Originally Posted by Bacciagalupe
1) What are my options for lowering the gearing, if it turns out that is necessary?
Check the bolt circle diameter (BCD) of your cranks. If it is a road-standard 130mm, you can drop your lowest gear by 10% simply by replacing the 42T Biopace with a round 38T ring. If it is mountain-standard 110mm, you can go even smaller -- 34T, if I recall correctly.
Originally Posted by Bacciagalupe
2) Would replacing the Biopace chainrings require swapping out the cranks as well?
Generally not, unless you have a nonstandard BCD. However, I have seen Biopace only in 110mm and 130mm, so you should be fine.
Originally Posted by Bacciagalupe
3) Is mixing the tires per this setup a good plan, bad plan, not important?
It's not important and makes a modicum of sense, because you put more weight over the rear. Also note that some models of 28mm tires are narrower than certain other 25mm tires.
Originally Posted by Bacciagalupe
4) Will going up hills with a 40" low gear make me, like, macho?
I typically gear my bikes with seldom-used lowest gears in the mid-40s, e.g. my preferred 44 gear-inches (42/26) on the Bianchi and the UO-8, and a slightly higher 45" (38/23) on Capo #1. I get ALOT of use out of second gear, which is typically circa 49" (42/23 or 38/21), about 2% below a typical Tour de France grannie (if one can call it that!) of 50" (39/21). I expect to resort to Capo #2's lowest gear, an "I hope I can still handle this as I did 30 years ago" 48-incher (46/26), fairly often. On that bike, I am constrained by the 6-bolt 157mm BCD (44T minimum) and the original 1960 Campagnolo Gran Sport derailleur's 26T low-cog limit, and I am not even considering retaining the knee-busting stock gearing of 52-48/14-16-18-20-22 (59 to 100 gear-inches; the bike was made in Schwarzenegger country), which one of my friends still has on his.