As the title suggests really - came on a new bike, slightly disconcerted when it fell off during tubeless conversion (I hadn't read up on it!), seems to work perfectly fine but I'm wondering if there should be some sort of cap on it that is missing? Here it is:
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I'm not sure there is really any space once the chain is on so presumably this is what it's supposed to look like...!
Looks normal mate
Good, thanks! It is so weird to be able to just lift your cassette off with your bare hands.
It coming off is nothing to do with it being an XD cassette that is just your freehub body coming off with the cassette on.
But yes that is normal, as the cassette is threaded there is no lockring,
So are there other designs where the same thing happens ie the freehub body is attached to the cassette but the whole unit is removable tool-free?
Yes, so even if the cassette was off you could just pull the freehub off and replace it for a 10sp one for example.
If it pulls off you really need to remove the cassette to re-seat the freehub on some hubs. Hope for example has a seal that has to be 'popped' back into place.
Eh?? It's a DT 350 hub, I can't see any sign of any seal that needs seating.
There's no lock ring required on a SRAM XD driver and cassette. As for your DT hub, check page 18 for an exploded diagram...
http://www.dtswiss.com/Resources/Support/HUBS/DT-Swiss-Hubs-350-Technical-Manual