I bought a little hardcore frame. Due to drastically limited stock where I am, I ended up with a choice between two models from a supplier, 135 and 142mm. Since neither are boost, I had two 135mm hubs already so built a new wheel and decided to slap a 12spd HG cassette on, use a Deore 12sp shifter and rear mech, and a goat link.
The cassette I bought has 10 sprockets on the main body. 11 and 12 are loose. When I slot the cassette onto my existing hubs I have a wobble problem. Sprocket 12 sits on top, so it's the main body, and particularly sprocket 11 that wobbles. One hub that sprocket rattles, one it just moves a bit.
It's like a Spacer is needed behind the cassette, or the manufactured thickness of the cassette is wrong? I've sent off for a pack of spacers (1mm, 1.5mm, 2mm) so nfe they're cheap to try. But aleverythong I read online talks about the opposite problem, using spacers with smaller number of sprocket cassettes, not larger sprocket ones.
Am I doing something wrong? Or the cassette is not manufactured properly?
Update: I did find some information about HG and HG-C (Hyperglide Compact) freehub on Sheldon's website.
Whilst my freehub looks like a HG-C, it was the longer length of a HG freehub. It's an obscure brand from Taiwan that came on a full bike build (land of the 30.4mm seatpost!)
A 1mm Spacer behind the cassette sorted my issue, which was the recommended action for this trying to fit modern many-sprocket cassettes on an older HG freehub. I don't think this is likely to happen to many people, but that's the solution if you fit a HG 11/12/13 speed cassette and it seems too thin for the freehub and wobbles.
I had this recently, one was a Shimano 11 speed cassette on a Stan's hub, the other a 11-46 Shimano 10 speed on a Hunt gravel wheelset so you're not alone. Took a while to find the source of the rattle because when I initially fitted the cassette it seemed fine.
Happybiker are sure yours don't just have 11 speed road freehubs (same solution different issue).