By Cody Hooper
STI’s new Enduro DOT rated radial tire offers serious performance and great life
We are about to crest the point where a standard UTV tire shares more of its build structure with light truck tires than their ATV counterparts. It’s a good thing, too, because we have been left wanting for more strength and puncture resistance than a standard OEM tire will give you for years. Tires and wheels are one of the top-selling aftermarket products in the UTV segment, and have been since the invention of the UTV. It’s not hard to see why- tires are a wear item for one, and large performance increases are readily attainable by outfitting your UTV with the right meats for your riding conditions and terrain.
For this test, we mounted up a set of STI’s new Enduro XT/S tires on a set of their HD9 Comp Lock wheels. The HD9 is STI’s strongest beadlock wheel, utilizing an 8-spoke design in multiple finish options, including black, bronze, and machined with color-option beadlock rings. The HD9 wheel uses a 10mm thick beadlock ring secured by large 5/16-inch grade 8 hardware. This is the same wheel that STI’s sponsored Baja race teams ran last year, meaning the wheels are tough enough to finish one of the harshest offroad races on the planet. They include pre-installed valve stems that are sleeved for protection from rocks and debris. They are available in 14×7 and 15×7 sizes, with 4/110, 4/156, and 4/137 bolt patterns. Online pricing puts them between $108.95 and $139.99 each.
The Enduro XT/S tire is STI’s first venture into a light truck-style tire, with a flat center section and rounded side lugs for smooth use on and off road. The tires roll smoothly on hardpack, eliminating the tire thump and hum you get from offroad-style tires with large lug spacing and tall tread blocks. The dual steel-belted radial tire is constructed from 8 plies, giving it incredible strength and predictable performance through load and pressure changes. It is available in four sizes: 28/9.5R-14, 30/9.5R-14, 30/9.5R-15, and 32/10R-14. Weight ranges from 39 pounds for the 28 inch to 46.3 pounds for the 32, with load ratings from 760 lbs/tire to 1020 lbs/tire, respectively. They can be found at most local or online retailers, starting around $140/tire.
We mounted the STI wheel and tire combo on our resident 2017 RZR XP4 Turbo built by TMW Offroad, a stripped-down, light-weight 2 seat conversion build with Walker Evans Racing Velocity Series shocks and some engine work by Weller Racing (see TMW SCARAB XP4 TURBO). This car is FAST, so we needed a robust tire that could keep up with the speeds and side loads we threw at it. Our testing started in the Mojave desert, and stretched up to around 8,000 feet of mountain elevation featuring some of the most brutal, unforgiving rocky hill climbs we could find. Our testing took place over 3 trips totaling just shy of 200 miles.
Initially, the appearance of the tire is deceiving, as the flat profile tricks your eye into thinking the tire is smaller than it is. It measured just over 30 inches tall at 15 psi on our RZR. Low-speed turning is very smooth, and the tires track very well even with the long chassis of our XP4. Rolling on hardpack or asphalt, the tires are incredibly quiet and refined, causing no shaking or vibration. Where this tire really starts to shine, however, is when the speed picks up.
With such a strong carcass, there is seemingly zero perceptible tire wobble or deflection when you hit a square-edged obstacle on the trail. Typically with tires 30 inches tall and larger, there is a perceptible wiggle in the steering wheel when you smack a rock or a big hole on the trail at speed as the tire’s carcass flexes and shakes. The absence of that feeling with the Enduro tire builds confidence with every mile behind the wheel. The tires grip incredibly well on hardpack and loose, dusty soil, allowing you to place the car very well without worry of losing sidebite unpredictably. Forward traction in 2WD was decent during our testing, but was hampered by our Turbo RZR’s aggressive clutching and big horsepower numbers. Put in in 4WD, however, and the car hooks up and takes off like a rabid dog. Initial cornering feel is tidy and controllable, giving the car a much more balanced feeling than it had on the stock, staggered-size Bighorns. Turn-in precision is great.
In our rocky hill climb and gravel test sections, the combination of the STI Enduro tires and the excellently-tuned Walker Evans shocks allowed us to pretty much hold the car wide open and steer around obstacles with zero drama. Even smacking a football-sized rock with a front tire goes over without drama. It’s a nice feeling being able to drive the car over obstacles rather than try your hardest to avoid them, and they are no worse for wear after our brutal beating during our test loops. In fact, the tread wear is absolutely incredible for the amount of rock we have spun them over at speed. We can easily see these tires lasting 1000-1500 miles under hard use, and much longer during normal driving.
In wet, loamy soil, the tires bite so well, we actually preferred driving the car in 2WD. At moderate throttle openings, the Enduros tracked very well without excess wheel spin. If we have one complaint, it’s the tire’s weight. However, knowing that it’s a dual steel-belted radial, the weight is completely understandable. With that in mind, we noticed no detectable loss in power or increase in steering effort using the Enduro XT/S tires. We would trade the strength for the weight any day, and they are actually a bit lighter than some 28” tall 8-ply tires we recently tested (that will remain unnamed here). They give a huge confidence boost concerning durability, and taking off for a long 100+ mile ride is more enjoyable knowing you don’t have to identify and miss every single obstacle that could cause a puncture with a weaker tire. Just remember, no tire is bulletproof.
Overall, we are thoroughly impressed with STI’s Enduro XT/S tire. It provides great cornering traction, good acceleration and braking traction, and awesome durability. It’s a well-rounded option for a variety of terrain, and the carcass is still flexible enough to run at 15 PSI without rattling your teeth out over small, high-frequency impacts like rocks or washboard. At lower pressures, the grip gets even better, but we found ourselves sticking at 15 PSI to keep the sidewall flex to a minimum. Grip is the name of the game here, and the STI Enduro XT/S delivers in spades.
CONTACT: STI POWERSPORTS, www.STIPowersports.com