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Thursday, April 30, 2009

Brake Levers

BRAKE LEVER TERMINOLOGY

Adjusting Barrel - A hollow screw used to change the length of the brake inner wire.

Barrel Locknut - A nut that holds the adjusting barrel in place.

Brake Caliper - A mechanism which when closed squeezes the rim of the wheel and stops forward/backward momentum.

Brake Lever - A lever that controls the brake calipers via the brake cable.

Cable Anchor - The part which holds the lever arm down, often a socket or a pivoting mechanism attached to the lever arm.

Cable Housing - The outer sheath of the brake cable, designed to be flexible and prevent rusting of cables.

Cast Clamp - A portion of the lever which bends around the handlebar and clamps in place with one or two bolts. See also Pull-Up Strap.

Ferrule (or End Cap) - Fittings that attach to the cable so it fits into the socket or adjusting barrel.

Inner Wire - The interior wire of brake cables, which travels from the lever arm to the brakes.

Lever Arm - The lever parallel to the handlebar which when pulled activates the brakes via the brake cable.

Lever Body - The surrounding exoskeleton of the brake levers that hold it in place and are attached to the handlebars via the cast clamp.

Lever Pivot & Bolt - A shaft-shaped pivot and bolt on which the lever arm rests.

Mounting Bolt - A bolt used to tighten the cast clamp.

Pivot Bushing - A plastic bushing between the lever arm and the pivot bolt.

Pivot Stud - An unthreaded pivot the slides/presses into the lever body.

Pull-Up Bolt - A bolt that holds the lever body to the pull-up strap.

Pull-Up Nut - Goes on the pull-up bolt.

Pull-Up Strap - A flexible steel strap affixed to the handlebar and lever body, an alternative to the cast clamp.

Strap Clamp - Similar to a Cast Clamp, but commonly found on BMX/freestyle bikes or classic 3-speeds and made of flexible metal.

WHEN TO REPLACE BRAKE LEVERS

#1. Bent brake levers.
#2. Cracked brake levers.
#3. Stripped threads on the mounting bolts.
#4. Excessive looseness that cannot be removed by adjusting or replacing the pivot bushings.

WHEN TO SERVICE BRAKE LEVERS / REPLACE PARTS

#1. Levers jerk or move slowly because of dirt build up/lack of lubrication.
#2. Brake cables/cable anchors squeak due to lack of lubrication.
#3. Bent adjusting barrels should be replaced.
#4. Sticky lever pivot may mean a bent pivot should be replaced.
#5. If the brake levers on a horizontal handlebar aren't at a 45 degree angle to the ground, readjust the brake levers to 45 degrees so they can be more easily reached without wrist contortion.

WHAT TO WATCH OUT FOR IN BRAKE LEVERS

Different sized handlebars - Record the size of your handlebars when looking to replace brake levers so you get a size that is compatible.

Derailleur controls too close - Sometimes manufacturers mount the derailleur controls really close to the brake levers, which depending on the type may interfere with your ability to quickly service/replace the brake levers.

Brake Caliper compatibility - Some brake levers don't work with different braking systems due to the distance between the pivot and the cable anchor. When replacing brake levers check to make sure the distance between the two is similar or identical. You will need to adjust the brakes to make sure the brake cables are taut enough.

Pull-Up Strap failure - If there is too much slack the pull-up nut will slip, and the brakes will become very loose or even fall off. The strap may be damaged and if so needs to be replaced. Straps that are bent or cracked may not be immediately seen until after you've taken the brake levers off the bike. The threads on the nut/bolt may also be stripped and will need to be re-cut using a Tap and Die set.

Insecure levers - This means the brake levers either don't fit the handlebars, or one of the parts is broken. A third possibility, less often, is when the lever body is made of cheap plastic and is just slipping constantly because it can't grip the chrome handlebars. In this latter case the plastic brake levers should be replaced with metal brake levers.

DROP-BAR BRAKE LEVERS

Because of their more unusual dimensions and shapes, drop bar brake levers come in a variety of sizes. To determine the proper size measure to the nearest mm at the end of the handlebars at its widest point using a caliper. DO NOT MEASURE A CURVED PART!

If you are using pull-up straps, don't measure them (because they are flexible anyway). Any reputable company will have them marked with a size in mm. If you bought cheap-up straps you will have to measure using trial and error.

REMEMBER TO LUBRICATE!!!

Oil both sides of the lever pivots, the cable anchor pivots and use bicycle grease on the adjusting barrel threads so they don't rust. DO NOT USE CHEAP OIL OR GREASE because they will wash out easily or collect dirt.

BMX BRAKE LEVERS

Should be placed at 25 to 30 degrees below horizontal (ignore the 45 degrees mentioned above). Torque the bolts to 25-35 in-lbs.

UPRIGHT-BAR BRAKE LEVERS

Install at a 15 to 30 degree angle below the grip. Torque the pull-up strap bolt 60-70 in-lbs. If using a clamp instead, torque the bolt to 25-35 in-lbs.

COMPATIBILITY OF BRAKE LEVERS

Depending on whether you are using cantilever brakes, U-brakes, side-pull brakes, dual pivot brakes, disc-brakes or MTB linear-pull brakes there will be different pull ratios for the levers. Measure the amount of movement required to determine whether it is a high or low ratio. Record it in mm.

25 mm or less is for cantilever brakes, U-brakes, side-pull brakes or dual pivot brakes.

30 mm or more is for disc brakes or MTB linear-pull brakes.

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