Moped Army

There are perfectly-acceptable ways to make your own.

The best (and also the most gut-wrenching) is to install big knobbie dirtbike tires. Then, screw short, dull sheet metal screws into the _knobs_ and cut the heads off at an angle.

That reportedly works as well as a manufactured studded tire (that's how studs work, basically), but it gives me the willies.

For bicycles, the accepted method is to work a screw through the inside of the tire (through a knobbie, still, if you've got them) and then use a thick rim strip between tire and tube to prevent you from puncturing the inner tube (like you described).

An old tire with the bead cut off works incredibly well as a rim strip for this purpose - you can even find one that fits as a loop (I've used old-style 26 by 1 3/4 inch tires as rim strips for modern 700c wheels that I then studded).

The side-advantage of running with an extra tire crammed into your wheels is that, if you do get a flat (which is easier when you're running tires at a really low pressure), you can ride on the flattened tire fairly safely - you chew up your tube, but the extra tire protects your wheel.