 repetitions of high speed bitumen stops, going from about 40kph to zero, without skidding
- In each repetition apply the brakes hard three or four times to come to a complete stop, with a split-second release of the brake levers between each of those three or four pumps of the lever
- Each 40 to zero run should go something like this: 40kph, brake hard for one second, split-second full release of the levers, brake hard for a second, split-second full release, and a third and possibly fourth hard brake to bring you to a complete stop
Super Tips – Troubleshooting other causes of squeaky disc brakes
Pad problems – Are you running full metallic disc brake pads? Although generally offering less bite, organic or semi-metallic pads are usually more forgiving and can operate quieter than full metallic pads, reducing or often even eliminating squeal.
Caliper alignment – Are your calipers aligned properly? Check that your rotors are running dead straight through the calipers, and that the rotor is centered between both brake pads, so that the pads contact the rotor at the same time.
A twisted caliper means that the rear edge of one of the rear pads, or the lower edge of a front pad in the case of the front brake, will be contacting the rotor first, and on an angle. This can be enough to cause the pad to chatter and squeal when anything less than full brake pressure is applied, particularly if your pads haven’t been broken in properly.
Loose nuts – Loose brake caliper mounting bolts or loose rotor mounting bolts or lock rings. One or two bolts only have to be a tiny bit loose to create a huge amount of vibration and noise under pressure. Check all your mounting bolts are tight, but don’t over tighten!
Disc Brake Cleaning Products – Only use mountain bike brake maintenance and cleaning products. Never use products that are only designed for motorbike or cars.
Lubricating – To remove the risk of getting chain oil on your rear rotor, oil your chain by dropping lubricant onto it, rather than spraying lube onto it.
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