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This brake was installed on a fixed-gear that did not come with any brakes. The nut on one side rubs against the fork, and over time it rotates and presses the pad against the wheel.

Here is where it is rubbing:close up of problem

The workaround is to unscrew the break and re-center it, but it wiggles its way back and I'd rather a more permanent solution.

The first thing that occurs to me is to put a washer on the bolt between the brake and the fork, but the bolt is just barely long enough to screw into the nut. Could I get a washer and a longer nut to handle this? Would that fix the problem?

The other idea I had was to file down the nut in the photo so it doesn't contact the fork, but that just feels like a bad idea.

[Edit] As requested, here's a shot that shows the whole brake: whole brake

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Can we get another picture from a bit further away? –  Daniel R Hicks Sep 4 '11 at 18:38
    
Was this fork 'pre-drilled' for the brake, and do the pads align perpendicular to the rim? –  ʍǝɥʇɐɯ Sep 4 '11 at 21:31
    
@ʍǝɥʇɐɯ It was pre-drilled. Not sure to the second part, the pad adjustment hole is a little off perpendicular, 10-20deg (eyeballed) away from the fork. It looks just like your diagram. –  joeshmo Sep 4 '11 at 23:12

3 Answers 3

up vote 2 down vote accepted

@Adam Rice is almost there, diagram and suggestion included for what to do now...

First, you need a curved 18mm diameter washer between the brake and the fork. Your brake is a Shimano clone, here is how the original Shimano drive works out:

enter image description here

Note that there is no serrated washer between the curved washer and the brake.

Secondly, you need a 27mm long pivot nut on the back. If your existing nut is 18mm then that is a front nut too, but not suited for your fork. If the nut is 12.5mm or shorter then it is for the back brake.

What now?

Visit your local bike shop on a quieter day of the week and ask for help from the workshop with your predicament. Either get the bike booked in (and expect to pay their minimum workshop time booking slot) or buy the 18mm washer + 27mm nut and do it yourself.

All bike shops have a drawer full of such parts, they may charge ~50p per nut/bolt/washer which is not representative of the cost of the bit or their time to find it for you.

If you are buying something else, e.g. treat yourself to a new track pump, then they may be more helpful and do you the washer/nut out of good will.

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  • Typically there will be a serrated washer between the brake arms and the fork to prevent the brake mech from rotating. I can't tell if you've got one installed, but if you don't, you should. It's hard to tell from the picture you've posted, but I think there should be more separation between the brake arms and the fork, regardless.

  • Front brakes and rear brakes are different in that the mounting screw is much shorter on rear brakes, and so is the recessed nut. Is it possible you're mounting a rear brake in front? That would account for the limited stack-height capacity you've got on that brake.

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There is no washer on there now, I think I will add one and see if that helps. As for the second point, it was installed professionally, so I don't know. –  joeshmo Sep 4 '11 at 20:26
    
Re: point 2 - The bolt should be ~5cm long for the front and ~3.5cm for the back. –  ʍǝɥʇɐɯ Sep 4 '11 at 21:21

Your caliper should stay reasonably well-centered. Are you certain that all the nuts and washers are in place to allow you to adjust the position of the brake with a thin brake wrench and then tighten the the other two nuts to keep everything in place?

Other than that, a track fork really isn't designed for a brake. Yes, there is a hole in there for that but it is more of an afterthought than a critical design feature. One can't expect any caliper to fit.

I would consider the following in this order:

  1. Double check all hardware is in place and adjusted properly so it doesn't pivot over time. You might or might not be able to find a longer recessed nut to go into your fork hole and thus allow a spacer washer to position the caliper a little bit further from the fork.

  2. Replace caliper with something that will fit. It looks from the picture that you're using a dual-pivot brake? Sidepulls are a little smaller and might not interfere with the fork.

  3. Replace your track fork with a road fork that can take the brake you need it to take.

I would not file down the interfering nut.

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Hadn't considered replacing the fork, thanks. –  joeshmo Sep 4 '11 at 20:27
2  
Actually replacing the fork is not a totally outrageous idea. The front fork on a track bike has round fork blades, not oval, and for good reason - it is not designed to handle brake forces, just side to side power pedal stroke forces. Although I have never heard of a track fork collapsing because someone has drilled it for a brake, put a brake in and then stopped with it, it could happen... –  ʍǝɥʇɐɯ Sep 4 '11 at 21:25
    
fwiw, it was already drilled. –  joeshmo Sep 4 '11 at 22:39

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