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Old 01-19-07, 09:26 PM   #1
VT to CA
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This Problem Has to be Magical...

...because it sure as hell doesn't conform to any laws of God, nature or science.

I have chainring wobble- every revolution, boths rings swing outward slightly. I've tried two different cranksets (one of which has a one-piece carbon crank and spider) so I think I can safely rule out a bent spider, which was my LBS mechanic's opinion.

I've tried both cranks on two seperate bottom brackets (I use ISIS)- same problem, so I don't think it's the bottom bracket.

Both bottom brackets thread in easily, I can tighten the drive-side flush to the frame by hand.

At this point I'm thinking it has to be either odd threading on the frame, or the bottom bracket tube was welded crooked. (It's an '06 Cannondale CAAD8)

Or maybe it's magical and elves did it- I'm stumped. Any thoughts?
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Old 01-19-07, 09:43 PM   #2
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Put a dial indicator on it and measure the run out, then let us know.
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Old 01-19-07, 10:20 PM   #3
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Originally Posted by VT to CA
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At this point I'm thinking it has to be either odd threading on the frame, or the bottom bracket tube was welded crooked. (It's an '06 Cannondale CAAD8)

Or maybe it's magical and elves did it- I'm stumped. Any thoughts?
I'd go for the elves, because I doubt it has anything to do with the bottom bracket shell being crooked. If that were the case, the chainrings might be canted slightly, but it would not make them wobble as they rotate.
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Old 01-19-07, 10:38 PM   #4
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It must be one of the rotating parts that is out of true, Either the axle, the spider, or the chainring.
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Old 01-20-07, 10:38 PM   #5
VT to CA
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FINAL SCORE

Murphy's Law - 1
Magical Elves - 0

Would you believe both spiders were out of wack?... leveling table confirmed it... what are the chances of two new cranksets warped out of the box? Insane. The first was an FSA Energy (alloy) and the second a no-name carbon... surprising for FSA, I'm a big fan of their stuff. The third one (FSA K-Force Light) works like a charm...
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Old 01-20-07, 10:43 PM   #6
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FINAL SCORE

Murphy's Law - 1
Magical Elves - 0


Glad you figured this one out!
Sounds like FSA needs to work on their quality control.
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