How big a difference do I need to worry about for stack and reach?
Looking at several bikes for my first road bike. Aiming for under $1200 here. Primarily for commuting(tired of fighting a 10+mph average headwind on an upright 'sport comfort' bike), but fun/long fitness rides are a priority. So is trying to get faster.
I'm looking at several bikes, most new, one used. I'm wondering how wide a range of stack/reach measurements have to be until they become significant enough for a bike to not fit.
At a LBS, I spent about 30 minutes total across two bikes. I honestly couldn't tell the difference between the two. Both were surprisingly comfortable, for completely unfamiliar positions. I suspect I would adjust pretty quickly and easily to a more aggressive riding position. I doubt I could tell a difference between the two, barring pain schemes.
For the ones that list stack/reach:
Bike #1 is a 58cm: Reach of 39.1cm, Stack of 59.8cm. 58cm frame.
Bike #2 is a 60cm: Reach of 39.5cm, Stack of 61.5cm. 60cm frame.
I recently saw a Bike #3 I would potentially buy used. It's also a 58, with a Reach of 40.3cm and a Stack of 58cm. Top tube length right in the middle between #1 &2, lower stand over than both-which appeals to me. It's a higher quality bike with much higher quality components, but lightly used and 4 years old. 8-12mm doesn't seem like much. Easily fixed with a different stem, if necessary, right? And the shorter stack would just mean a more aggressive fit? Or are the differences of #3 vs 1 or 2 severe enough to not be comfortable?
Several other bikes I found enjoyable to ride felt different than 1&2, but didn't have any stack/reach listed, so I expect that I'm not too picky/discerning. Just don't want a case of buyer's remorse.
The stack of 58 cm means your handlebars will be at least 2 cm lower than on the two new bikes, and the reach 1 cm longer means you will reach out farther. You can adjust actual hbar reach by putting on a shorter stem, and you can adjust actual hbar drop by adding spacers under the stem or using a more angled stem in the "sticking up" position. Some people think a stem sticking up looks ugly on a road bike, but YMMV! Another degree of freedom is a narrower bar or one with shorter reach.
You might or might not be able to get a stem that will achieve the fit adjustments you might want. Unfortunately I don't think I could analyze this for myself without buying the bike and trying it out.