If you want 12 speeds without spreading the frame or changing the rear hub axle, you could use an old SunTour Ultra-6 freewheel. These fit 6 cogs into a width only very slightly wider than a standard 5-speed by reducing cog spacing. They worked OK with Regina chains, but better with Sedis. I used these a lot at one time. As others have stated, the smallest ring for an NR crank was 41T. Genuine Campy are a bit rare, but I have used the TA 41T ring Sheldon speaks of and they are very nice. I have gotten a 41-28 combo to work with an NR RD buy getting the chainlength just right. I've never gone to a 42-31.
Regards,
Jerry Moos
Houston, TX
> Lets say hypothetically I just scored an early 70's(#173538) Mondia
Special
> with NR derailleurs.....
>
> ---What is the widest possible (10 or maybe 12 speed) gear range I can get
> sticking with the Campy hubs and crank set and derailleurs?
>
> ---What is the smallest available ring that will fit the inside bolts and
> still not require more chain-wrap than the r/d NR will accommodate?
>
> I have long cages and triples on everything else but I'd like to keep this
> Mondia close to original. I'm trying to get some more mileage out of these
> knees before I'm forced to consider replacement.
>
> Calvert Guthrie
> Kansas City