Shimano Crank Arm movement/loose

Served a few years now but I’ve noticed a wee bit of play in the non drive side crank arm, preload bolt is as tight as it needs to be and pinch bolts are done up well too. Guessing the splines might be worn, reckon they may just be on the way to a failure or is there anything else worth checking/tightening?

Take it apart & have a look, clean it up to see if anything looks damaged. They’re easy to take apart.

It’s been taken apart, cleaned and inspected but I can’t see any damage to the crank arm splines or the axle splines either.

I’ve never experienced it so other will hopefully have better suggestions.
Bolts threaded the crank maybe, or something stuck between the gap where the plastic doofer goes?
Got another left crank to swap in to test it? A road one might even fit. If the axle is steel & the problem is the left crank, then you could just buy a new left crank.

Sure it is the crank arm moving relative to the axle, and not the left bearing that is shot?

Bottom Bracket is pretty new only done a few rides on it. Plastic spacer/pin thing is ok I think, I’ve had them perish before and that’s caused issues but this one looks ok. Going to take it all apart again and check it all.

Splines on the crank arm will be worn.

You may be able to save it by cleaning it all up and tightening the clamp bolts to the top of the acceptable torque setting* – it’s a lot tighter than you think if doing it by hand. The bolts need doing up alternately until they are *both* at the right torque.

If they aren’t done up tightly enough in the first place, the crank arm moves slightly and becomes looser as it wears.

The preload bolt is just that – it’s to ensure that the slack is taken out of the setup before the crank arm clamp is tightened. It doesn’t perform any function in terms of keeping the arm on.

(*Probably 12 – 14 Nm, but check the Shimano manual for your cranks.)

Check for cracking at the spider or along the crank arm. Apparently there’s some duff road stuff doing the rounds where grants have sheared off while in use.

I’ll run them on the spare bike until they fall off then replace them. I should have bookmarked the link for the cheap SLX cranks someone shared a few weeks back now.

https://www.sjscycles.co.uk/cranks/170-shimano-slx-fcm665-left-hand-crank-arm/

edit: that’s just a left one though.