loose cassette lockring (6700)

DiscoBoy Posts: 905
edited April 2014 in Workshop
My mum's bike had a mystery noise. We tried the usual suspects like bottle cages, spokes etc. to see if they were the cause, to no avail. I grabbed the cassette, and discovered that the smaller sprockets could move a little, independently of the large ones.

I came to take off the cassette, and I didn't need my lockring tool: I could have taken it off by hand, it was that loose. The inner teeth of the cassette look fine, the hub (DT Swiss) splines aren't perfect, but aren't too chewed up. I re-fitted the cassette and tightened the lockring up tight, and now it seems fine...

The bike was in a crash not long ago, and took a rear-end NDS bang on the quick-release, so that might be related. The bike/cassette isn't that old, it is on its first chain which is nearly at the first wear thingy on a chain checker, but not quite so a few thousand miles in (it is well looked after in the clean & lube department).

So... What could have caused this? Is something broken that I don't know about? Was it not tight enough to begin with? (the bike was built by the shop) Might the crash have caused it to slip? Will it be okay now?

Obviously I'm going to keep an eye on it to see what happens next...
Red bikes are the fastest.


  • Probably not been correctly fitted in the first place. If the lockring and freehub isnt damaged, and it is tightened to the correct torque it should not undo again.
  • buckmulligan
    buckmulligan Posts: 1,031
    I can't imagine how a crash (rear-end or otherwise) might have caused a cassette lock ring to come undone.

    I'd agree with the above, if it seems nice and secure now I'd say it probably hadn't been torqued up correctly to start with. It sounds as though you've given it a good check over, so keep an eye on it and have a check of the little rings again every now and then.
  • DiscoBoy
    DiscoBoy Posts: 905
    Okay, thanks guys. So it looks like it was down to the original torquing. Like I said, I'll keep an eye on it and see if it loosens again.

    I've always said that the major downside to BMCs is that you can only buy them in one chain of bike shops... Whom I never really rated, and certainly don't now!
    Red bikes are the fastest.