Stem Size?

What is the shortest and longest that you should go to get the optimum fit? Without seeing arm size and torso and what not. Just a general question. You wouldn’t want a 70mm or a 150mm would you? How about those ones with a rise that is almost 90degress straight up! Those seem to be the wrong size. Why risk injury or crashing? What is the ideal size no matter what.

It almost seems like this would be as general as crankarm length.

Start with stem length, crankarm length and then build the rest of the bike around those two things. Then you would get the right size fram by default and seat height would be somewhat of given. Then you would have a bike? Seems pretty easy but unfortunately its not.

Hey Matt, good questions and observations. In general, going to a “too short” stem causes steering to become too responsive, the steering lever is too short and the bike has an odd “unstable” feel to it. Gary Fisher bicycles has actually harnessed some of this through there “Genesis Geometry” on mountain bikes where the top tubes are relatively long (compared to other brands) and the stems are shorter making the steering feel distinctly different. Whe the stem is “too long” (140mm+) the steering seems to go a bit “dead” where you have to move the handlebars a lot through their arch to get a little steering effect. the bike is “too stable” and not responsive enough. Your second insight on building the frame aroung the cranks and seatpost is not far off from Ernesto Colnago’s fit philosophy as described to me by Dave Koesel, formerly an employee (or independent contractor as a rep) of Trialtir, the U.S. Colango distributor. Dave showed us how Colnagos were designed to use longer stems (120-130) to acheive optimal weight distribution and handling. I can attest to the effectiveness of this. I once owned a Colango only 1cm too large and the following year bought a less expensive Colnago 1cm smaller frame size. The 1cm. did make a noticable difference for the better. I still have that bike. So I think your assumptions about building around stem and cranks are not too far off.

it looks like Tom did a wonderful job of not actually answering your question :slight_smile: kidding tom

I’d say a stem length ranging from 100 to 130mm and no more than like 6-10 degrees of rise.