So what does this screw do then?

[BigonaBianchi]

the little black screw on the black metal ring thing that is part of the axel hub gubbins??

Would this possibly have loosened and cause a little play in the wheel?? Could this possible be whats causing the derailer issues I have had in th eother thread in this forum?

Im tempted to just take it apart and find out but just in case thats got nothing to do with it I thought Id ask wiser men than me

Cheers

 

[RecordAceFromNew]

I have a hub that has something like it (see pic below), and it works like the bolts on the stem setting the preload on aheadset bearings.

I don't see any problem for you to release the wheel and see whether that black ring is loose. I would expect that bolt makes sure it is not.

 

[accountantpete]

I'd say it is a locknut. The grubscrew may tighten up against the axle and so prevent overtightening.

 

[02GF74]

I woud say it acts as a lock nut for for bearing prelod - the ring it is fitted to probaly is threaded so it stops it loosening or tightening.