Most (including the 3 speeds) were plain old carbon steel tubing, similar to millions of other low-end bikes. Lighter than a varsinental, higher quality than other department stores bikes, but not worth sinking a lot of money into fancy upgrades, even for your own use.

I rode one of the reynolds sears bikes once. It handled very oddly, like it had way too much trail -- you had to fight it to make it turn a corner.