I wanted to run some geometry numbers to see if that might help us with more of an "educated guess".
I've got experience with 2 bikes and they both fit me quite well. However, I wouldn't want to go bigger than them and I suspect a slightly smaller size would work as well. here are the stats on them:
59cm Kona Paddy Wagon:
- Seat Tube length (sloping top tube) 57cm
- Top Tube length 585cm
- Reach 410cm
- Stack 572cm
59cm Surly Steamroller:
- Seat Tube length (flat top tube) 59cm
- Top Tube length 587 cm
- Reach 408cm
- Stack 586cm
Both of the above bikes have a similar reach. The stack is longer on the Surly. Both bikes seemed to work for me from a size perspective after adjusting stems to adjust length and height slightly.
Now, with the two Jamis sizes (21" and 23" I'm considering)
21" Jamis Coda
- Seat Tube length (Sloping Top Tube) 53.3cm
- Top Tube length 585cm
- Reach 412cm
- Stack 583cm
23" Jamis Coda
- Seat Tube length (Sloping Top Tube) 58.4cm
- Top Tube length 595cm
- Reach 418cm
- Stack 598cm
It appears that the 21" Jamis has a similar Stack and Reach to both the 59cm Surly and Kona that worked well for me. The 23" Jamis has a longer Stack and Reach than both the Kona and Surly. This causes me concern that it could be too big for me and have me stretched out too much.
The thing that is causing me some confusion is the Seat Tube length. It's quite a bit shorter on the 21" Jamis vs the Kona and Surly. Even if we disregard the Surly because of the flat top tube, the sloping top tube of the Kona at 57cm is still 3.7cm longer than the 21" Jamis.
Would this shorter top tube perhaps suggest that I would get more of an "upright" riding position because the seat is lower but I can still get the same reach and stack? If so, I'm ok with that as I've had a back surgery in the past and would prefer to be more upright.
Again, I know this isn't the best way to buy a bike at all, but there is no chance for me to test ride one of these and the prices good enough that I'm will to take a chance with some help to make an educated guess.
Thanks
James