Sorry, this is probably a really simple matter but I thought I'd ask. Today a friend and I were trying to fit a Shimano SLX Cassette 10 Speed HG62 onto an Ultegra 10speed hub and it just wouldn't fit. I lined the spines up correctly it just seemed too narrow. I'm I wrong to think those should go together or should I have just pushed harder or what? I had an MTB wheel laying around so I pulled the SRAM cassette off and the SLX cassette just slipped right on...

Shimano made a couple of 10-speed only road hubs including the Dura Ace 7800 and the first series of Dura Ace and Ultegra 10-speed prebuilt wheels. These freehub bodies had taller splines and would only accept 10-speed cassettes that had deeper groves to match. The 10-speed cassettes would also fit on older 8/9/10-speed freehub bodies.

Your SLX HG62 cassette is one of the new Dyna Sys 10-speed MTB groups and Shimano may have reverted to the older shallow groves used on pre-10-speed cassettes. If your Ultegra hub is one of the 10-speed only designs, that may explain why the HG62 won't fit.

hmmm this bike is a 2009. it did come with ultegra rims.

from: https://sheldonbrown.com/dura-ace.html


2003 7800
10 speed, Hollowtech II Two Piece crank/bottom bracket
The 7800 hubs had an aluminum body, with taller-than-normal splines. Only compatible with 10 speed cassettes

2008 7850
7850 Freehub with titanium body, goes back to standard cassette dimensions; larger-diameter spline system between cassette body and hub shell, accepts all Hyperglide cassettes: 7-. 8-. 9- & 10-speed.


Maybe my 2009 bike had 2007 components slipped on it?

Yeah, I'm pretty sure it's one of the 'ten speed only' wheelsets.

So since the last time I posted I tried to have the freehub body replaced on the wheelset. The mechanic I brought the part to said it won't fit. I find it ironic I have a 6600 ultegra hub that won't accept a 6600 ultegra freehub body...

Anyway, Sheldon brown writes that you can file them down to accept all cassettes. I'm not a real mechnical guy but I think I see what he is saying. It's fairly obvious what needs to be filed. Has anyone ever done this? How safe is it? Where could I get this done? I'm assuming you would need a grinder b/c the amount of metal that needs to go is a lot.

I wouldn't do it. The 10-speed only freehub bodies were aluminum and had taller splines to prevent "notching" and distortion from the cogs since these splines were softer than previous steel or Ti freehub bodies. Filing them down to accept the shallower grooves in 8, 9 or apparently some 10-speed cassettes will lead to significant damage in use.

I looked at Sheldon Brown's articles on the aluminum freehub bodied Dura Ace and Ultegra hubs and didn't find any reference to his recommending filing these splines down to fit other cassettes. Where did you see it? In fact he specifically recommends against using any aluminum freehub body with Shimano's standard pattern cassettes. The only spline filing recommendation I've ever found from him is to convert older Hyperglide (steel) freehub bodies to Hyperglide-C configuration so they would accept an 11T smallest cog.