My primary road bike is a Trek Madone, 43cm with 650 wheels, effective top tube of about 48cm IIRC. I am very short, shy of 4'11". The stem on that bike has next to no rise that I can see and it measures from center bolt of the headset cap to the center of the handlebar slightly less than 60mm. I assume it is a 60mm stem.

I recently bought a used Terry Symmetry (44cm, 650 wheels, effective top tube just short of 50cm IIRC) as a bike I can ride anywhere and park anywhere and toss on the bus racks, that kind of bike. The Symmetry is slightly too long in the reach for me as compared to the Madone. I will say it is a nice and stable bike and not near as twitchy as the Madone. I measure the stem at 70mm. I would like a shorter stem to bring in the reach a bit. I am riding both bikes with the saddle about level with the handlebars.

Questions:

How short of a stem can you go without a big negative on handling?

Neither the Madone nor the Terry have any angle to speak on on the stems. If I get one with a certain amount of rise, does that change effective stem length? Or, is stem length measured differently if the stem is angled?

Unrelated to the stem question, I have another minor question. The tires on the bike are 650 x 28, made by Terry. I like the wider tires. The side of the tire reads inflate to 110 but doesn't give a minimum. I put 90 pounds in them. Can I go lower? I weigh about 105 pounds.