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getto crank solution options

nh dude

Monkey
May 30, 2003
571
16
Vt
Been riding a slightly used demo for a few weeks. This demo has xt cranks While pedaling (thankfully) the left arm fell off of the spline on the spindle.

The plastic lock nut backed off (some threads are shot on it) under power or the pinch bolts did and the arm eventually wore its self loose causing the plastic lock nut start loosing threads.

The spline of the spindle is in good shape.
The spline of the crank arms is ok. You can see where some of them have slipped but are still decent.

I think arm keeps backing off because the plastic lock nut won't tighten down completely. I know that I am slowly killing my cranks each time the arm works itself off because the plastic lock nut is not doing its job.Even thought it works in unison with the pinch bolts.
This is why I believe Saint cranks used metal lock nut is this true?

SOLUTIONS
Current solution: Went to hardware store. They did not stock a metal nut with proper threads and diameter. So I re installed left arm. Spent $1.68 and made a basic headlock for my cranks. slightly snugged it up and rode it.

RESULT
So far the arm had not worked its self loose because the "head lock" is working as the plastic locknut. I know that if i tighten down to much on the "headlock" it could **** up my bearings if the cranks don't bottom out on the spindle. This leads me to believes the splines are ok along with the pinch bolts and I could potentially...

Order a metal lock nut that won't strip because its not made of plastic.
So the arm actually gets locked all the way down without a ghetto solution.



Replace the arm and get a metal lock nut.
about 60.00 this would be sure as **** the arm is solid.

Get new cranks
60.00- 90.00. this is expensive. the xt are sick and light. i ran the lx version in 2007 with no problems but that piece of plastic was never roached.

Thanks
 

freakrock

Monkey
Aug 19, 2005
431
0
Santiago de Chile
If you think that the plastic locknut is there to keep your cranks in place i wouldn't be surprised if the cause of your problems was too little torque on the pinchbolts. Make sure to tighten them to shimano's specs.
 

JRogers

talks too much
Mar 19, 2002
3,785
1
Claremont, CA
Could be wrong but my understanding is that the locknut is plastic because it doesn't require much torque. In any case, the cranks should not require much pressure to get the cranks in the right spot. If there's no play, should be no problem. Why not just get another plastic one and call it a day? Never had an issue with the plastic one on my XTs and it seems to tighten properly without much torque.
 

nh dude

Monkey
May 30, 2003
571
16
Vt
I'm aware that the plastic piece is not the the tightening component.
The pinch bolts are super tight. I keep at it with the new lock nut