I wish i could say it was my own idea, but plenty of others have done this. I got the deepest-tread knobby tires i could find (pyramid $30/pr), and got a bunch of #8 X 1/2" lath screws with super-large flat heads for $5 . drilled (using a very small bit) down from the center of chosen knob into the tire. drilled screw up from inside-out. if your angle isnt pretty correct, it'll stick out one side or the other. be prepared to have plenty of time to do this...its tedious and time-consuming. dont try drilling all the holes, then installing screws...you'll drive yourself bat-s**t, trying to find which knob you drilled. i thought about the side-to-side play, and the screws wanting to push back into tire. thats why i opted for the lath screws....really flat and alot of surface area. with two tire liners taped side-to-side, getting the tires mounted on the rims was a nightmare. ive never actually wrestled a rabid porcupine, but i think i know what it feels like. rode today, and THESE. KICK. BUTT-CHEEKS!!! our driveway is pretty long, up to the pavement. packed with snow/ice, and they performed very well. i went off a little into some deeper powder, and the rear did slip sideways just a little bit under power. going to have to swap out my 36tooth for a 44. i havent ridden on dry pavement yet, because i'm scared.