I acquired an NR rear derailleur that looks like it hasn't been cleaned since it was manufactured. In particular, the knurled spring cage cover is stuck and won't rotate around the lower body. Is this a common problem with this design? And if so, is there a recommended resolution? I'm thinking of trying some PB Blaster and gentle persuasion to see if I can work it loose.
I'm also wondering why there are two holes in the spring cage cover for the pin on the tension spring. Is this simply to adjust for loss of tension in the spring? Or are there specific applications for each tension setting. And finally, what's the purpose for the grub screw on the spring cage cover?
Thanks,
Bob Chmara
Southfield, Michigan, USA