Bicycle Mechanics - Front wheel rim surface is scraped, what to do?
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08-22-11, 07:53 AM
I purchased an 09 Fuji Roubaix Pro off CL for a pretty good price a couple of weeks ago. Last night I took it for its first spin and noticed the front brake was making a "sschh" sound every rotation. I noticed two things - first, that the brakepad was covered in little aluminum bits, and second, that the braking surface on the rim had a pretty large gouge. I tried to take some pictures, which didn't really come out so clear:
Would I be sacrificing the rim integrity if I took some sandpaper to the rim and tried to smooth it out? It doesn't seem to impact the braking abilities of the front brake but I try not to use it if I don't have to due to the scraping. Can I buff this out, or do I have to get a new front wheel?
I was planning on running to Performance tomorrow afternoon (Tuesday) to pick up a Forte Titan front for hopefully $60 (their online price) plus the 10% discount, but I'm a little bit concerned about the spoke count, since I'm a little heavier at 170lbs. I just don't want to shell out cash on a new front rim if I can save this one.
08-22-11, 08:03 AM
I think you'll be alright sandpapering it. When I went into the LBS for advice on how to fix the squealing in my front brake, they told me something had contaminated the braking surface, and thus I needed to sandpaper it with like 300grit. Don't take my advice though. I don't want to be responsible for any damage. Wait for someone else who knows a bit more about this.
Oh and BTW I have alloy rims with machined brake surfaces.
08-22-11, 08:10 AM
It's fine. Run a little fine sandpaper in the direction of rotation to smooth it out and get rid of any burrs or sharp spots.
08-22-11, 08:36 AM
Ikarios: Sandpaper should work fine. Just move it the same way the brake pad travels; you might wrap the paper around the pad and use the pad like a sanding block. Just remove the minimum amount to quiet it down, the pads will take care of the rest with use. You should also sand the pad surface lightly after picking the larger aluminum pieces off.
I dunno - its a pretty good picture if you ask me.
Sandpaper is optional, but the first thing you need to do is clean out the brake pads. They're like a tool, and the bike rim is a part on a lathe, and the grit and aluminum is eating that rim up.
(Koolstop Salmon pads don't do this on my bikes. Replacing whatever you've got with harder brake pads, so they don't pick up the rocks and sand, would be a very good second step.)
Finally, since you're getting the grinding sound once per rotation, I'd bet your wheel is out of true. It can be fixed, or you can just go ahead and replace it.
08-22-11, 09:08 AM
Was going to say to make sure you replace your brake pads, but looks like I was beat to it. Don't just clean them out, replace them. Shouldn't be too expensive.
08-22-11, 09:12 AM
The wheel looks like it's true, when spun in reference to the brake pads. I picked as much Alu out of the pads as I could the first time I took off the wheel but I'll probably have to do it again when I go ahead and sand down the rim. The grinding sound was due to the gouged-out rim - it's a bit deeper than it looks in the picture but I should be able to sand down the peaks of the gouges; hopefully the valleys will not cause issues with the pad.
Thanks for the advice everyone - I'll see if I can't fix it up with some 200-600 grit sandpaper. I was planning on getting replacement Kool-Stop salmon cartridge pads but I think I will wait until I have to replace the front wheel altogether or I run the current Tektro brake pads into the ground. They seem to work fine as they are, so no sense in replacing something that works.
Don't sand the rim down to the low spot. That will simply shorten the life of the rim. It might also make a slightly thinner zone and cause your brakes to pulse.
If there's a raised edge or burr, sand that down flush to the rim, so the brake shoe can simply ski over the scratch. Years ago rims used to be uniformly scored (radially) in an effort to improve wet braking. I don't know if it made any difference other than increasing shoe wear a bit, and it's since gone out of fashion. Your shoes will ski over the scratch with no problem, the scratches will not affect performance in any way.
BTW- don't forget to remove the wheel, and use a file to clean up the surface of the shoes, and remove the embedded bits. You could do this off the bike if you prefer, but on the bike it's a quick easy job.
08-22-11, 05:55 PM
I was planning on getting replacement Kool-Stop salmon cartridge pads but I think I will wait until I have to replace the front wheel altogether or I run the current Tektro brake pads into the ground. They seem to work fine as they are, so no sense in replacing something that works.
IME, it's usually the pads that cause the aluminum to flake off into the pad. Koolstops in either color have always stopped this for me. Other brands might too, but I haven't tried others.
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