Bicycle Mechanics - Sidepull brake won't return to centre
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05-10-10, 02:17 PM
Just built up an old frame with some fairly old brakes but the front one doesn't seem to return to centre properly.
What can I do to fix this?
Part 1: release the springs from the arms, are they level of the same amount in undeformed shape? If not, bend the spring little by litel until it does.
Part 2: note the third, fixed part that holds the spring? that can be rotated! it has a screw on the other side of the fork, loosen it rotate that piece with the spring more in the direction to correct the problem, then tighten it back
05-10-10, 03:27 PM
Check out this thread: A small issue I've started to notice with my front brake (http://www.bikeforums.net/showthread.php?643706-A-small-issue-I-ve-started-to-notice-with-my-front-brake)
Basically you want to tighten the centrebolt in a way that ensures the nut doesn't spin it:
The upper arrow for the left hand is reversed. The left hand actually pushes down while the right hand pushes up to tighten the rear nut. On a lot of newer brakes, you don't have to loosen the rear nut. Just grab the centrebolt with the wrench in front and spin it so that the pads are equidistant from the rim.
05-10-10, 03:36 PM
Thanks guys, will try that tomorrow.
One other detail, before you center the brake put a drop of oil where the leg of the spring meets the brake arm. As the brake opens and closes the spring slides up and down the arm slightly, and any unbalance in friction can cause one arm to move less than the other, and throw it off center. Do the oil first so you won't have to loosen and recenter anew.
Sometimes cable routing and legnths also affect how the calipers can center themselves while riding. The cable's routing can cause it to push or pull excessivly on the caliper causing it to end up uncentered most of the time specially when steering. Also for brake systems with non-aero, exposed cables at the brake levers, they can be too long as to exert to much downward pressure on one side of a sidepull front caliper just from the weight of the overly long cable casing and cable, causing it to maintain an un-centered position while riding, especially on rough roads, Cable routing and setup can get tricky and it takes a bit of work and experimenting to come up with the best routing and legnths for them so that the calipers will not have centering issues. Also, as the previous posters have noted, make sure that the mounting bolts are tight enough. any loseness on the mounts just makes the centering problem worse.
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