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 Post subject: Bent BB spindle?
PostPosted: Fri Dec 17, 2010 4:08 pm 
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Joined: Thu Aug 06, 2009 5:48 pm
Posts: 868
I recently bought a frame and some other bits. The frame has a KCNC crankset fitted to it, not a brand I'm familiar with but they seem to be fairly expensive cranks. First thing I noticed was loads of play in the bottom bracket, so I took it to a the LBS to get it sorted as I don't have the right tools. First report back was that the bearings were knackered, fair enough. But now I'm told there's still play after replacing the bearings, and it's because the spindle is bent due to the previous owner riding with the play in the BB. Does this happen? You'd think (hope) it would take a lot more than riding on iffy bearings to bend the spindle. I could see it the other way round, but wouldn't it take a hell of a whack to bend the BB spindle? I can't see that the leverage is there but obviously I'm no engineer. Also, the spindle is bent because of the bearings but the cups are OK?

I have no reason to think they're lying to me and I don't think they are. Something doesn't seem to add up though, just wondered if anyone had any thoughts on it.


Last edited by beagle on Fri Dec 17, 2010 4:22 pm, edited 1 time in total.

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 Post subject:
PostPosted: Fri Dec 17, 2010 4:19 pm 
Old School Grand Master

Joined: Sun Jun 27, 2010 9:37 am
Posts: 3976
would be very surprised if the spindle is bent. more likely the cups are worn, or the pedals are knackered. what does it feel like? when you wiggle one crank arm does the other move too? if you measure the distance between the pedals at the top and bottom of the strok, and they are different then its the spindle, or the crank tapers.


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 Post subject: Re: Bent BB spindle?
PostPosted: Fri Dec 17, 2010 4:22 pm 
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I think other crank does move when you wiggle one side, there was tons of play in it last time I saw it (they've had it a week now). It felt as if the spindle was too long, but there was also front/back and up/down movement. It seemed to me that the drive side bearing was causing the problem.


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PostPosted: Fri Dec 17, 2010 6:51 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
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Location: New Forest, UK
Is it one of those ones with outboard bearings? It's certainly possible to enlarge and ovalise the cups on them and end up with a wobbly bottom bracket.


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PostPosted: Fri Dec 17, 2010 7:16 pm 
Gold Trader
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Joined: Wed Jun 20, 2007 11:19 pm
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Location: Odense, Denmark
KCNC has an alloy axle. Difficult to bend but maybe not so difficult to wear a groove into, which would give similar results.

We fitted one of these where I worked until recently and I wasn't enamoured.

KCNC is generally one of my pet hates though.


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 Post subject:
PostPosted: Sat Dec 18, 2010 1:54 pm 
Dirt Disciple

Joined: Thu Dec 16, 2010 5:58 pm
Posts: 26
take it its not a sealed bottom bracket, then the width of the bottom bracket axle flanges might be something to do with it, sounds like they could be too narrow.


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