Bicycle Network: Bikes 'n' Bits
Take a brake
With the (hopefully) wet weather of winter approaching, it’s time to check your brakes. This article appeared in the April-May 2010 edition of Ride On.
What you need
A good pair of eyes; small file; allen key; rag; detergent for cleaning; isopropyl alcohol.
Grab an allen key that fits the pad binding bolt and take the old one off. Move the new pad into place, remembering to put the washers and adjusting spacers on in the same order as you took them off.
With your index finger supporting it from underneath, manoeuvre the pad into position. There are three things to consider when positioning a rim brake pad:
- Height - The pad must be centered vertically on the rim, between the tyre and bottom of the braking surface. Allowing the pad to ride high may drag it on the tyre, and too low it may only work on half its surface and perhaps dive into the spokes.
- Radius - The curve of the pad must follow the same curve of the rim. If the leading or trailing edge of the pad is high or low, you will experience the same symptoms as above.
- Angle - The full contact face of the pad should come up against the rim. I’m not talking about toe-in here, but the two surfaces contacting squarely. With your spanner, close the anchor bolt or nut down so it is secure. Push the pad up against the rim and inspect it. Does it look centered and flat against the rim? Perfect. If not, have another go. Remember that as you tighten the bolt the pad will want to creep around clockwise. Hold it really firmly with your fingers and you’ll be fine. Repeat the process for all the pads on your bike.
When you’re sure everything is tight and adjusted, re-engage the cable and see how they feel at the lever. If you let the cable anchor bolt off, pull the cable through the desired amount and secure it. Again, check the levers so that both front and back travel equal distance.
When operating the lever, notice that both arms should travel equal distance to the rim. If one travels more or less, an adjustment can be made with a centering screw. If one arm is traveling too far, loosen its centering screw and tighten the screw on the opposing arm. Continue until both arms travel the same distance.
Clean the rims
An often overlooked component when adjusting brakes is the rim itself. A clean rim free from debris and oil will certainly stop you faster than a dirty one. Clean the wheel and especially the rim surface with a good cleaner. Follow up with an inspection of the rim’s braking surface. It should have nice flat sides (concave sides can be dangerous, with rim failure a possibility). Go the extra distance and clean the braking surface with isopropyl alcohol. This will remove any residue left over from the initial clean.
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