Crankset doesn't rotate in a straight line

[TonyN98]

Every time I pedal the crankset moves in and out. This means that I can't adjust my front derailleur properly as the chain moves from side to side, hitting the derailleur at every rotation. There is no play in the bottom bracket, the crankset has been secured well to the BB by the crank bolts and the crankset is not bent in any way. What could be the cause of this problem? Thanks.

 

[raleighnut]

It's not sitting square on the shaft, I'd remove and refit it.

 

[Profpointy]

Mine did that. Turned out the axle was bent - which rather suprised me as it was a 1/2" solid steel bar. Replaced BB and crankset in the wnd, but just the BB would have done I guess. This was a traditional square taper type.

 

[fossyant]

Wonky chain rings, bent axel, or just crap quality/cheap

 

[User6179]

Bent BB axel maybe ,

My Spesh sirrus chainring started hitting the mech cycling home one day about half a mile from my LBS so I called in as he had just fitted a new crank and BB the day before, turned out the frame had cracked along the weld at the bottom bracket .

 

[TonyN98]

Thanks for your replies people. Here is a video link of what happens so you can visualize it.
View: https://www.youtube.com/watch?v=3zcWbsVlzTQ&feature=youtu.be
I will take it to my LBS if the problem persists.

 

[TonyN98]

Problem solved, thanks.

 

[mjr]

Are you sure that's not a problem with the wheel or just the small ring? I think it's hard to tell with the camera viewpoint wobbling around, though.

 

[Stephen Piper]

Looks like the chain itself is bent

 

[goody]

Chain looks fine but it's the bike that looks wobbly.

 

[Levo-Lon]

After watching that vid i need to pop and see the Purser

 

[Psycolist]

Land Ahoy m'hearties
It did look like a chain problem didn't it, like it had been kinked or bent in one area.

 

[keithmac]

I had to check the front pulley axial runout on the Gteck (carbon belt).

Turn bike upside down and use a cable tied taped to bottom fame tube to gauge the axial runout on the sprockets, site it 0.5mm away from inside face/ teeth and spin the crank to check..

 

[Ajax Bay]

the axial runout on the sprockets

What is this?

 

[keithmac]

Axial is in/out radial is up/down.

A perfect crank will have zero runout/ deviation on both.