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Old 01-14-14, 10:51 AM   #1
kgoings
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Crashed and messed up the braking surface of my rims...replace only rims?

I have 2014 Cannondale SuperSix with RS11 wheels. I dipped my front wheel into a large crack in the pavement today and scratched up both front and rear rims. The braking surface is all scratched and gouged up...braking sounds horrible. The wheels are still true.

I looked and it seems I can buy a wheel set for around $200....could I replace the rims only and get out any cheaper?
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Old 01-14-14, 10:58 AM   #2
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I have 2014 Cannondale SuperSix with RS11 wheels. I dipped my front wheel into a large crack in the pavement today and scratched up both front and rear rims. The braking surface is all scratched and gouged up...braking sounds horrible. The wheels are still true.

I looked and it seems I can buy a wheel set for around $200....could I replace the rims only and get out any cheaper?
Do neither. Use a file to remove the raised edges of the rim, back down to the height of the rest of the track. Leave the cuts and gouges alone. Cuts and nicks don't affect braking, and at one time it was even fashionable to score rims to improving braking. Look at MC discs).

I'm not saying the gouges will help, but they won't hurt either, and you can keep the dough in your pocket.
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Old 01-14-14, 11:02 AM   #3
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You maybe able to smooth the surface with an abrasive, either pad or block, if the rims are too damaged for/after this, would just look at replacing the wheels.

Although you can get some replacement rims for Shimano wheels, for the lower end ones (having had a quick look at the tech docs, and the part No, can't find this rim available as a spare), it's not often cost effective, especially if you have to get a shop to rebuild vs just replacing with a new set.
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Old 01-14-14, 12:35 PM   #4
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Agree with above posts. Removed raised edges but not the base material. Scratches will remain but won't affect braking. Use a flat file, sanding block, or coarse stone.
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Old 01-14-14, 12:53 PM   #5
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What they said...

i used to scuff BMX rims and it definately helped improve braking, did wear out pads quicker though.
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Old 01-14-14, 01:16 PM   #6
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BTW- this is one reason why it's wise to use tires that are wider than the rims. When dropped into slots, the tire acts as a buffer and takes the hit instead of the rim
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Old 01-14-14, 01:57 PM   #7
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BTW- this is one reason why it's wise to use tires that are wider than the rims. When dropped into slots, the tire acts as a buffer and takes the hit instead of the rim
Agreed. I realized this after the fact when I rebuilt a set of wheels with HED C2 rims a year or so ago. It hasn't been a problem since riding the new wheels, but it did give me pause at first. With my 700x23 tires they overhang the C2 rims by maybe a millimeter on each side, barely worth mentioning, but at least it's something.

Incidentally, I recently had a rock jump over and put a ding in my front brake track that made a heck of a noise with each revolution throughout that ride. I went home and wrapped some sandpaper around a small block of wood and smoothed out the high points. The next ride things were as quiet as they had ever been, like the damage never happened.

-Jeremy
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Old 01-14-14, 02:29 PM   #8
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I will try filing it down. Hope it works! Here is a pic of some of the damage.
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Old 01-14-14, 02:55 PM   #9
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I will try filing it down. Hope it works! Here is a pic of some of the damage.
That'll come up fine. If you use a file, you want a 1/2 mill, so you get a smoother finish, otherwise sandpaper on a block will be fine.

Just take off the raised edges, using the base line between them as a guide. You might hear the shoes passing over the cuts for a while, but even that gos away very quickly.

BTW- clealy a case of tire too narrow to protect the rim, go 3mm wider next time around if you want to avoid this.
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Old 01-14-14, 02:57 PM   #10
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That'll come up fine. If you use a file, you want a 1/2 mill, so you get a smoother finish, otherwise sandpaper on a block will be fine.

Just take off the raised edges, using the base line between them as a guide. You might hear the shoes passing over the cuts for a while, but even that gos away very quickly.

