Don't beat up too bad...I'm pretty new to the biking thing. Just bought my first road bike, a Jamis Renegade Expat. I like to fool around with things and I'd like to shorten the reach. I want to go shorter with the stem to a 90mm. My question is what size stem do I need for this bike? A 31.8?

Thank you.

The specs say that you have a Ritchey bar 31.8mm. So a 31.8mm stem should fit the bill.

renegadeexpat

Nice bike, BTW.

You can also measure the handlebar diameter where the stem clamps, most likely it is 31.8. Other common sizes are 25.4 and 26.0.

Well stems actually have a few dimensions that one should at least know about besides the clamping one. First and second are the steerer and the bar clamp diameters. Measuring these (especially the bars) can be hard if you don't have a caliper on hand. But if you do a careful circumference measurement (by taking a strip of paper, wrapping it around the bars and then marking across the start and finish of this strip) and divide by 3,1415 (or 22/7) you get a diameter. Next is the extension length, which you stated by the 90mm reference. Do know that this is usually done fron the center of the extension and the steerer/bar intersection points. This is not the same as measuring along the top of the stem. (A very common mistake to make). Almost last is the angle that the extension makes WRT the steerer. Be awear that some companies measure from the steerer and others from a perpendicular to the steerer. And last is the steerer's clamp height. A stem with an extension raising at a steep angle needs more steerer clamp height to have the extension contact the clamp section fully. There are times when one will have to remove a steerer spacer or two to allow the stem to fully clamp around the steerer, this can place the bars at a lower height then simple math might initially suggest.


So once again we find that a simple question really needs a long and involved answer to be fully understood. Andy

On the handy website linked below, fill in the stem dimensions of the two stems you are comparing and it will tell you the change in bar height and reach.
Stem Comparison Tool | yojimg.net

REally cool tool. Unfortunately it doesn't take into account my last point about he change in the stem's steerer clamp height/length as the extension angle raises. But again a cool device to start with. Andy

Thanks. Got the info. I needed!