Marc,
This is a recurring theme, but I've seen NR derailleurs pushed to 42/52 x 14/30. Some will claim this is not possible (I believe there was slack in the typically unused 42 x 14 combination), and others will claim that they have seen NRs pushed to even greater limits.
Personally, I have found that 42/53 x 13/26 is the true limit for decent performance without causing undue stress. It's the max that the NR is truly happy with. Even so, I have set up many a bike with 28t cogs in the back. The trick is in getting the chainlength just right and the wheel in the right position fore and aft in the dropout. I always insist that the large/large combination be possible without trashing the rear mech. The biggest problems to watch out for are the chain not coming back off the big cog once in, and that you have sufficient space between the cage and the spokes. With old-style Atom and Regina reversible cogs, you may have to grind the inside of the teeth to create an edge that will catch the chain, creating a profile more like that of a Japanese FW.
Steve Barner, Bolton, Vermont
> Date: Sat, 13 Nov 2004 06:10:37 -0800 (PST)
> From: marc garcia <marcgarcia80@ameritech.net>
> To: classicrendezvous@bikelist.org
> Subject: [CR]gear limits of a 71 NR rear derailleur
>
> I decided to build up an old trek frame I had with some campy parts. I
used more of a touring freewheel but the NR derailleur doesn't seem to be
able to handle the larger cogs in the rear when the chain is on the small
chain ring up front. I've always used one step racing type freewheels with
campy derailleurs and I've never encountered this problem before. when it is
in the gears stated above the pulley hits the freewheel. are these
derailleurs just not meant to handle such gear ratios or do I some how have
this set up wrong? what are the gearing limits for these?
>
> marc garcia
> chicago IL