Niles Michigan? Hello neighbour! How's Lake Michigan?
I don't know the diameter offhand but here are some considerations before you replace the stem.
- a metal (aluminum) stem will be a bit lighter than traditional rubber
- you can purchase them in colors, if that suits your taste
- you can also get 90 angled stems which may ease inflation for you; especially on the front, whenever you get around to replacing that one
FWIW; I've always put a bit of silicone around the nut (inside of the wheel) securing the stem to the wheel as a bit of insurance against very small air leaks. Obviously, let the silicone cure before mounting the tire.