V-brakes or center pull brakes press directly on the rim to stop the bike. Dirt or grease on the rims can interfere with the brake friction and cause squealing. Wipe off obvious dirt with a clean cloth.
 Rubbing alcohol, acetone, or another oil-free solvent are ideal for removing grease. Wet a cloth in one of these substances, then scrub away grease on the rims.


Warm soapy water isn't ideal, but usually does the trick.
 A wet surface has less friction, so dry it with a clean cloth or paper towel. Handle the wheel by the spokes, not the rims, to avoid transferring oil from your hands. (This is a good tip to follow in daily use as well.)

, Occasionally, a sharp object or a fragment of metal embeds itself in a rim brake pad. Inspect the pads carefully and pick out any foreign objects with an awl or other sharp tool.


If the brake pads are worn thin, you may need to replace them. Typically, there should be at least 1⁄4 inch (0.6 cm) of rubber between the clamp and the tire when the caliper is engaged to brake the bike. You can use a brake pad gauge to measure this precisely.
 New brake pads have a hard surface that needs to be worn in. This will happen naturally over time, but you can shortcut it with a light sanding. If your rims are especially smooth and shiny, scuff them up a little as well.
 You'll have less noise and better braking ability if the pads are angled inward. Looking down from above the wheel, the front of the brake pads should be slightly closer to the rim. Most rim brakes allow you to adjust the angle by tightening or loosening nuts, and/or rotating washers.Never bend the arms of the brake pads to adjust the angle. This will weaken the metal.If your bike doesn't allow for this adjustment, consider replacing the brakes.
Wipe the rim with a dry cloth.
Clean off grime.
Dry the rims.
Check the brake pads for damage.
Sand the brake pads or rims.
Toe in the brake pads.
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