If you know that nasty, abrasive sound of squeaking brakes that interrupts a nice ride, you know it's dang near unbearable. Not only is the sound of a squealing brake massively annoying, but it can also indicate deteriorating brake performance.
Alleviating this issue is important for any rider, but before one can fix the problem, he or she must first determine what is causing it. There are two primary types of bike brakes: rim brakes and disc brakes. Rim brakes use the caliper to apply stopping force on the outside of the rim itself, while disc brakes move the braking surface off of the rim and onto the rotor.
Here are some ways that cyclists can detect and fix problems related to their squeaky bike brakes:
Before you start taking apart your braking complex, check to make sure that the calipers, the braking surface on the rim, and the brake blocks are cleaned thoroughly and in working order. You can also check for any loose bolts with a torque wrench to ensure that everything is tightened properly. The cause of squeaking brakes can occasionally be as simple as loose parts.
Contamination can also be a factor in having loud, obnoxious brakes. If you're riding in wet conditions, your brakes may collect oily or foreign substances as you go through puddles or whatnot. Remove this issue by de-greasing the rims with a brake cleaner, which you can find online or at any bike shop.
Worn-down brake blocks are also a common cause of squeaky brakes. Over time they can collect grit like sand and gravel, or become glossed over by repetitive usage. To address this problem, get something like a nail file or a sheet of sandpaper and rub off the top layer of the blocks. Dirt can also find its way into the rims, so inspect those thoroughly as well to make sure there is nothing in there jamming up your brakes.
Despite being slightly different in functionality than rim brakes, disc brakes suffer from the same general issues on account of squeakiness. Contaminated rotors and pads are the main culprits, but be cautious when cleaning them with a degreaser. Over-application can wear down the pads and create a nasty squealing sound when you ride. Still take the time to clean them and rid them of any contaminants, but don't put too much degreaser on them while you're at it.
If your pads do become contaminated, you will have to remove them altogether from the bike. Once removed, it's best to use the sandpaper method to rub off the top layer of the damaged pad. If it's too far worn down then you'll have to get a new set of pads.
Another reason for squeaky disc brakes is a misalignment of the caliper and the rotor. The rotors can become bent fairly easily, so check up on them frequently, particularly after a crash or after you have to cram your bike into a tight space like the trunk of your car or a crowded garage.
To realign the caliper and the rotor, first loosen the caliper bolts, then squeeze the brake levers. While the levers are squeezed, tighten the bolts back on and use your best judgment to determine if they're aligned correctly. It may take a few trial and error runs, but it won't take a terribly long time.