The Cooper Discoverer STT Pro and the Toyo Open Country M/T are mud-terrain tires that can be used on the highway, and many people choose them to give their vehicle a more aggressive appearance. However, keep in mind that this bold style may have some downsides.
As a tire engineer, I believe that the Cooper Discoverer STT Pro is one of the best M/T tires for crawling on rocky terrains, thanks to its arbitrary placement of ribs all over the tread. And with its elongated shoulder lugs, and countless stone ejectors, it provides you with a better self cleaning tread. The Toyo M/T on the other side, is better on dry roads, and provides superior fuel economy.
Table of Contents
Tread Design
Let’s start off with Cooper Discoverer STT Pro which is slightly more aggressive.
The tire’s tread consists of just 2 ribs.
The central rib contains 3 unique lugs, with off-set edges, in-groove notches, interlocking sipes, and reinforced foundations.
With this rib, the tire makes a satisfactory directional grip, where the foundational supports add to overall stability.
Though, most of the traction still come from shoulders, as they cover a majority of tread’s real estate.
They from 2 unique blocks there, where one is seen with M shaped siping, and the other one features longitudinal notches/slits in them.
Together they yield wider lateral grooves, forming bold stone ejectors in between.
Moreover, on outer edges, these shoulder lugs are staggered, and create pretty sharp saw-toothed biters on sidewalls.
On the other side, the Toyo M/T produces an average looking “mud-terrain structure”, though it’s having more curves/angles.
With more curves, the shoulder blocks are wrapped by central lugs, and this provides stability on road as well as a strong bite on rougher tracks, (as they interlock with each other).
This also makes a series of circumferential grooves that run along the center of the tire, including wider ones separating shoulder lugs prominently.
These grooves are designed to help channel away water and mud from the tread surface, so they make effective self cleaning properties.
Though all these longitudinal channels are not as wide as the lateral ones between the shoulder lugs, as the tread is the most bald on edges, (where you can also see solid stone ejectors, enhancing cleaning abilities).
Towards the bead/rim area, these shoulder lugs are serrated, forming thick mud scoops (just like the Cooper STT Pro), and they join together there, forming N shaped sidewall lugs for added traction, with lowered air pressure.
Sizes Facts
Toyo Open Country M/T it comes with 83 total sizes in 15 to 26 inches with following specifications:
- Speed ratings: Q.
- Load range of C to F.
- Weight range: 50 to 110 lbs.
- Tread depth range: 17 to 21/32.
The Cooper Discoverer STT Pro on the other side, offers 49 sizes, in 15 to 22 inches and they have following specs:
- Speed Ratings: Q (same).
- Load Ratings: C to F (same).
- Weight Range: 42 to 94 lbs (lighter in comparison).
- Tread Depth Range: 18 to 22/32″ (slightly better).
Internal Build
The durability of a tire depends on the internal build it makes.
And it depends on total no. of plies, though you can’t add too many of these as they are directly proportional to weight, which then harms the tire’s handling capabilities and fuel economy as well.
That’s why some tires like the Cooper Discoverer STT Pro offers just a single cap ply on nylon while Toyo M/T gives you 2.
Though they are both equally durable as they both have 3 ply sidewalls, thanks to their powerful polyester cover inside.
Off Road Traction
Mud-terrain tires are designed to handle a variety of terrain types, including all off road, and not just mud, as their names suggest. Let’s see why.
On Mud
Mud-terrain tires are named that way because mud is the toughest of all terrains. With less aggressive tires although you can still expect a satisfactory performance on rocks, sand gravel, etc, but when it comes to deep mud, no other tire does it better than M/Ts.
And when it comes to these two boys, you cant really pick one over the other, so I am going to rate them both equal.
The Cooper STT pro basically does mud evacuation better, with its wider lateral grooves (and mud prefers to leave off through sideways, especially when a tread is asymmetrical.
But that does not mean it does better, as Toyo M/T provides better scooping of mud trough it’s shoulders and sidewalls, which basically are superior in throwing the mud backwards and yielding forward moving force, as a result.
On Rocks
The Toyo Open Country M/T focuses on lateral traction in a really nice way, with it’s accurate arrangement of notches its able to give you some considerable g forces on sideways.
