Cassette locking problem

[thistle]

Today while speeding down a hill (on road) I 'lost power'. I assumed the chain had come off or snapped so pulled in and had a look but the chain had dropped between the 11 and 13 tooth cogs because the lockring had come undone.

This shouldn't happen should it? The lockring was put on tight on Saturday so it's not had long to work loose.

The cassette is a Shimano 7 speed HG50 11-34 and the hub is a Shimano M756 with a spacer.

Are there any known bad hub/cassette combinations? Searching on google isn't much help as it just gives you shops that sell the parts.

I'm tempted to go to 8/9 speed but that would also mean a new controller (and brake lever).

[martinw]

I had that same problem on my old hardtail, the lockring came loose a few times, have you got the right tools to tighten it properly?

I ended up putting a dab of loctite threadlock on mine and it stayed put after that.

[Oggy]

You may want to check the thread on it to to see if its crossed or damaged in any way, bit strange thats its come loose on its own. As martin said a drop of threadlock to

[thistle]

Yeah I've got the tool that slots in.
The threads on the lock ring look OK and the threads inside the hub also look OK.
I've tightened it up as much as I reasonably can with a 9" spanner so I'll see if it's any better tomorrow. At least now I know if it's shifting even worse than normal then it's the cassette.

I think there's definitely far too much play in the whole thing which probably doesn't help. Might require a trip to the bike hospital.