The tire grooving is the process of cutting new patterns into your lugs to make the tire grip, flex and sometimes even wear better.  It's pretty common to see the Swampers with every center lug cut into two so this was the pattern I thought I would try.

The tire groover, purchased from Afco Racing (got it for X-mas).  Basically a giant soldering iron with an adjustable blade attached to the end of the copper tip.  Different width blades are available, I used the .29" one.

It took about an hour and a half to do all 4 of my tires.  Since my tires are pretty worn down with only about a quarter inch of tread depth I cut all the way thru the tread blocks.  With new tires you don't want to go all the way, a quarter inch should suffice.  I let the groover warm up for about 10 minutes.  Since it needs to be held upright when warming up (according to the directions) I clamped the handle in a vice when I wasn't actually using the tool.  The actual cutting was pretty effortless, the secret being keeping the copper tip in contact with the tire ahead of the blade.  This pre-heats the rubber and makes the blade slice right thru.  I did all 4 tires with one blade.

Testing.  I tried climbing this waterfall on the Lost World trail before grooving my tires.  The easier line is to stay high on the rocks like in the first picture but after 5 or 6 tries I could not get the tires to grip.  They were trying to climb both front and rear so the Zuk would pivot around the two obstacles and push the back end towards the big hole at the bottom of the fall.  Eventually I was forced to drive into the hole, which put me in a pretty off-cambered situation.  I had to hook a strap to the bumper with some people tugging on it to bring the body back down and keep it from hitting the rock wall on my right.

I tried the same line with the grooved tires and no slippage whatsoever.  I was pretty surprised.  On the flat surface of the waterfall, the added grooves didn't seem to help and I still spun all four.  I eventually made it to the top by steering to the right and getting the rear tire on the passenger side out of a small depression in the rock.  I'll be running Highway to Hell again soon to see if some of the climbs I had problems with last time are any different.

One downside to grooving your tires is you increase the chances for tread to get ripped off, known as chunking.  These cuts occurred on Intimidator/Upper Firebird.  Actually I am not to sure these cuts would not have occurred even with a solid tread block.  But I have seen people cut their lugs into 3 parts which might be a little too much if you travel over sharps rocks a lot.  take your local trails and rock types into consideration before cutting.