Set Up A Bike’s Cantilever Wheel Rim Brake
Prepare The Bosses And Bolts
Clean the threads on the inside of the bosses and the matching threads on the cantilever brake bolts. If they’ve been used before, acetone is the best substance to remove old thread-lock glue. Handle acetone with care it’s volatile and flammable. The inside of the bosses need to ‘sticky’.
Clean the outsides of the bosses. The outside of the bosses need to be ‘slippery’.
Grease Cantilever brake bosses
Lightly grease the outside of the bosses. Don’t get grease the on threads inside the bosses.
Each arm has it’s own return spring. One end of the spring sticks out of the back of the arm and locates in a plate at the base of the boss. If the boss has three holes make sure the springs on each side are located in matching holes. The top hole gives a sharper return action. The bottom hole makes the cantilever brakes easier to pull on, but in this position they return with less force.
Bolt On The Arms
Mount the arms on the bosses with the springs in matching holes. Carefully apply a small amount of thread lock adhesive to the inside of the bosses and then screw in the bolts to lock the arms on the frame. The bolts need to be as tight as possible but still allow the arms to pivot.
If the wheel is out of the bike, replace the wheel. Mount the blocks symmetrically so both hit the rims flat. Check for symmetry with your head on the bike’s centre line. Some systems allow you to toe-in the cantilever brake blocks. If the front of the shoe hits the rim slightly sooner than the back the cantilever brakes may be less likely to squeal.
Set-up the main cantilever brake cable. Thread the yoke onto the main cable and clamp it in a position where the straddle wire will rest in the yoke angled roughly 45 degrees above horizontal.
Open the barrel adjuster a millimetre or two before setting up the straddle wire, then if you set the blocks too close to the rim you’ve got a little bit of wriggle room to play with.
Purpose-made straddle wires have over sized nipples to simplify opening and closing the cantilever brake. In practice, the nipple-end of any cantilever brake cable will do the job.
Set-up The Straddle Cable
Hook the nipple end of the straddle cable into one arm. Run the straddle cable over the yoke and thread it under the cable clamp. Pull the straddle cable through while holding the cantilever brake arms in the ready position with the blocks close to the rim. Clamp the cable.
Balance The Arms
One or both of the arms may have a small screw to adjust the pre-load on the spring. Screwing in the balance screw makes the arm it’s in more active. Unscrewing the balance screw makes the spring work more gently. Adjust the screw – or screws – until both arms move the same amount.
Cut and cap the ends of the main cable and the straddle cable leaving plenty of room for adjustment.
Take the bike for a ride then fine tune the position of the yoke and the length of the straddle wire if necessary. If the lever travels too far lengthen the straddle wire and move the yoke towards the lever. If the cantilever brake comes on too sharply shorten the straddle wire and move the yoke towards the cantilever brake.