In the on going guest of repairing crap on my bike. I'm need of a new stem. Right now I have an adjustable quill stem, but I'm open to going another way. I need to know what I need to measure in order to source a new part. ie [do i measure the exterior of the tube, the circumference what?]
Rans Enduro Sport, Hase Kettweisel Tandem, Merin Bear Valley beater bike
The first thing to check is the diameter of your stem where it goes into the steerer tube. Hopefully it will be 22.2mm. If it measures anything else, you're pretty well screwed relative to finding a replacement.
The second issue is reach. This takes a bit of imagination. It's the HORIZONTAL distance from the center of the handlebar clamp to an imaginary extension of the centerline of the steerer tube.
The third issue is handlebar clamp diameter. Most flat bars are 25.4mm, most dropped bars are 26.0mm.
Finally there's height. People like to talk about how easy it is to adjust handlebar height with a quill stem, but most can't be adjusted very much. If you like a high handlebar you pretty much need a Nitto Technomic. That'll give you about 5 inches from the top of the headset to the bottom of your handlebar. Most stems will restrict you to about 2 inches.