ISIS Spline Lengths

Quick question:

Can anyone tell me if the actual length of the ISIS splines is uniform, or if it can change?

I ask because I read that KH cranks are meant to be used with a 6mm spacer to get the correct spacing between the rotor and the caliper.

However, on my current unicycle, with a 6mm spacer on the disk side, I have to Loctite the bolt and keep it tight or the crank will become loose on it’s own. I don’t recall having this issue on other uni’s with Spirit cranks.

I’m using a Nimbus Superwide hub, and just looking at the splines, they do seem to be shorter in appearance but I haven’t actually compared two side-by-side.

On my next build I’m planning on using Spirits, but had considered going to 4mm spacers on both sides in order to make sure I have full engagement of the splines, but if I use a different hub, perhaps I’ll still have full engagement with a 6mm spacer?

This stuff used to make so much more sense… :roll_eyes:


I don’t know for standard hubs but somewhere along the line Schlumpfs got slightly longer axles on the ISIS versions.

I would imagine that the spline length before the crank-stop would be part of the ISIS standard, but then we don’t have proper crank-stops :o.

I can measure a few hubs tomorrow if you want. (Nimubs regular and superwide)

If the step from 6 to 4 mm is too big for you: I used some 0.2mm shims in addition to my spacer to make it fit perfect.
See here (poor translation via google)

Eric P, I’d appreciate that as it’d be great to know for sure.

Yes, all the dimensions are in the spec. Doesn’t guarantee that everything’s built to spec of course.

I haven’t played with ISIS except on unicycles but all the drawings show a positive stop on the spindle for the arms to bottom out against, and the text says they should contact the stop before full torque is reached. Spacers must be a unicycle innovation. But I’d guess that snugging up tight against your spacers matters more than getting that last mm or so of spline engagement, based on the kinds of failure and damage that are actually likely to happen.

If you need ISIS spacers in 1mm increments, you can find them very cheap at your local Ducati dealership.

You want to ask for a Ducati 22mm drain plug crush washer. Stock number 22032083A.
They call them crush washers, but they’re actually just 1mm thick aluminum washers with a 22mm inside diameter. They worked really well for what I needed and were about $2 for a bag of 10 of them. You can hone in the ISIS spacing with them without having to grind down a bigger washer.

My measuring tape wasn’t where I thought i left it so I didn’t get any measurements but putting the two hubs against each other the new superwide hub with aluminum spindle was about 1mm shorter from bearing surface to end of the spindle. The other hub is an older standard 36h 100mm Nimbus ISIS hub.

The splines themselves also look quite different close to the hub, though the ends look the same.


Cool, so maybe I’m not going insane.

Thanks for the pic Eric!

Eddie, thanks for the link. Very interesting/useful information.