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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 06-11-07, 07:25 AM   #1
Redpath
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Rim Dents

Went across a nasty set of RR tracks Saturday going a little too fast-maybe a lot too fast. The impact was pretty hard but the only clue was one of our waterbottles sailing through the air. We stopped to retrieve the bottle and then noticed the rear tire was flat. Actually I thought they both should have been flat so I wasn't all that upset-I only had one tube. Changed the tube, gave the wheel a spin-still pretty true-and finished our ride. Back home I checked the wheel a bit closer and sure enough there was a small dent in the rim. The impact had caused a small depression in the braking surface and had pushed the tire bead lip inwards toward the valley. It was more from the side of the rim than on the circumference. I took a wood block and hammer and got the dent knocked out as best I could from the inside then worked a bit on the braking surface tapping lightly with a smooth face hammer to knock down as many of the high spots as I could. Then I took some fine sandpaper on a woodblock and lightly sanded the area to to get it as flat as possible. The wheel trued up nice and the brakes seem as smooth as ever but you can still feel it with your fingers and if you know where to look you can just see it. This is about as good as I could do with my favorite adjusting tool-my trusty 16oz hammer and nearest scrap of hardwood.

I was wondering how others handled these things. Is there a preferred technique for bumping rim dents?
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Old 06-11-07, 08:00 AM   #2
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if the dent was outward instead of inward.. there is a special tool. It is hard to get them really good. The other option is of course replacing the wheel. I have trashed wheels on tracks before also. : (
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Old 06-11-07, 08:48 AM   #3
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This happened to me last week - but i have been to busy to "fix" it. Am I in trouble for continuing to ride? I just got these rims from Peter White and really don't want to get another.
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Old 06-11-07, 12:10 PM   #4
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Watch the wheel to see if it stays true. If it does, I'd say you're likely fine.

If the wheel is true and the spoke tensions are relatively even, I wouldn't worry about it too much.
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Old 06-11-07, 12:40 PM   #5
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Thanks Jinker. Ill check it out tonight.
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Old 06-11-07, 02:04 PM   #6
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Quote:
Originally Posted by Redpath
I was wondering how others handled these things. Is there a preferred technique for bumping rim dents?
The one thing I always look for relative to "can it be saved" is radial true / roundness or flat spotting. If the spokes sitting directly adjacent to the the point of impact are loose or significantly alter the lateral trueness / side-to-side run-out of the wheel with even minor adjustments it's a pretty good bet that the rim has been permanently deformed. While it's possible to get the wheel laterally true, if the rim isn't replaced chances are you'll eventually find that your wheel will not stay in true and/or will be plagued with spoke breakage and unusual tire wear from the out-of-round condition.

As for fixing bent sidewalls where the rim was flat spotted, been there and done that. If you have either the correct tools or are really careful you can sometimes save a rim. However, the other thing to look at carefully when evaluating if a damaged clincher rim can be salvaged both before and after any repair efforts is the integrity of the rim's hook bead: the upside-down "L's" on the right hand illustration below.



If the impact damage or a repair method deforms either one of the rim's two hook beads I would replace the rim. Given that it's those small lips that keep your tire on the rim, you really don't want them to have any flat spots or other defects. Of the 3 rims I've replaced in the past 5 years, two were discarded for questionable hook beads whereas only one was discarded for a slight flat spot that was taking a toll on tire life. If I think of it, I'll take some photos as I'm pretty sure I still have the rims hanging from a hook somewhere in the garage.
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Old 06-11-07, 08:46 PM   #7
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"Flying'" over trax is not a good practice, as you found out. Neither is "flying" over cattle guards if you live out west.
Once on single racing bike with some downhill momentum in a competitive situation, 'jumped' a cattle guard, rather than slowing. Ah, to be young and foolish again!? Naaaaah!!!
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