This is driving me daft. I got a set of Khamsin wheels on special offer from Halfords a few weeks ago. Fitted my near-new Ultegra 10-sp cassette to the wheels last night, and the freehub seems to be too small (radially) for the cassette. There’s about a ~0.5-1mm gap which allows the cassette to move radially – enough for the wheel to make a clink-ching every time it goes over a bump. I’ve fitted the 11-sp to 10sp spacer that came with the wheels. I’ve checked and re-checked and triple checked I’ve used all the correct cogs and spacers for the cassette. I’ve checked the lockring is tightened to 40Nm….and still it’s loose!

Please someone solve this mystery!

Because you’ve put a shimano cassette on a campag freehub?

Ah, I should have mentioned – I also double checked that I ordered the Shimano freehub version of the wheels. The box certainly says HG on it, which I presume means HyperGlide. Never actually seen a campag freehub though, so can’t say for sure if I have the wrong wheels in the right box

I think you need a little shim ( the size of which I can’t remember) the free hub will take either 11sp or 10sp but needs the shim with 10sp

Just checked the image at 700 and it’s definitely the HG version I have.

The 2 fittings are incompatible so you’ve got the right free hub. You’ll need a spacer though.

You need both the 1.85mm 11spd/10spd spacer, as well as the 1.0mm one that should have been on your 10 spd Ultegra cassette when it was on the 10spd free hub body.

The cassette body has the same physical dimensions as the Shimano unit, so you need the same spacer set.

The cassette body / wheel comes with the 1.85 mm spacer that you would use if you were fitting a 9s cassette. The 1.85 mm spacer reduces the effective width of the cassette body to that of the original Shimano 8/9/10s width bodies.

The 10s cassette itself comes, as others have noted, with a 1 mm spacer to fit behind the biggest sprocket, so for a 10s fitting, you will need that, plus the 1.85 mm spacer .

An 11s cassette needs no spacers behind it.

Thanks all – in all this time I’d never noticed (or maybe I’ve just forgotten!) that there was a spacer behind 10s shimano cassettes. I couldn’t find the original spacer, but I found a 2mm one in the garage and it seems to have done the trick. Thanks again – may good karma come your way! Kudos too to RJ Chicken & Sons who also mailed me with a proper detailed explanation.