Bicycle Mechanics - Problem with rear rim braking surface
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05-18-09, 10:21 PM
New guy here. looking forward to learning lots!
I recently got a great deal on a 2006 Fuji Team Pro. (Mint condition for $500!) Everything is great, however, when braking the rear wheel, I get these "bumps" in my braking.
After checking out the rear wheel, I realized that there is an uneven "seam" on the braking surface where the metal joint is uneven. When this seam gets to the brake, it catches on the pad, making this "bump" during braking.
I had some 600 grit sandpaper and tried sanding down the seam making it less harsh. I took off the jagged edge about 50%.
Is this okay to do, or should I stop and take it to the LBS?
05-19-09, 09:05 AM
Single-wall rim, you can use a crescent wrench covered in electrical tape to do a little splaying work. Less success with double-wall. Sanding helps a little.
It is not uncommon to experience a "tick" on most entry to mid-range alloy rims. In terms of braking performance - things will be pretty much normal. Sometimes it'll wear itself in...
Now if you are getting a serious bump - not just a rub - but a pretty aggressive tick - take it to a shop for a looky. It may just be that the manu really messed up the joint. On very rare occasions, I've pulled a rim out of my stock where the cut ends of the rim came together and were pinned with the ends meeting 1-2mm off to the side of each other. Talk about a nasty tick! It can be enough when dragging brakes to turn a "tick" into a jam on fresh clean cut brake pads.
This is a pinned wheel, nothing wrong with that kind of wheel, I've used them for over 30 years! And even highend pinned wheels could do the same thing your describing.
This is relatively a simple cure, take a fine emery paper attached to a sanding block and simply sand the area where the seam or the tick is on both sides of the rim till it no longer grabs the paper. Next take a 3M ScotchBrite pad and scrub the entire rim on both sides till the sides are shiny.
If you find that the fine emery paper is not strong enough to remove the click, use a 400 grit sand paper to take off more of the bumb, then go back to a medium grit emery paper, then to a fine emery to smooth it out, then to the ScotchBrite.
DO NOT use any tools like a Dremel because you could damage the rim beyond repair.
05-19-09, 02:40 PM
If it's a large step between the seam edges, you need to also feather out the sanding. A file would work better in this case to keep the surface flat. Then so light sanding afterwards to blend the surface textures.
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