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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 05-22-06, 09:08 PM   #1
superkevin561
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"Tacoed" wheel on new (used) road bike

Hi,

I'm new to road biking and just this weekend I rode my 2000 Cannondale R2000 --- purchased on ebay --- for the first time. Unfortunately the ride didn't go so well.

At some point, I heard a metallic popping sound and my rear wheel started skipping back and forth. I nearly lost control of the bike, but was able to slow to a stop without injury. The wheel is completely destroyed: the rim is warped, the tube is punctured, I'm not sure if the spokes can be salvaged, and the tire might also have to go. See the results here and here.

The most disconcerting part of all of this is that I don't know exactly how this happened. There was a pothole on the road but I don't think I hit it. Is there anything that could cause something like this to happen spontaneously? I did not check the spoke tensions before riding, which now I realize was a mistake. I weigh ~190 pounds; could my weight on a wheel with a few loose spokes cause something like this?

Thanks,
Kevin
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Old 05-22-06, 09:23 PM   #2
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I weigh ~190 pounds; could my weight on a wheel with a few loose spokes cause something like this?
Yes.

Are you sure the rim is really bent or is the wheel just out of true? If so you can probably just respoke the wheel and retrue.
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Old 05-22-06, 09:38 PM   #3
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Are you sure the rim is really bent or is the wheel just out of true?
Did you look at the pictures he posted? The wheel is bent about three inches. That's way past "out of true".

That wheel is likely history. I doubt that a shop would attempt to rebuild that rim into a wheel. Although it's possible that the spokes were undertensioned, I think it's much more likely that they were way over tensioned. In Jobst Brandt's book he describes how to find the maximum tension that a rim can take. Basically, he says to keep tightening the spokes until the rim starts to collapse (= taco), and then back off a little. If a rim is right at the limit of maximum tension and it gets some shock (like a heavy rider hitting a good bump) then what happenned to the OP is exactly what I'd expect to happen - the wheel would collapse.

If possible, I'd contact the Ebay seller and ask about the history of that wheel. You may find that it was reworked by someone who was not careful about exceeding maximum tension for that rim. BTW, it would be interesting to hear what the rim was (manufacturer and model#).
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Old 05-22-06, 09:49 PM   #4
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Thanks for your replies. The rim is (was) a Mavic Open Pro.
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Old 05-22-06, 09:50 PM   #5
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In my experience, a wheel generally fails around the spoke nipple when over tensioned. This shows us as radial cracks around the nipple which itself is rising above the plane of the rim - like a miniature volcano rising from a plane. Also, there sometimes are tearing cracks between the inside of the rim and the sidewall. Look for these. If they don't exist, it may be uneven spoke tension.

Don't every try to reuse spokes - its not worth it.

Look closely at the flanges of the hub - have the current spokes elongated the spoke holes? Have they left deep depressions in the sides of the flange? If so, the hub may not be worth saving.

Right now, its possible to find a decent new 9speed wheel with shimano hub for a bargain and retailers (including chains and internet) are unloading their old stock. So, for $100 or so you can start fresh.
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Old 05-22-06, 10:02 PM   #6
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sidewall cracks

Cactus -- thanks for your advice. I inspected the inside sidewalls and found some more evidence -- are these the types of cracks you're talking about: crack 1, crack 2?

Thanks again.
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Old 05-22-06, 10:07 PM   #7
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Originally Posted by superkevin561
Cactus -- thanks for your advice. I inspected the inside sidewalls and found some more evidence -- are these the types of cracks you're talking about: crack 1, crack 2?

Thanks again.
Geez! No, those aren't quite the cracks he was talking about - it looks like you tore the rim apart! Are those cracks 180 degrees from each other, and how sure are you that you didn't hit that pothole?
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Old 05-22-06, 10:08 PM   #8
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Originally Posted by superkevin561
Cactus -- thanks for your advice. I inspected the inside sidewalls and found some more evidence -- are these the types of cracks you're talking about: crack 1, crack 2?

