Bacciagalupe

I picked up a vintage bike from a shop this week: Novara Strada, steel frame, downtube indexed / friction shifters, double chainring bike. I think it's 80s era, looks like it was an entry-level road bike, e.g. there are no braze-ons for racks on the seatstays. It rides very well, so I'm guessing it sat in someone's basement for a few years. My main purpose for this bike is for long distance rides (i.e. centuries, ultras), so I think the steel will work out very well.

I noticed that the gearing is kind of high: 52 -42T "Biopace" chainrings, looks like a 12-28 in the back. By my calculations, that's a gear inch range of 40" - 112". I usually run closer to 30" on the low end, but that's with a hybrid bike with very wide tires. So far I don't mind the Biopace, although obviously I haven't put many miles on it.

Also, the tires are mixed -- 700c 25 in front, 700c 28 in back.

So, here we go with the questions....

1) What are my options for lowering the gearing, if it turns out that is necessary?
2) Would replacing the Biopace chainrings require swapping out the cranks as well?
3) Is mixing the tires per this setup a good plan, bad plan, not important?
4) Will going up hills with a 40" low gear make me, like, macho?

Thanks....
B

John E

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.

Generally not, unless you have a nonstandard BCD. However, I have seen Biopace only in 110mm and 130mm, so you should be fine.

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.

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.

GCRyder

1) Larger cog rear, smaller chainring front. You didn't say whether it has a freewheel or a cassette, but larger versions are available in either, up to about 32-34 teeth. If your RD accommodates the 28, it will probably handle 32, at least. Can't say whether that gets you more or less than you could get with a chainring switch, because we'd need the particulars on your cranks to know that.
2) Probably not. You don't mention what crankset it has, but if it has Biopace, it is probably a Shimano with one of their vintage standard BCDs - 110mm for mountain cranks or 130 for road. Lots of round rings available in those sizes. 110 has since become the "standard" for "compact" road setups, which gives new life to the older Shimano MTB cranks.
3) Mixing tires with slight size differences like that is no big deal. When people do it, they almost instinctively put the smaller tire on the rear, like on muscle cars. Many bike gurus, however, recommend putting the larger one on the front. What you're running is an insignificant difference, anyway. Some manufacturers "25" is larger than some others "28."
4) I have a couple of roadie buddies who would tell you without hesitation that 42x28 is already way into wimp territory. They would rather go through rounds of knee surgery than have anyone spot a 23 cog in their rear clusters.

Bacciagalupe

Sweet I didn't think the tire setup would be an issue, and it rides pretty well anyway. I assume speed-wise the difference between 28 and even 23 are not noticeable to a non-racer.

FWIW, I like to spin rapidly on hills. I'm not worried about looking like a wuss by some random cycler who's staring at my gears, I'd rather just make it up the hills.

- I'm pretty sure the cranks are 130mm. How do I verify, just by measuring?
- Any issues mixing a Biopace big ring with a round regular ring? Or should I just swap both at once.
- I can't tell if it's a freewheel or cassette.
- What's the max jump on the front -- 14 teeth, correct? I.e. if I tried to go for a 50/32 compact, I'd need to swap out to a 110 crank.