Hi all - I spent last summer dialing in the fit on my touring bike, which I have had since it was unboxed at the shop I worked for in high school. After all the fiddling, I think that fit is pretty good (if only I could stop thinking about it, I'd probably be happy!), but the esthetics of the situation is less pleasing. As seen here, my 1986 23" Schwinn Voyageur:
Note the extend stem with a 40mm reach. Blech. The Voyageur is 23" ST (c-t) and 22" TT (c-c), which is basically as small TT/ST ratio as one can find in a production bike. So I take this as the perfect excuse to finally build that frame I've always wanted.
Moving onto design, I've been playing with CAD, BikeCad and this guy:
https://www.bikegeocalc.com/ to come up with a frame which with the same fit, but will allow a 6deg, 80mm-ish reach stem. This was chosen because it (a) looks pretty good to me, and (b) gives me 40mm more room for adjustment, and (c) even more options with varying stem angle, and (d) pushing beyond 40mm will make the concerns below more concerning.
Drawing up the designs with the 80mm stem, the geometry which results has me wondering about the relationship of front-center, HTA, fork offset, wheelbase and everything else. More specifically,
wondering how much I should be wondering about this stuff. I would appreciate any thoughts on my musings below.
For reference the Voyageur is:
HTA/STA: 72/74
WB: 1051
FC: 613
CS: 451
Rake/Trail/Flop: 50.8/62/18
Primary objective: I need to shorten my reach about 30mm, and I want a flat top-tube. So to get there we need to shorten the TT and/or lower HTA which will impact FC and WB.
Some options (using 50.8 rake, because this is what I have, and this seems to be middle of the road in touring bikes):
HTA 72 = 583FC and 1021WB, 60Trail, 18Flop (I'm converting to 700c from 27)
HTA 71 = 593FC and 1031WB, 67Trail, 21Flop
HTA 70 = 601FC and 1041WB, 73Trail, 24Flop
I am aware of toe overlap, and I already have it with my fenders at the current 613FC, but it doesn't bother me, so not a deal breaker, but I'm wondering if any of the above tradeoffs should be considered critical? Specifically, all the above HTAs are within the realm of the popular touring bikes smaller frames (LHT, 520), but the WB will be 20-30mm shorter. Is there anything in the ratio of CS:FC which would cause trouble?
How about converting between any of the above choices with a fork change? I can adjust trail/flop by offset for a given HTA...are the fork parameters going to be more important. Bike with a HTA 72 + 60Trail going to feel like a HTA 70 + 65Trail, all other things equal?
Is there anything else I'm missing? Is it reasonable to cut 30mm reach out of a nice touring bike and expect the result to also be nice?
Thanks for any thoughts. I know there are lots of experimenters out there who have probably done similar things, so I'd appreciate any input.
Don