Ted said:Yes, I would probably use a medium length cage derailleur to take up
the chain. I know there are other people out there using large
chainrings(56+) on Bike Fridays but I'm not sure which derailleurs
they're using. I was thinking of modifing a 11-23 cassette to a 11-25
which would give me a low gear of about 24 inches.
Use the LONG cage Campagnolo rear derailleur. Campagnolo makes short,
medium, and long cage derailleurs. The LONG version will most likely
wrap up enough chain to use the bigger cogs in back with the inner
chainring.
I met a guy with a truss frame Moulton who ran 10 speed Campagnolo.
55-39 chainrings with 11-29 cassette. You can get Veloce loose cog
cassettes and mix up the cogs. Or use a riveted together cassette for
the first 6-7 or so cogs and then loose Veloce for the upper cogs.
Given the fact Moultons are about $5,000 plus for the truss frame
model, buying two cassettes to get one isn't much of a concern. This
guy used a Dura Ace triple front derailleur and a medium/long cage
Campagnolo rear derailleur. Record 10 speed shifters.
32x23 = 25 gear inches
30x23 = 23.5 gear inches
32x25 = 23 gear inches
Might be better off just using the stock 11-23 cassette and going with
a 30 tooth inner chainring. Chain length will be shorter with the
56x23 combo than with the 56x25 so the derailleur will have less to
wrap. But you may lose the use of one of the smaller cogs on the
cassette because the chain droops too much. And the chain may rub the
bottom of the front derailleur cage if using any but the biggest cogs
due to the 30 ring being a little less diameter and the fact the front
derailleur is mounted so high to clear the 56 ring.
I'd suggest trying the 11-23 stock cassette first and judging if
changing to a 30 inner chainring will present any problems.