BTW- clealy a case of tire too narrow to protect the rim, go 3mm wider next time around if you want to avoid this.
Sorry, but I don't quite understand the bolded statement.
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Old 01-14-14, 02:59 PM   #11
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Sorry, but I don't quite understand the bolded statement.
You can see original rim surace between the gouges. Sand only until you start sanding there, then stop. A perfect job will leave a smooth track with a few sandpaper or file marks on the original surface (not counting the deeper cuts). It's also OK to stop short of perfect and let the shoes finish the job.
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Old 01-14-14, 03:01 PM   #12
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Thanks!
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Old 01-14-14, 03:18 PM   #13
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If the grooves are as deep as they appear in the picture I think you'll need a new rim before long. The process FB has described will probably work well for some time but I'd be looking for a new rim. I think the deeper grooves will shorten the life of the brake pads considerably. But from the photo I think it's hard to make a good judgement.
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Old 01-14-14, 03:21 PM   #14
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If the grooves are as deep as they appear in the picture I think you'll need a new rim before long. The process FB has described will probably work well for some time but I'd be looking for a new rim. I think the deeper grooves will shorten the life of the brake pads considerably. But from the photo I think it's hard to make a good judgement.
Groove depth has little impact on shoe wear, though any grooves will increase wear slightly. However replacing shoes twice as often (if that) is far less expensive then replacing wheels or rims. On the bright side, if shoe wear is increased, it means that the shoe surface will be kept dressed and unglazed.
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Old 01-14-14, 03:27 PM   #15
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+1 on all above. But I'd also cover the interior painted portion with a good layer(s) of masking tape. You'll be seriously pissed at yourself if you scratch up the painted portion fixing the braking surface.
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Old 01-14-14, 03:36 PM   #16
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+1 on all above. But I'd also cover the interior painted portion with a good layer(s) of masking tape. You'll be seriously pissed at yourself if you scratch up the painted portion fixing the braking surface.
One would have to be seriously inept to damage the painted surface since it runs off a a significantly different angle.
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Old 01-14-14, 03:55 PM   #17
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To semi-quote your signature. An ounce of prevention is worth a pound of remorse. Its been my sad experience that when a cutting, scratching, gouging tool slips, it will always slip in the worst most visible spot. Just saying.
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Old 01-14-14, 04:05 PM   #18
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To semi-quote your signature. An ounce of prevention is worth a pound of remorse. Its been my sad experience that when a cutting, scratching, gouging tool slips, it will always slip in the worst most visible spot. Just saying.
I can see that, so it's up to the OP to decide how much he trusts his hand skills. I do this stuff all the time, but my file is too long to slip to the inside.
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Old 01-14-14, 04:44 PM   #19
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A machinist's scraper like this http://www.jlsmithco.com/SCRAPERS/HO...ANDARD-SCRAPER can be used to remove the raised burrs from the brake tracks without removing the undamaged material.
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Old 01-14-14, 05:12 PM   #20
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Groove depth has little impact on shoe wear, though any grooves will increase wear slightly.
My thinking is that some of the shallower and wider grooves will be worked enough by the filing and sanding that the edges will round off and some of the scratches may even disappear. But the edges of the deeper grooves will not be reduced as much by the work. I expect that under hard braking when the brake pads hit the damaged part of the rim there will be a noticeable grabbing effect that may not be equal on both sides of the wheel. I would also be concerned with the deeper grooves weakening the rim enough to cause structural failure. Like I said, from the pictures it's hard to know what to expect. I'm usually in favor of fixing a problem instead of replacing parts. But in this case we're talking about brakes and safety.
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Old 01-14-14, 05:27 PM   #21
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A machinist's scraper like this http://www.jlsmithco.com/SCRAPERS/HO...ANDARD-SCRAPER can be used to remove the raised burrs from the brake tracks without removing the undamaged material.
The OP doesn't have to buy another tool he'll rarely ever use again. Also, those are great on steel, but of not used carefully can cut into and raise burrs on aluminum.

If he's married, he probably doesn't have to buy anything. His wife probably has a few of these someplace. They are perfect fo this job, though the gray stain rims leave might not make the lady happy and you'll need to buy a replacement for a buck.

OTOH- this is a rare opportunity, how often do you get a chance to misuse your wife's tools.

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But the edges of the deeper grooves will not be reduced as much by the work. ....
Experience tells me that it doesn't matter. Shoes lay flat to the rim and span gaps without deflecting into them. In any case if the edge did have the ability to shave shoes, it would break down quickly enough.
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Old 01-14-14, 08:36 PM   #22
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Experience tells me that it doesn't matter. Shoes lay flat to the rim and span gaps without deflecting into them. In any case if the edge did have the ability to shave shoes, it would break down quickly enough.
Experience tells me just the opposite. As I said, under hard braking the pads are pressed into the grooves. It they weren't you would not feel any grabbing or hear any scuffing sound. Anyone who's ridden a surface damaged rim can tell you that at the very least you'll hear a scrapping or scuffing sound when the pads contact the deep scratching or grooves. And depending on how bad they are you'll feel grabbing that can be pretty severe. If those pads stayed completely flat to the braking surface the damage would go by just as smoothly as the rest of the rim.
And as for breaking down, I agree "it's" going to break down quickly enough, and it's the pads that are going to break down because they are softer than the rim.
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Old 01-14-14, 08:49 PM   #23
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Experience tells me just the opposite.
We don't have to debate this. For about a dollar's worth of emery and 5 minutes of his time the OP can do hat he can. Then he can ride the bike and see if the results are acceptable. It's not like we're talking a major investment. Compare to condemning a wheel simply on he assumption that it'll be noisy or shoe wear will be excessive.
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Old 01-14-14, 08:57 PM   #24
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Old 01-14-14, 09:03 PM   #25
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We don't have to debate this. For about a dollar's worth of emery and 5 minutes of his time the OP can do hat he can. Then he can ride the bike and see if the results are acceptable. It's not like we're talking a major investment. Compare to condemning a wheel simply on he assumption that it'll be noisy or shoe wear will be excessive.
I agree 100%. The "debate" started with your post #14 . I never said the OP should not try fixing it.
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