And it’s “N” shaped sidewall lugs further add to that (mostly seen with lowered air pressure).
Nonetheless as good as it’s lateral component of traction is, it really lacks directionally, and that’s where Cooper STT Pro comes in. The tire brings a well balanced lateral and longitudinal traction, and really does not compromise on one for the sake of other.
That’s why I rated this tire best for rocky terrains in my list of top mud-terrain tires.
On Sand
Sand is not an easy terrain for both drivers and the tires, and here you need a tire which is lighter in weight, and can offer better footprint.
These features basically tell how much the tire “digs”, which is almost the main focus with tire’s traction on sand.
That’s because on sand, digging is your worse enemy. And out of both tires, its seen less on Cooper Discoverer STT Pro.
The tire for one offers a lighter construction where it’s weight only reaches up to 94 lbs (Toyo M/T goes up 110 lbs).
Moreover, the overall average section width (across all sizes) on Cooper is larger, meaning, it gets to offer better footprint on sand, and helping that, it’s it’s elongated lugs and thicker sidewalls, with with lower air pressure provide a sweet footprint for this tire to rock, especially when climbing intense slopes.
The Toyo M/T not only weighs more, but with it’s lower section width on average, it’s can’t keep up as much, as it sides try to dig in (and you don’t really want that on this terrain).
Dry Highway Traction
When analyzing the dry performance of an all-terrain tire, there are three main factors to consider: traction, steering, and cornering ability. Let’s go over each of these in more detail.
Grip
The central area of the tire tread tells a lot about how much directional grip capability is there, as this is where the whole weight gets concentrated on.
And with interlocking structure, as the Toyo Open Country M/T provides you with a more streamlined design of longitudinal lugs and 3 grooves, it’s gets to yield shorter braking distance (a measure of directional grip).
The Cooper STT Pro on the other side, although features a dedicated central rib for the very same purpose, due to wider grooves, it’s still not able to provide as much rubber to road contact, so it lacks slightly.
Handling
The handling of a tire depends on the performance of the shoulders and sidewalls (though there are other factors in play as well, as the tread composition, weight and so on, but the thing is both tires are pretty much the same in all of those).
So with wider lateral gaps between shoulder lugs, the Cooper STT Pro does not provide ample lateral traction here as well, whereas Toyo M/T with it’s angled lugs, with less “randomness” provides a much more smoother exposure with the surface.
Wet Traction
Wet traction is pretty challenging for mud tires, as it has to do with clearing of water, and although with wider grooves both mud tires provide ample hydroplaning resistance, with their abilities to evacuate water out with dedicated channels, they are not able to clean out the left over water, which is actually done with sipes.
Sipes basically offer slits,which literally create a suction by flexing, and slurping water particles in them, and that’s how water gets wipes away.
And so with such limited number of sipes on both tires, they both get to have a limited wet traction.
But still its noteworthy that, the Cooper STT Pro offers better siping structure, whereas the Toyo M/T provides slightly more number of siping.
Fuel Consumption
The fuel usage of a tire is influenced by its rolling resistance, which is then influenced with weight and tread structure.
These factors basically tell with how much force the tread rubs off with the road.
So here with heavier weight and more biters, (on average), the Cooper STT Pro gets to eat more fuel, whereas Toyo M/T with its’ more streamlined design provides better efficacy.
Snow Performance
With both tires just M+S rated, and missing 3PMSF (3 peak mountain snowflake ratings), they are not going to impress on snowy roads, whereas its straight up dangerous to take them on icy roads.
Though they can still work with deeper terrains, as their scooping lugs are very capable.
Nonetheless, they are still better on Cooper Discoverer STT Pro, as this tire produces better lateral tread voids with its elongated lugs.
The Toyo M/T on the other hand, is although good enough as well but longitudinal orientation, it does not offer as much scooping as its competitor.
Takeaway Points
Out of both tires, the Cooper Discoverer STT Pro is taking the lead on rocky terrains as its elongated lugs provide the needed lateral traction, and its countless stone ejectors there keep its tread clear.
The Toyo M/T on the other side is better on dry roads, providing superior directional grip, and surprisingly being a heavier tire, it get to give you better fuel economy in comparison.
