Frank Berto in his early 1980's article listed your NR max cog teeth at 28. I think just about every other short cage derailleur was listed at or about 28 except for a Suntour which was listed at 29 or 30 if I remember. Hey everyone suffers on the hill whether they have a 39 - 32 and suffer because they go slow and get passed, or a 42 - 24 because they feel stupid, are about to burst and pass out but get stronger legs and lungs (eventually).In South Florida I do our biggest hill in 42 -18 but the pros seem to favor 42 - 15 (then why do they have 11-19, 9 speed clusters on the back if they are not going to use them??) Garth Libre in Surfside Fl.