(1) How are handlebars made? Do they start with a piece of metal pipe and bend it to a precise shape, and if so, how do they relieve the stresses introduced by bending? How do they make the clamp part of the handlebar thicker? On old handlebars, it's obviously a sleeve added on to the basic shape, but what about newer bars which just bulge smoothly in the clamp area?

(2) Why are spoke nipples made of brass? All other highly-stressed threaded fasteners are steel on a "typical" bike, and almost everything else is aluminum. So why brass for spoke nipples? My best guess is that it has to do with corrosion in some way.

(3) How do they put cartridge bottom brackets together? I spent a while staring at a Shimano UN72, and for the life of me, I can't see any seams or joints on the shell. On the other hand, on the Nashbar cartridge BBs, the bearing cartridges are clearly press-fit onto the outside of the shell.

(4) Is there any way to repair inner tubes with cuts right next to the valve stem? I have about 10 of these, and would love to know if there is a way to fix them...

(5) What kind of wrench fits a four-notch track lockring? I own a Park lockring hook wrench, and neither end fits a track lockring. I used the old mallet-and-punch trick to tighten it down.