So I want to do some updating on my old steel frame Bronco Rocket mtb and change the stem and handlebar.
The original stem is welded to the fork stearer as it comes up through the head tube on the frame. What do I need to keep in mind when purchasing a new stem with an attached fork bearer - do I need to know the diameter of the head tube? Can I use a stem like in the figure?
I would suggest reading this: http://www.sheldonbrown.com/handsup.html especially the part on stem/fork and stem/handlebar compatibility. Then buy a cheap caliper to measure you parts and see what size you have. (I got a caliper for ~$10 at Sears)