Let all the air out of your tires and find somebody who knows how to run a skilsaw, decide how wide you want the grooves and sandwich 1 to 3 blades(old carbide) 1/16kerf, more might be ok I don't know. Ideally they should be the same type and size. Set your guide to the desired depth. Again, if you aren't good with a skilsaw don't attempt this. I will accept no responsibilities for amputations and injuries that occur. BE SAFE! Wear full goggles and face shield and ear plugs. Small rocks imbedded in old sipes will fly with bullet like force. I hawged out an old set of M/S bias ply tires once that the iron wouldn't touch. It still takes a while to do all four but works good. You also can get carbide bits that go on grinders from the tire pro's for a little more control. Mark out what you want before hand too, it is easy to get carried away.