Originally posted by SDS
Mark, I wonder if you could give us a loaded rollout figure for some of the 26" tandem tires with road treads? I think my 700 X 32's are about 83.5" for the front, with me putting as much weight as I can on the tire during the rollout. Occasionally I hear grumbling coming from the back that the 53 X 11 is not a high enough gear...
I can't speak to the actual roll-out numbers as I don't have any point of reference in our fleet. All we have are 700c roadies & 26 knobbies. However, there are only minor differences between the label diameter and roll-out when it comes to actual speed.
There are some links to gear calculators where you can punch in the various gear combinations and stock tire sizes in various widths to come up with tables that you can compare to your current set-up.
For example to get the same 130 gear inches that you get on your 700x32's with a 53x11t set-up you'd have to run a 60t chain ring on a bike with 26" X 1.0" (25-559) tires. If you're just thinking about upping your front chain ring to a 54 you'll get another 2" of travel per pedal stroke which is barely noticeable.
We usually run 54 x 12-27t with 700x23 or 70025 tires for about 118" gear inches and spin-out at about 45 mph. Back to Rick's potential set-up, a 56x11t set-up on a 26" bike would put his big gear in the 124" range.
Here is a link to Sheldon's calculator; it's probably all you'll need:
http://www.sheldonbrown.com/gears/
There are others out there; just use this google search string:
http://www.google.com/search?hl=en&i...=Google+Search
P.S. Sorry, I had to leave in the middle of composing this reply.