While we're usually interested in tires that range in size from 35-44" in diameter, sometimes we need smaller sizes for our daily drivers, too. When it came time to replace the OE tires on our '07 GMC Yukon XL, we turned to Toyo. Our past experiences with the Toyo Open Country MT and AT tires are that they're reliable, true, and competent on both the pavement and in the dirt. We'd never run the smaller version of these tires, so were curious to see if they're as good as their larger siblings.
Since the Yukon is our family truckster, it sees everything from grocery getting to mild backcountry dirt roading. It also sees plenty of snow, ice, and road salt in the winter. We were especially anxious to procure a tire that works well in the snow. We weren't adding a suspension or lift to our Yukon, so went with four 265/70R17 Open Country AT tires that are the same size as the OE tires (about 31.5" diameter). The Toyos utilize DSOC II technology. Here's what Toyo says about that:"Dynamic Stability Optimized Contact (DSOC) theory technology was first utilized in 1988. Toyo introduced an updated version of this technology, called DSOC II, in 1995. The latest "T mode" technology is based on DSOC II, but is even more precise and evolutionary.
The Toyo Open Country AT tires...
The Toyo Open Country AT tires balanced perfectly and had very little radial runout.
"T mode" captures every movement of the vehicle in order to analyze its data and then combine it with tire behavior analysis. It has enabled us to create more accurate and ideal couplings, which designates which type of tires fits best on particular vehicles. It is the result of carefully integrating driving simulation and tire simulation. "T mode" is truly an amazing technology that will revolutionize the tire industry in the 21st century.
Analysis software for "T mode" integrates one driving simulation and three tire simulation software modules. The driving simulation software, called ADAMS, incorporates parameters such as high-speed straight driving, lane-change, emergency avoidance, slalom, and braking performance simulations. The three tire simulation software modules are STACS II, CASPAN, and MSC. They incorporate performance data such as contact-surface, cornering-force, hydroplaning, vibration analysis, and rolling resistance simulation.
"T mode" combines all of this analysis data. This new technology enables us to evaluate tire-loads correctly, optimize tire-structure, tire-material and design tires that can be perfectly matched with a vehicle."
 It's always a pain to deal...  It's always a pain to deal with the Tire Pressure Monitoring System (TPMS) on newer vehicles. |  The Toyo's tread design is...  The Toyo's tread design is computer designed for quiet operation and good traction. The open shoulders let water escape so the tires resist hydroplaning. Note how many sipes are in the tread blocks. These tires should work very well in the winter. |  The Open Country ATs look...  The Open Country ATs look great on our Yukon XL and are an improvement over the OE tires they replaced. |
That techno-speak translates into this tire is designed well. We can tell you that the Open Country ATs are mud and snow rated all-terrains with two wide steel belts, open shoulder design, high turn-up polyester construction, spiral-wound cap ply, special wavy sipe arrangement, and a single-strand bead wire package. The wavy sipe arrangement is interesting to those of us who use our tires in snow country. The Open Country ATs are heavily siped and should work well in the white stuff.The Toyos are true to their legacy and took almost no weight to balance and had very little radial runout. This translates to a smooth, vibration- and wobble-free ride on the blacktop. We tried them on a dirt road and found traction to be much improved over the OE tires, with lateral grip being especially good, both on- and off-road. The tires are also quiet. We have no snow yet, so can't report on their snow performance, but will keep you updated.
On the little slickrock we drove over, the Toyos gripped much better than the OE tires did. We don't expect mud performance to be very good, but these tires aren't mud tires, are they?
We'll keep you updated on how the Open Country ATs perform. Other owners report good wear characteristics and our tires came with a 50,000-mile limited tread wear warranty, so we imagine we'll get some mileage out of these. Usually in our world, the better a tire wears the less they grip in the rocks. The Toyo Open Country ATs may be the exception to the rule. It looks like the smaller Toyo Open Country AT tires are as good as their larger siblings and continue Toyo's tradition of quality tires that really work.