Mechanic Tips of the Trade

How to Maintain Rim Brakes.

4 simple solutions to a finicky adjustment.
If your brakes squealed on your past few rides, one (or all) of these three simple procedures should return you to silent slowing:

Clean the brake pads and rims with an alcohol-based product. Acetone works really well—and clears the sinuses at the same time. Use a scrub pad or file to clear the brake pad of glazed-on gunk. Check to see if the pad is glazed beyond saving: If you can't scratch into it with a fingernail, you need new pads. (While you're down there, check pad thickness: Most pads have wear indicator lines, but if not, use the grooves as your indicator. If they're gone, the pads need to be replaced.

If the first two steps don't stop the squeal, you need to toe-in the
pads—angle them so the front of the pad contacts the rim first. Loosen the bolt holding the pad to the brake arm, position the pad, then lightly tighten. If the pad didn't slip out of position (it often does), finish tightening. Then check the position against the rim. If you're new to this, it will be a painstaking, frustrating, hellish parade of do-overs. Just know that you're not alone.

DON'T OVERDO THE TOE-IN: The rear should have about a millimeter of clearance as the front tip hits. With linear brakes, the difference should be less than a millimeter. If the brakes continue to squeal, toe-in slightly more—but never go beyond 2 millimeters.

Check that your pads fully contact the rim. If any of these coordinates are off, reposition the pad. Always check pad position with a spinning wheel rather than a still one-minor hops in the wheel can sometimes cause a seemingly well-adjusted pad to do bad things.

Vertically, the entire pad should reach the rim at once—not the upper or lower edge first.

The upper edge of the pad shouldn't touch any part of the tire. Sometimes you can hear this (a short, soft rubbing sound) when you can't see it. Make sure what you hear isn't an untrue rim hitting the pad, though.

The lower edge of the pad shouldn't hang off the bottom of the rim. If it does, the pad can slip entirely under the rim and do very bad things to your wheel and body.

If your brake levers bottom out against the bar, you need more cable tension.

Try a minor adjustment by dialing out the barrel adjuster either at the lever (mountain bikes) or down on the brake arm (road bike). On mountain bikes, be sure to retighten the locknut flush against the brake lever to secure the new setting.

If you can't take up enough slack with the barrel adjuster, tighten the cable. First, dial the adjuster barrel all the way in, then back out one full revolution. Next, while holding the brake arms together so the pads contact the rims, loosen the anchor bolt on the brake arm and pull the cable through until it's barely taut. Refasten the anchor bolt. Generally, some slack enters the cable and leaves clearance between the brake pads and rim. You want 1/8 to 3/16 of an inch clearance. If there's too much or too little, readjust the cable tension.

Make sure the brakes are centered—one pad shouldn't be closer to the rim than the other.

Some brakes have a Phillips or hex-head screw that adjusts spring tension on both arms; some on just one arm. If your brakes have two, move the pads with equal (and opposite) adjustments on both sides-in half a turn on one side, out half a turn on the other. Turn the screw clockwise to increase spring tension and move the pad away from the rim; counterclockwise to bring it closer.

Sidepull (road) brakes without a tension screw usually can be adjusted by loosening the mounting bolt, twisting the caliper to center it, then retightening the mounting bolt.

*Before doing any of this, make sure your wheels are true. If there's as much as ¼-inch of space between either brake pad and the rim, and the rim hits the pad when spinning, you need to true your wheel.

FROM NOW ON
Check pads for wear or embedded objects after every wet or muddy ride, or every three to five rides in clean conditions.

Check brake centering quickly before each ride—lift your bike and spin the wheel. This will become an easy habit.

Check brake tension before every ride—just give the levers a squeeze.

You can get all of these handy items at Bikeland.