Thanks again.
What those picture tell me are a few things:

1. That rim is far beyond salvage. Forget it.
2. I am more convinced now that the rim was way overtensioned.
3. Nice Gatorskins. Still lots of miles left in that tire ;-)
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Old 05-22-06, 10:12 PM   #9
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The main reason I don't think I hit the pothole is because I never felt a bump. I also think that the wheel broke somewhere past the pothole, but I can't be confident about this because at the time all that I was focused on was trying not to crash.
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Old 05-22-06, 10:14 PM   #10
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Oh, also, the cracks were not 180 degrees apart -- more like 60 degrees.
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Old 05-23-06, 12:00 AM   #11
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If the wheel was straight when the bike was delivered, then the spokes weren't overtensioned. One of the wheel-building philsophies is to tighten up the spokes so much that the wheel tacos, then loosen up the spokes so that it's straight again. If it wasn't tacoed on the truing stand from spoke-tension, it wasn't overtensioned.

However, the failure here looks like the seam where the horizontal and vertical parts of the rim are joined. Appears there's a dent or wrinkle in the 2nd photo. My guess is that this wheel was previously damaged, then it was straighten out just barely with truing, which required all sorts of uneven spoke-tension in order to keep the rim straight. THen with additional loads from this first ride, the uneven forces just ripped the wheel apart.

Last edited by DannoXYZ; 05-23-06 at 05:29 AM.
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Old 05-23-06, 12:42 AM   #12
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Did you look at the pictures he posted?
There were no pictures when I posted. What the ****? Is that a radially laced rear wheel? Sorry it's 2.30 am here and my eyes seem to be deceiving me. Whoever built your wheel is an idiot, that was just asking for it.

And to echo the above, you can salvage that rim for scrap aluminum.
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Old 05-23-06, 12:43 AM   #13
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Originally Posted by superkevin561
Thanks for your replies. The rim is (was) a Mavic Open Pro.
The rim may be recoverable if you go to a conventional 3x lacing pattern. The wheels look to me to have radial on the non-drive side and 2 or 3x on the drive side. What are the spokes? Look like they may be revolution...poor choice of spokes and lacing pattern for a larger rider. Botique wheels for anyone who is more than 150lbs is a waste and dangerous unless the design is carefully looked at. I am 225# and I use Open Pro rims to build my wheels with 32H 14/15 spokes and a 3X lacing. I use 36H on my cross wheels. I have a set that I built up 2 years ago for the road and I haven't had to touch them with a spoke wrench. I have more than 8K on those wheels. I will be truing the rear wheel before the BTC in western Colorado this year.
I have had a wheel that I over tightened and broke a spoke when I was stress relieving the wheel, that looked like yours but, I just loosened up the spokes replaced the broken one and retrued the wheel. The wheel is 5 years old and still going. Find a good wheel builder in your area and have him look. I am sure that he will recommend going to a traditional wheel lacing pattern at your size and will probably use the same hubs and rim. Good luck.
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Old 05-23-06, 12:51 AM   #14
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Ouch!!!! I didn't see the cracks. How old was the wheel? I have some serious miles on a 15 year old set of Open Pro wheels and they are perfect. Stay away from radially spoking patterns because of the tension required to keep them straight. Most radial spoked wheels are designed and engineered for the job. If you are a light weight (120#) you can get away with radial spoking conventional rims like Open Pros otherwise go conventional.
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Old 05-23-06, 05:22 AM   #15
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Originally Posted by DannoXYZ
My guess is that this wheel was previously damaged, then it was straighten out barely straight with truing, which required all sorts of uneven spoke-tension in order to keep the rim straight. THen with additional loads from this first ride, the uneven forces just ripped the wheel apart.
+1. Add to that "unconventional" lacing, and an old rim. (CAAD 4s are pre-1999 era, I think. The wheel is probably original equipment).

You can pick up a pair of OP wheels hand-built by Excel Sports (http://www.excelsports.com/new.asp?p...jor=1&minor=24) for a fair price. I'd recommend a 32 spoke count, with conventional 3x lacing. These should hold up just fine for you, and last a long time.

(BTW, I'm suggesting a pair of wheels, because I don't know where you'd ever find a gold OP rim to match your front wheel, or a gold hub for that matter.....except maybe on e-bay, and that's how you got into this mess in the first place).

