Originally Posted by
smasha
In my case, based on parts availability, it's either:
a) get the gearing not low enough, with 175 cranks
b) get the gearing possibly a little too low, with 170 or 175 cranks
Until the bike is built, and I ride it up and down some hills, I can only make educated guesses about what's "best". After that, then I can consider different cassettes, chain-rings, etc.
Accounting for the pragmatic consideration of parts availability, and if not getting "the best" gearing, at least getting "the best" starting point to make adjustments from, I think option "b" is looking good.
It doesn't have to be a trial and error process. Decent drivetrain components are not exactly disposable. The drivetrain you are settling for gives you a 98" top gear. It kind of works. A nice change from the usual ridiculous 113" top gears ... but ... you can do better. I can just about cruise in that on level ground! It would be spun out in any significant tailwind and any downhill worth calling it that. You are right about the 42T big cog. That's for a 1x drivetrain. With a triple you don't need such a monster bailout gear. The 36T gives you around 16" with the 22T granny. Almost too low to balance, but you would use it once you get used to it. The 18" with the 22Tx 32T just above it works better as an ultimate low. My cargo bike has that combo. I use it a lot.
Going to your alternate 44/34/24 is better. Now your top gear is 108" and with 36T, your bottom gear is 18". Schweet. I'd ride that ... but you can (still) do better: <drum roll> 42/32/22 x 11 - 36. 104" on top and 16.5" on the bottom. What's not to like? And there isn't any magic about 10 teeth between chainrings. You could do 44/32/22 for a bigger top end and still keep the ultra low 16" for those all day long climbs with a load. You haven't even begun to tax the capabilities of modern derailleurs with the drivetrains we have composed thus far. I guarantee if you build the 42 (or 44)/32/22 x 11-36 that you won't be looking to swap anything. 170 vs 175 is a wash. I have bikes with both and I couldn't tell you which has what.
I can't believe with some looking around that you wouldn't be able to find the parts to build this drivetrain. Right now. Hell, go to a bike co-op and get some used rings to tide you over till you can do it right.
Edit: I don't think there has been any mention of wheel/tire size in this discussion. It almost goes without saying that I have been assuming 700C. But I think now is a good time to get it on the record.