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cdouble
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252 Posts
Discussion Starter · #1 ·
I have a FSA V-Drive MegaExo 180mm crankset on my single speed. The left arm keeps working loose when I'm really pounding (is on a single speed). I've tightened the crankarm bolts as tight as I dare, but after an hour or two it works loose again.

I am thinking maybe there is some grit in there preventing it from tightening down all the way, so I think the next step will be to pull the arm off and really clean up the splines on the arm and the spindle and reattach. Two questions:

1. I know that a solvent like WD40 would do a great job of dissolving the crud, but I don't want any of that getting into the bearing, also not sure the residue would be good. So I'm thinking a toothbrush and some dish soap. Thoughts?

2. When I bought the crankset back in 2008 it came with a small vial of some amber liquid. No instructions or label. I figured it was supposed to go on the splines to help hold everything together (kind of like locktite). It seemed to work, the crank was rock solid for a few years. Then I had to pull the arm off to replace the BB, and it hasn't been the same since. What was that stuff and where can I get more of it?

Thanks all,
Chris
 

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The joy of ski is Yours
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1,367 Posts
Just take all the bolts out and clean everything. Since the Bolt for the spindle pre-loads the Bottom Bracket, the original thread lock has been used up.

Use Lithium Grease, since you have aluminum on Chromoly Steel, on the inner spline of the Crankarm. Slip it onto the spindle, apply new Blue threadloc and set your BB tension. Snug down the pinch bolts.

After this, give the Spindle bolt another snugging and you should be back in business. Maybe thread lock the pinch bolts also, but be sure to just cleanup everything including the bolt head locating holes.
 

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3,782 Posts
Obviously the pinch bolts work loose. The spline interface may be worn from running loose.
Use a torque wrench on the pinch bolts and tighten them to the high side of the recommended torque, working alternatively across the bolts.
Then re-torque them as often - starting with a ride around the block -as possible until they no longer tighten.
I had a FSA crank that would loosen and was able to fix it this way.
 
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