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Brake adjustment

Old 10-18-13, 10:55 AM
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TrojanHorse
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Brake adjustment

I noticed that one of my front brake pads was dragging lightly on the rim the other day. I've never noticed it before.

I took a couple photos - I pumped the front brake a few times and you can see the right pad is lightly up against the rim but there's quite a bit of room for the left pad. I thought I could adjust the spring tension (3rd photo) but there's nothing to adjust, the spring appears to float freely in the brake frame.



In the second picture, you can barely see the top of a hex bolt that can be used to center the brake on the rim (Red/Force) and I fiddled with that for a bit - turning it one way appears to actually close the brake arms, and turning it the other seems to loosen up the rotation of the brake frame so that the right pad isn't dragging. Not really though, I just checked again.

Lastly, I'm theorizing that the cable housing might be a skosh long because the housing is pushing down a little on the brake, although turning the bars in either direction doesn't appear to affect anything. I could presumably clamp the brake a bit higher on the cable or just shorten the housing a few mm... it's a jagwire housing and it's fairly stiff.

Any suggestions?
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Old 10-18-13, 11:01 AM
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fietsbob 
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see the flat spot in the last picture ? its on the center bolt ..
loosen the nut on the back of the fork hold a open end wrench on that flat

and then tighten the mounting bolt again, keeping the brake centered holding the wrench on that flat .

its a 2 handed 2 wrench job 1 allen hex 1 Open end..
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Old 10-18-13, 11:09 AM
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there are centering flats next to the fork crown. (centering at about 2:50 of video). http://www.youtube.com/watch?v=3KpcaIZPq9A
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Old 10-18-13, 11:38 AM
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Alright! Thanks, I'll go give that a whirl.
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Old 10-18-13, 11:42 AM
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One thing that plagues single pivot brakes is spring friction at the arms. As the arms move in and out the spring moves up and down slightly, sliding against where it meets the arm. A bit of friction there can cause the arm to open less throwing off the centering when open. So make sure the place where the spring meets the arm is reasonably clean (wiped, not washed), then put a drop or light oil, like a teflon dry lube there.

Now work the brake to make sure it's opening consistently, then center by loosening the mounting nut, rotating the pivot and re-tightening.
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