Stud
This is what I do. Use screws that measure 1/2 inch in length with a 3/32 shank hole width, stainless steel, countersink screws, available at any hardware store. Use a tire with large flat knobs. These will help to support the studs and prevent them from rolling over on hardpack. Pre-drill holes in the tire from the outside in, in the center of the flat knobs, using a 1/16 bit. This will ensure that the screws go in straight and end up where you want them to on the outside. Screw the screws in from the inside out, don't overtighten the screws, if they spin too much once they are flush with the inside of the tire they will just chew up the rubber inside the hole and won't hold as well. I put a drop of superglue on each screwhead where it contacts the rubber, I believe this helps in keeping them secure, but my riding partner skips this step. Neither of us have had any problems with the screws coming out. As the prev-poster stated, cut an old tube and use it as a tire liner. Inflate and enjoy. You may have to downsize your tire of choice due to the extra clearance needed for the screws, I use 1.95's. The screws

will ruin a paint job if they hit your chain/seatstay or frame/fork. Don't ride these on the street, it will dull the screws and cause the screws to rollover, this is the only time I have flatted one of these creations. Have fun...