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Ok so I have a GXP BB and Firex cranks. All was fine the first time I fit it. However, ever since taking it off and refitting with new BB the non-drive crank arm keeps coming loose - I even threadlocked it to death.
So today I started changing from an SS to a 1x9. The BB shell is 68mm, so acording to the instructions that would be 1 spacer each side, which is what I had on the SS setup. However, I now have a chainguide so I put that in on the drive side and one spacer on the non-drive.
However, two things:
1) I have a massive gap between the crank and BB which I must have had before (but didnt notive) when the crank arm was falling off and this is not possible to reduce as the BB cup on the non-drive has a lip on it which stops it going so far.
2) The chainline is totally off centre and if I shim it up any more aren't I going to reduce the already (it seems) inadequate ammount of spindle coming out the other side?
I even tried double spacer on non drive and just chainguide on the drive but that only reduced the gap the spacer width (obviously) and the chain line is still off.
Ideas?
Cheers
[i]1) I have a massive gap between the crank and BB which I must have had before (but didnt notive) when the crank arm was falling off and this is not possible to reduce as the BB cup on the non-drive has a lip on it which stops it going so far.[/i]
Normal
[i]2) The chainline is totally off centre and if I shim it up any more aren't I going to reduce the already (it seems) inadequate ammount of spindle coming out the other side?[/i]
Yep
Solution: change to different chainset. I've got a Fire-X GXP chainset and got bored with it constantly coming loose and it's currently languishing deep in the shed somewhere. I'd sell it if I didn't feel guilty at the suffering and frustration I would cause the buyer.
nuke - if i could afford to i would. one day i will change but until i magic some money up i need to find a workable solution.
I solved my fire-x coming loose by using about double the recommend torque it's been fine since.
hmm ok maybe its just a spacing issue then - i thought i should try and keep the overall bb length to 73mm but reading some other forums other people seem to space out the drive with another spacer ie. 3 spacers in total + the chain guide.
though any other thoughts let me know - will have another go tommorow night
Unfortunately as you have already worked out, and as shown here
at 1:10 onwards.
There is not much you can do with GXP crank arms if there is any play in the fit on to the BB axle.