I got that problem on KH Spirit cranks on a KH Spirit hub. The bolt bottoms out on the spindle.
I’m using a 4mm spacer right now. Using a shorter or no spacer leads to play normal to the axis. Greasing the spindle helped temporarily, but only for a couple of hours.
The crank seems to have some rotational play on the hub. The creaking occurs reliably when I first push the pedal/crank in one direction and then the other direction, e.g. first forward/accelerate the wheel, then backwards/decelerate.
A dealer recommended to just buy a new set of cranks and consider ISIS cranks expendable items. Q: Any better ideas or hacks?
A rider recommended me to just live with the creaking noise and rotational play and suggested it won’t get worse. Q: Can anyone confirm or disprove that?
While I hate that idea probably as much as you do, it seems to be the normal practice. As far as I can tell, right KH spirits are especially prone to issues, as they get extra torque from the brake, and can’t be spaced inwards much, as they run into disk-frame issues.
Since you tried grease already, loctite 641 on the splines would be my only idea that I can think of. It’s designed to hold bearings onto shafts, that may need disassembly for maintenance. Sounds like it may work to me, and I know people had at least some succes with regular (bolt securing) loctite.
I haven’t seen or heard of anyone damaging their hub from this problem (and I know quite a few people using the “ignore it”-method), so while the creaking and movement may get worse, I don’t think you will cause further issues.
I intended to reinstall the cranks using some Loctite 641. I discovered that my 4mm spacers weren’t 4mm but 4.5mm and 3.7mm, the former having been on the creaking side, I think. So I measured and concluded that actual 4mm ones would fit good and applied such instead. I also applied some of that green Loctite. Wait, green? It seems to be supposed to be yellow. It’s a Chinese bottle, can’t tell whether its fake, legit but wrongly labelled, or just legit.
Anyway, there’s no creaking any more but also no grounds to draw any new conclusions from this.