I think ~3/4" in the rears and smaller in the fronts, well short of the lug depth anyways! I wouldn't use these in the woods in the winter as spinning and gripping one on a root would probably rip it out, but they seem to stay in very well on gravel and ice. It's best to put them in when the tire is warmer but I have put them in, in -5C as the driveway was pure ice!Thanks for the screw suggestion I never considered that although it brought back a 60 year old memory we used to do that to out dirt bike tires in the winter to go tear up frozen ponds, those were the days. What length screws do you use?