Siping/grooving/cutting is a subject for OFF ROAD performance only. Yea, you can use a razor and get better wet-on-road traction.

Off Road: You'd only want to experiment with "custom" tires after trying the many good off road tires available. All tire "customising" is a compromise for different conditions.

If you love the mud, go crazy with the heat knife on some tread patterns. For sand, some "siping/slicing" may help on the rocks for flexing and conforming to obstacles. nless you have really tried the after-market tires out there, kept the knife in the drawer!

Can this make difference with MTs??

Many people sipe their tires up here for winter driving on ice. You can sipe MTs,though with the weight of a Hummer I don't know if it's worth it, especially if you use them year round, because any off-pavement driving will eat them up. If you drive siped tires on ice do not run your tire psi low.

What's interesting though, is that siping helps lengthen the life of the tire, so I'm told (if you drive on pavement). A lot of wear is due to heat from the tire and ground which softens (or melts) the rubber and creates more wear, siping allows air between the large lugs and cools, lengthening the life of the tire. How much? I don't know.

For mud, the TSL/Bogger; Ground Hawg; or the Gumbo Wide Mudder. You don't need to sipe these. They do not come in 37 12.50 16.5, but you can find them a little bigger or smaller.

Goodyear guys say the GSA works better on ice then the MTs. I haven't noticed a difference.

Dan Astrom