I too noticed the tab - it used to be bent a few degrees more than that, so I've already bent it a bit but any more and I start to deform the hole and the screw won't screw in.
I've owned the bike since new (early to mid 90s). So it's the original b screw
Screw isn't all the way in the photos because I ve been adjusting it in and out as I've been trying to diagnose, but it has no impact whatsoever on the hanger height when the chain is on. Whether it's all the way in or all the way out - no difference
The chain tension is pulling the derailleur forwards, but 'forward' in my sense is pulling the b-screw with greater force to the frame (as opposed to away from it).
I'm not sure which part you mean. I'm going to try and take some close up photos....
There is only one hole in the knuckle spring - so no option to vary there. In the tension spring, there are two 'available' holes close to one another, and two 'unavailable' holes almost 180 degrees away. By 'available' I mean that the hanger has the four holes, but the disc that the spring fits...
It's all the original kit that came on the bike when I bought it new so I assume that it is designed to go together. I haven't ridden it for 20 years, but I reckon I would have spotted it back then if it had been ill configured. So I think it used to be fine.
The other thing that cones to mind...
I've got an Exage 400LX rear derailleur and the jockey wheel is essentially running directly on top of the largest gear in the rear cassette, so I need to increase the gap.
Screwing in the B-screw seems to have no effect when the chain is on. The end of the screw is making contact with the...
... very, very dry at the moment though - so still don't know whether clearance will be a problem in muddy conditions. (new tyres are 2.25 inches, original ones were 2inches, frame is probably a fair bit narrower than modern bikes)
Went out on the bike yesterday for some very light trail riding and was delighted with the bike. The Nobby Nics feel so much grippier than I remember the original mavrics. And they feel like they roll better on tarmac too. Another huge difference (possibly even more profound) was the pedals. I...
Thanks for all your suggestions. Shortlist came down to Nobby Nics and Panaracer Fire. I've taken the risk on clearance and gone for Nobby Nics because they have had more iterative innovations giving me the feeling that they might have the upper hand in performance, technology, and execution. If...