I hope someone can help me with this problem. A wheel change necessitated a new cassette because my old one refused to come off (cassette lock sheared off! - it was old). The old cassette was 6 gears and the new one is 8 gears Shimano.
Since only 6 gears were being indexed I put new shifters and a rear derailleur on my christmas list. I put them on yesterday but have run into a problem with the rear derailleur (Shimano Sora RD-3300 8 speed).
The pulley is rubbing against the cog. I've adjusted the b-screw from one extreme to the other but it has made no difference whatsoever. It is positioned correctly (against that bit on the frame - sorry I don't know the technical word for it). I've tried shifting up and down as well as observing as I adjust and there's absolutely no difference.
Temporarily I've 'solved' the problem by pulling the cable housing that goes into the derailleur up over a bolt that holds the mud guards in place. This has the effect of moving the derailleur so that the pulley positions a bit further away and no longer rubs. However, this is obviously a bit of a bodge.
This is the first derailleur I've installed so I assume I've done something wrong. Could chain length be an issue?
Thanks for any help you can give,