Bob
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Old 05-23-06, 06:42 AM   #16
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Yes, the pix you provided could be a sign of overtensioning.

I agree with dannoxyz except that over tensioning is likely. In the process of trying to straighten out a rim, not only is uneven tension required, most often some spokes require very high tension (to overcome the anomolies ing the rim). Its a little like a rear wheel where spokes on one side have very high tension. Only, in this case the high tension spokes are not located uniformily around one side. Rather, they are located either in a section pulling to both hub flanges when the problem is a high spot, or they are located on one side for a way then the other side for a way when the problem is a lateral wobble. In either case, the wheel overall may not be overtensioned, but the specific overtensioned spokes will destroy the rim.

At your weight (close to mine), you're probably better off with a 36 spoke rear wheel. If you build or buy a custom wheel, it should have double butted spokes. While Open Pros are nice rims, you might be better off with a CXP-33 - the "aero" shape make a stronger rim. But, again, if you find a nice wheel for $100-140, don't worry about either of these factors - take it and ride.
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Old 05-23-06, 07:40 AM   #17
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Originally Posted by Bobby Lex
+1. Add to that "unconventional" lacing, and an old rim. (CAAD 4s are pre-1999 era, I think. The wheel is probably original equipment).

You can pick up a pair of OP wheels hand-built by Excel Sports (http://www.excelsports.com/new.asp?p...jor=1&minor=24) for a fair price. I'd recommend a 32 spoke count, with conventional 3x lacing. These should hold up just fine for you, and last a long time.

(BTW, I'm suggesting a pair of wheels, because I don't know where you'd ever find a gold OP rim to match your front wheel, or a gold hub for that matter.....except maybe on e-bay, and that's how you got into this mess in the first place).

Bob
This is the best deal I've seen on OP prebuilts: (dura-ace ($320) or ultegra ($225) ) -- both screamers of a deal
http://www.performancebike.com/shop/...tegory_id=5320

I'd buy these, then take them to an LBS and have them check tension and even the tension out. Make sure they get stress relieved. Do all this before riding them if possible. You'll need an experienced wheelbuilder to get this done right. Then these wheels will last another 5-10 years.

Also, all Shimano hubs come over-tightened from the factory. Have the shop loosen them up so that with the QR just barely secured, the wheel will wobble on the bearings (so you can feel and hear the knock when wiggled side-to-side at the rim). Then, when you close the QR, and the wobble goes away -- perfectly adjusted.
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Old 05-23-06, 08:25 AM   #18
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I'm guessing from the craptacular rim strips (see the crack pictures, it's got the plastic junk) that this was a machine-built wheel in the first place. It might have been "repaired" in the form of a massive re-true to correct some damage from a big hit, which resulted in uneven tension as someone else suggested. However, you'd thing for something like that someone would have had to replace a spoke or two, and probably would have junked that rim tape. Check it for bends and wrinkles around the spoke holes where someone might have peeled it up, that would be a sign of old repair. I'd also check for radial cracks around where the spokes go through the rim; somebody said this early on but then we saw the other cracks. The eylets may have prevented them to some degree, but it's worth checking out.

One thing the OP should know is that a 190 lb rider on a 28h wheel laced 2x (or 3x) drive, radial non-drive is not at all out of line -- I'm biggern' you (205) and I run a 24h rear on my road bike, which is pushing it, but I'm nice to the thing. Radial non-drive wheels scare the old-schoolers, but on a highly dished rear they can be very strong, and they avoid the problem of breaking leading L side spokes from detensioning as you stomp down hard, which on low spoke count wheels is especially bad.

I'd get in touch with your ebay seller and tell him he sold you an exploding wheel. If they're cool about it you might get the cost of your wheel build out of him. Let us know where in the country you are and we might be able to reccomend a builder as well; if your hub is in good shape it might be cheaper or the same to rebuild than get new stuff, and a hand-built wheel is a better investment anyway.

This is a good lesson to all of us to remember to check the tension on used wheels no matter how antsy we are to try out our new toys.
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Old 05-23-06, 09:27 AM   #19
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Sorry, but When I open the pictures of the warped-ness I just had to laugh.

You say you bought it off ebay? You really should have checked the tension. But I know to check every little thing would take hours...
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