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· "Cypress Gardens" Fl.
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These are pics of my 'Mavic' "Open 4 CD" rim that was destined to fail. If I had'nt of caught it, it most certainly would've. These were the original rims on my bike, and have about 10,000 miles on them,...so I cant complain. They've held up straight and true the whole time, having to carry my 240 lb a$$ over chip seal, pot holes, ruts, curbs, you name it. I've only had to put a spoke wrench to it maybe twice, and that was IT. They've been great rims. My new rims are 'Ambrosio' "Excellence" (the hard to find red ones)

As you can see in the first pic it was already starting to come apart at the crack near the eyelet. The second pic is another crack about 5 eyelets from the first, and not as well defined but definitely there. What do you guys think,......"Immenent Failure???"
 

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Imminent failure?

croswell1 said:
As you can see in the first pic it was already starting to come apart at the crack near the eyelet. The second pic is another crack about 5 eyelets from the first, and not as well defined but definitely there. What do you guys think,......"Immenent Failure???"
What do you mean by "Imminent Failure"? This rim has already failed - it cracked around the eyelete, detensioning the spoke.

Do you mean something more in the lines of "catastrophic failure"? Then I doubt it. When a rim cracks around the spoke hole, the spoke tends to gradually pull out of the rim. In the case of a spoke failure, the spoke tends to hold tension and then suddenly let go. When a rim cracks at the spoke hole, the end result is the same as if the spoke broke, except that it tends to go at a much more gradual rate.

Rim cracks around the spoke holes are unlikely to propogate through the rim (i.e they don't result in complete rim breakage). These cracks are formed through fatigue, and fatigue only occurs in tension. The rim is in tension immediately adjacet to the spoke holes, but the combined affect of all the spokes pulling inward put the rest of the rim in net compression, so cracks propogating completely through a rim is extremely rare.
 

· Big is relative
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I agree with Mark. As soon as the rim cracked, the stress was gone. It probably transferred to another part of the rim, but the overall stress was lower. I am an engineer geek. I used to race on those rims and cracked two rear ones but I alway got good life out of them before they broke. The cracks never propagated any further, just felt like a broken spoke.
 

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"Normal" rim failure.
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Rear, and sometimes front rims will do this, given enough time and/or miles. The wheel will go "out of true" when this happens. You may try to tighten up the spokes, but after a few miles, the rim will just crack more. I've never seen a crash because of something like this. When the wheel is rebuilt, you can use the same spokes. Just don't remove them from the hub.
 

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This is a design failure of the rim. Cracking around the eyelets is what happens when you use hard anodizing as a surface treatment. Despite knowing about this problem, Mavic continues to market this as a premium feature. It's shameful.
 
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