Originally Posted by
spinconn
I agree, my question was basically just what other geometry specs might come into play, other than reach and stack.
Not really much if you are looking at a true road bike. The seat tube angle might be a little slacker for a road bike that is considered a touring bike. The ones you use for multi-day trips loaded to the gills. If the seat tube angle is extremely slack, then you probably aren't looking at a real road bike, maybe more of a cruiser. Or if it's gone the other direction and steeper, then you might be in TT bike territory.
You can also look at reach from the perspective of Effective top tube length, but consider that the STA on most of your road bikes are going to be within a few fractions of a degree, frame stack will give you a relative number to compare all by. Some makers still don't give effective top tube length. The only difference is it's measured horizontally from top of head tube (generally there'bout) to the seat tube, and frame reach is horizontally from the BB center to the top of the head tube.
Check the bar reach and stem reach though. Especially between different models and brands. Many give the stem length and even bar width on geometry specs now, but for bar reach you'll have to look them up from what bars are spec'd in the description. And all those reaches add up. As well I found the 42 wide bars on the smaller size bike annoying. So I bought some 38cm wide bars and am annoyed no more. Even seem to improve the feel of handling for twisty and fast down hill turns.
As well check for crank length changes if you are considering more than one size of bike in the same model. Too long a crank might be annoying. It's one of the big reasons I didn't choose a 58cm Tarmac over the 56cm I bought. I'd think you'd get use to a shorter crank, but maybe not.
All the other changes in geometry will just be handling perception changes that you'll either like or will get use to. So not so much for fit, but possibly for particular type of cycling you do or terrain and road surfaces you ride on they might be something. But those will even more of a marginal gain type thing for any discussion to get heated over. <grin>