Bent BB spindle?

beagle

Senior Retro Guru
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.
 
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.
 
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.
 
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.
 
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.
 
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.
 
Back
Top