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Old 05-18-12, 09:36 AM   #1
FastJake
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How to tell if a rim can be re-used before lacing it up?

Bought a wheel for $10. Araya CTL-370 rim laced to a Suntour GPX hub. I know the spoke tension is way off, and some of the spokes have suffered bends. I would like to dismantle this wheel and lace up the rim to a Shimano cassette hub and make a "nice" wheel for myself. But right now, there is a subtle flat spot that I can feel while riding. I'm not sure if this is a result of the bad spoke tension or if the rim is damaged.

Right now I'm using it as a beater SS wheel. So before I tear it apart and leave myself with nothing, will the rim straighten out when I rebuild it with a new hub and spokes? Or should I just keep riding the thing until it dies and buy myself a new rim?
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Old 05-18-12, 09:44 AM   #2
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I'd probably unlace it and see if it's straight without tension. If it is, you have a good chance of a straight wheel when you build it up. Might as well reuse it if there's enough meat in the sides.
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Old 05-18-12, 10:09 AM   #3
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+1 on Scott's suggestion. Unlace it and lay the rim on a flat surface. If it lays flat or can be made flat with out serious effort and there are no major dings or kinks, you can likely reuse it successfully.
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Old 05-18-12, 10:12 AM   #4
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And perhaps you can lay it next to a know good rim to try to identify the flat spot, if it still exists after unlacing.
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Old 05-18-12, 11:25 AM   #5
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And perhaps you can lay it next to a know good rim to try to identify the flat spot, if it still exists after unlacing.
Or roll the rim on a flat surface. If it still has a flat spot when unlaced, the spokes in that area will necessarily be under-tensioned relative to the rest of the wheel if you make the wheel round. Difficult to quantify but that area will be more prone to breaking spokes than the rest of the wheel.
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Old 05-18-12, 11:37 AM   #6
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Nevermind, I found the flat spot and after a closer examination there is a matching ding on both sides of the rim. Ugh, oh well.

Thanks for the advice everyone. I will keep it in mind for future wheels..
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Old 05-18-12, 12:26 PM   #7
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Seems like somebody on BF had made a jig to hold a rim stationary and press/pull on high/low spots to bend them back into true... can't find it now, of course.
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Old 05-18-12, 12:29 PM   #8
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I'm a snob: if I'm going to put the time into building a wheel, I'll almost always opt for a new rim. Unless the rim is something really, really special.
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Old 05-18-12, 12:43 PM   #9
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Seems like somebody on BF had made a jig to hold a rim stationary and press/pull on high/low spots to bend them back into true... can't find it now, of course.
It's called a door-jamb.
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Old 05-18-12, 12:57 PM   #10
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Here we go... requires the wheel to stay laced-up: http://www.bikeforums.net/showthread...=1#post8810573

One could ask whether it's worth it to try rebending the old rim, but if you're already planning on a new rim, you won't be out much if it doesn't work.
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Old 05-18-12, 01:17 PM   #11
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Also a glass coffee table makes a great jig to measure flatness of rim. Lay it on the coffee table and notice the opposing high and low spots. Grab two opposing high-spots and place the low-spots on the edge of a door-jamb and push. Adjust slowly until rim lays perfectly flat on glass. I've found starting with as true a rim as possible before lacing up results in much stronger wheel with more even tension and less likely to go out of true in the long run. Heck, I've seen brand new rims that needed some bending to lay flat.
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Old 05-18-12, 01:22 PM   #12
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I'm a snob: if I'm going to put the time into building a wheel, I'll almost always opt for a new rim. Unless the rim is something really, really special.
LOL! My labour during my free-time is cheap! I'm sort of the opposite. It takes my only about 30 minutes to assemble a wheel from parts and get to fairly good tension, so I find myself keeping old rims and hubs in stock that others might throw away. So far, I've given away quite a few wheels as replacements, enabling quite a few boys and their families to continue to ride their bikes which would otherwise sit there collecting dust as they could neither afford to replace that bike or have it professionally repaired.
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Old 05-19-12, 05:50 AM   #13
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Also a glass coffee table makes a great jig to measure flatness of rim. Lay it on the coffee table and notice the opposing high and low spots. Grab two opposing high-spots and place the low-spots on the edge of a door-jamb and push. Adjust slowly until rim lays perfectly flat on glass. I've found starting with as true a rim as possible before lacing up results in much stronger wheel with more even tension and less likely to go out of true in the long run. Heck, I've seen brand new rims that needed some bending to lay flat.
Same here. I use a window, though
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Old 06-23-12, 06:00 AM   #14
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Don't mean to hijack this thread (if it's still alive) but I have a related question. I know my "new" used rim is flat with no hi/lo spots, but I'm wondering if I should re-use the old spokes from my cracked rim? Any ideas? Thanks...
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Old 06-23-12, 07:20 AM   #15
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Quote:
Originally Posted by ThermionicScott View Post
Seems like somebody on BF had made a jig to hold a rim stationary and press/pull on high/low spots to bend them back into true... can't find it now, of course.
I made a plywood jig and straightened a flat spotted rim with c-clamps once, and it worked well. I don't think I posted about it.

However, within a few hundred miles the rim seam (very near the flat spot) started showing signs of coming apart.

Coincidence? Not sure.
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Old 06-23-12, 08:36 AM   #16
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I'm a snob: if I'm going to put the time into building a wheel, I'll almost always opt for a new rim. Unless the rim is something really, really special.
That's me too. Pre-built wheels are so cheap that the only reason that makes sense to me for building your own is to make a wheel that's as good as I am able. That means starting with good parts.
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Old 06-23-12, 09:08 AM   #17
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LOL! My labour during my free-time is cheap! I'm sort of the opposite. It takes my only about 30 minutes to assemble a wheel from parts and get to fairly good tension, so I find myself keeping old rims and hubs in stock that others might throw away. So far, I've given away quite a few wheels as replacements, enabling quite a few boys and their families to continue to ride their bikes which would otherwise sit there collecting dust as they could neither afford to replace that bike or have it professionally repaired.
Agreed 100 percent! I am always on the look out for cheap used rims that are still perfectly serviceable even if they are perfect at all. I really don't worry about tiny dings or even some small flat spots. I don't ride fast enough to notice a tiny flat spot on a wheel that a perfectionist might notice.
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Old 06-23-12, 10:55 AM   #18
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Originally Posted by HillRider View Post
+1 on Scott's suggestion. Unlace it and lay the rim on a flat surface. If it lays flat or can be made flat with out serious effort and there are no major dings or kinks, you can likely reuse it successfully.
...assuming the rim itself hasn't suffered from all-around general fatigue. On rare occasion that'll be why the rim will be left in an undertensioned state. Then again, there'd be tons of obvious sidewall wear to boot if brakes had been used in the past for 30,000-40,000 miles plus over many years plus....

=8-)
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Old 06-23-12, 10:58 AM   #19
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Originally Posted by wxflyer View Post
Don't mean to hijack this thread (if it's still alive) but I have a related question. I know my "new" used rim is flat with no hi/lo spots, but I'm wondering if I should re-use the old spokes from my cracked rim? Any ideas? Thanks...

Watch my Youtube video for spoke reuse guidelines..

http://www.youtube.com/watch?v=hjdKJgh3d9Y&feature=plcp

=8-)
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Disclaimer:

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2. I like anyone will comment in other areas.
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4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
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Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
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