— Testing the new 33×10-15 size tires from STI —
As machine sizes and engine horsepower numbers grow in the UTV world, tire sizes have no problem keeping up. We first saw huge tire sizes in the mud pits, and they have now ended up on high-performance machines.
WHAT IS IT?
The latest size in STI’s growing line of Chicane tires is bigger than what comes on most full-sized pick-up trucks. It has eight-ply construction with 3/4-inch-tall lugs and a slightly rounded profile. The new, non-directional, 33-inch size is available for 14- or 15-inch wheels. MSRP for the 33X10-15-size tires we tested come in at $259.91 each.
HOW ABOUT THE WHEELS?
Modern UTVs, especially ones with long-travel suspension, for the most part, come with a high-positive offset wheel. This means the wheel center, where it sits flush with the hub, is closer to the outside of the wheel than the center. This puts the center of the tire as close as possible to being right over the ball joint. This geometry delivers the best cornering abilities possible.
This 7-inch-wide HD-9 wheel is labeled as a 6-1 offset. The HD9 we tested is available with or without a beadlock in all black or with a machine/black finish. The wheels start at $157.90.
HOW DO THEY PERFORM?
We mounted the tire/wheel combo on a brand-new Polaris RZR Turbo S. For comparison, we measured the 33-inch Chicane next to the 32-inch ITP Coyote that comes on this RZR. With 17 psi (the pressure we test desert tires at), the Coyote is an exact 32 inches and the STI measured an exact 33 inches. The 1-inch-taller tire gained us a 1/2 inch of extra ground clearance. While we like the traction of the ITP’s Coyote tire that comes stock on the new long-travel RZR, we don’t like the way the tires corner at medium-to-high speeds.
Just by the look of the STI tire, we think it goes great on this larger car. When we got behind the wheel, it was more of the same feeling. On takeoff, the Chicanes grip enough to launch the car forward, but still give it expected wheelspin when you mash the throttle. The acceleration traction felt similar to the grippy Coyotes. When turning, in loamy dirt or sliding on loose gravel, the tire’s best attribute is that it’s totally predictable. The car slides as you would expect and never catches an edge or makes you feel like you are going to high-side or tip over like supper-aggressive tires always do.
For the rocks, we aired them down to 15 psi and crawled over anything—from grippy sandstone to slippery granite with lots of confidence. Even though the tread lugs are not really aggressive, they wrap down the side of the tire some to help grip more than the stockers when driving up against rocks or in deep ruts.
At high speeds, the larger size helps with rocks and square-edge deflection. Bumps that we had normally braced for in standard RZRs, we thumped right over, like rolling over a garden hose. Square-edge bumps, roots or rocks the size of a curb or speed bump were barely noticeable. This tire and wheel combo does weigh 4 pounds more than the stock setup, but you don’t feel the weight while driving, and we didn’t notice any power loss.
For high- or slow-speed driving, it’s hard to beat the predictability of an STI Chicane tire in any size. In our test, we hammered the new meats through the sharpest rock fields, over roots and sharp sticks, and haven’t suffered any punctures after the initial 100-mile test. Tire wear was very minimal. We are going to keep driving the tires in all situations after we mount them on our four-seat RZR Turbo S build this summer. STI HD9 6+1 Comp Lock wheels are available in Matte Black and Matte Black/Machined finishes in 14×7 and 15×7 sizes. All STI tires and wheels are sold by retailers across North America through MTA Distributing (U.S.) and Motovan (Canada). Visit www.stitireandwheel.com.
PRICE: $259.91 (tire); $157.90 (wheel)