A co-worker uses "cold-cutter" screws. I have not seen his work, but he claims they work well. He says he "aims" the screw heads. I helped a guy put sheet metal screws in his knobs many years ago, they were the hex head type. He was an amateur ice racer for fun, and I dont remember if he was competitive. It took a lot of screws. I think there are a few ice racers on this site, hopefully they will reply with better information than I have. I have wondered about all the really cool traction products available for snowmobile tracks and whether they could be adapted to motorcycle tires. Good Luck.