Groovin' On A Sunday Afternoon
Or Tuning Your Tires For Traction
By Jack Brinks

Grooving off-road tires has become very popular for several reasons.  Some folks do it to improve side-hill traction, some to improve performance in the mud, and I imagine there’s a few who do it just because it looks cool.  Either way, there are definite advantages to grooving your tires, especially if you run a stiff sidewalled tire, like a bias ply Super Swamper TSL or TSL SX.  The advantage I was looking for was to gain more flex without having to run ultra-low pressures that tend to un-seat tire beads.  Before you start though, remember that with one cut of the groover, you’re sure to void any warranty on your tires, including any road hazard coverage.  

The first thing you have to do is get tire groover.  I borrowed the one you see here, but you can find several different models on the web by searching for “tire groovers”.  This 250 watt model, made by Ideal Heated Knives, Inc. comes with a #4 head (.215” wide), worked just fine for me.  And, it’s under $70 and is available on-line from American Power Sports at www.apskarting.com.  This company actually specializes in go-kart racing.   

 

If you want, you can spend over $400 for a groover, but it’s overkill unless you’re going into the business.  Regardless of which model you choose, don’t forget to order the appropriate size groover heads and blades you’ll need for your plans.    

Once you’ve figured out just how much rubber you want to remove and exactly where you want remove it from, you can get started.  First, install the size head and blade you’ve decided to use, making sure you adjust the blade to the depth you want to cut.  Don’t go too deep, as you don’t want to cut into the tire cord.  Then, plug in your groover to let it get good and hot, and let’s get ready to go!  FYI, make sure you install the blade in the proper direction…it cuts a whole lot better!

But, before we get started, let me warn you of one thing.  Grooving your tires can be addictive!  My original plans were to just cut the center lugs, but I just couldn’t help myself!  After that was done, well, you’ll see. 

Let’s start with the center lugs.  I decided to make 2 cuts in each lug using a .215” wide blade.  My goal here was to break up these large blocks of rubber into smaller lugs which would allow the tire tread to flex more easily and increase sidehill traction. 

Please note that I said tire tread, not sidewalls.  

Place the grooving iron blade against the side of the lug, and apply firm, even pressure.  If you’re going too slow, you’ll get a lot of smoke.  Pushing too hard will significantly reduce the life of the blade.  Take your time; you’ll get the hang of it before you know it.  You’ll probably use at least one blade per tire regardless.. 

The outer lugs are a little more difficult, since you have to bring the blade down into the rubber.  To do this, use the curved tip of the groover head to bring the blade down into the lug at an angle.  As you apply pressure and begin cutting, slowly bring the groover handle to a more level position and finish cutting the lug towards the center of the tire.  If you want, you can cut the lug straight or at a slight curve.  The rubber you’ve removed won’t be too hot and you can pull it out immediately or later, whatever suits you.

The reason for not grooving the entire length of the lug is to reduce “chunking” of the lug on sharp rocks.  Notice I said reduce, not eliminate.  As you can see by the photograph, this lug is almost half gone.  If you look closely, you can see that there was already a crack or a tear at the base of the lug.  In my opinion, the groove allowed extra movement and subsequent loss of the lug.  I believe that if the entire length of the outer lugs were grooved, much greater chunking would occur.  Obviously, this one of the disadvantages involved in cutting the outer lugs.  It may not be for you.    

Just a hint.  I started out with the tires and wheels off my Jeep.  I soon found out that for cutting the center lugs, it was easier to control when they were still bolted on the Jeep.  The outer lugs were easiest to cut with the tires laying on their sides and cutting down towards the center.  

So, did it make difference?  In my opinion, yes!  It’s not one of those things that’s easy to measure or compare, but I definitely noticed several positives and a couple of negatives.  The first negative is the chunking that you’ve already seen.  The other is that the tires pick a lot more stones than they used to and can get thrown like small missiles while driving.  Drivers of open wheeled vehicles should be careful of this.  You can still see a couple stones imbedded in the new grooves.

 As for the positives, it was apparent that there was improved traction on side hills.  Also, I noticed that even at my trail pressure of 9 PSI, the tread area of the tire flexed considerably, allowing much more of the tread to contact rocks, etc.  Notice in the photos that while the sidewall has little to no flex, the tread has flexed quite a bit.  Those familiar with Super Swamper TSL SX’s understand that 9 PSI is not actually low for this bias ply tire.  With beadlocks, these tires are often run at 3 to 5 PSI to gain adequate sidewall flex. 

Would I do it again?  For my application, definitely yes.  On a vehicle that sees the street more often than the trail?  Probably not.  And, keep in mind that while tire grooving works well on biased ply tires, I wouldn’t recommend doing it to radial tires with sidewalls that usually flex well at 12 to 15 PSI.  Either way, it’s up to you.  But for me, it’s groovy!  

Jack Brinks