The Toyo Open Country AT3 and the Cooper Discoverer ST Maxx being powerful all-terrain tires allow you to tackle a lot of different kinds of terrains including smooth highways. Though there are key factors to consider on both. Let’s find them out.
As a tire engineer I can tell you that the Toyo AT3 is better capable of providing you with on-road performance in all departments, may it be traction, comfort, fuel economy and tread life, though it’s wet grip could some work. Cooper ST Maxx, on the other side, is a more gripping tire off-road on all sorts of rugged terrains.
Table of Contents
Tread Structure
The Toyo Open Country AT3 is very well recognized with it’s design. Let me explain.
The tire features prominent S shaped lugs in the middle biters and foundational supports. And making a web of grooves are surrounding lugs which offer similar features though they are positioned at various angles (engineered to provide grip from all directions).
Though that grip is only effective on dry roads, as on wet, they can’t have similar efficacy, despite having numerous sipes.
Moving towards its sides, which are prominently divided by wide longitudinal grooves, the shoulder lugs are very packed here, basically.
That’s because for one, their lateral spacing have ridges in between, and all lugs are pasted on secondary rubber layers. So although you get a great traction on pavements, off-road traction suffers a little bit.
Though a lot of it, is recovered with staggered outer edges and sidewall lugs, which with lowered air pressure provide ample lateral grip on rugged terrains.
On the other side, the Cooper Discoverer ST Maxx also offers you with an symmetric tread design, though its more aggressive.
Where the Toyo AT3 provides you with a combination of vertical and horizontal channels, the Cooper ST Maxx basically supplies better lateral orientation of these grooves.
With this, soft off-road terrains are better dealt with, as thick slimy materials, such as (seen in) mud is easily broken down by the sharp biters/notches, as they escape out away from the middle with help of these tread voids, connecting the outer equally wide circumferential channels.
Furthermore, as these grooves are engraved with multiple stone ejectors, any particles that wants to settle in are kicked out effectively.
And with off-road performance, the closed up lugs also ensure that the directional grip on pavements is also not compromised by a lot, as well.
Though that’s not the case with the shoulders, which although carry similar tread features including snow vices, the wider gaps in between them leave them unsupported and so they lack in lateral traction.
Note that I am talking about pavements here, as off-road you’d have no problem with such aggressive design, and thick sidewall biters.
Sizes Seen
On the other side, the Cooper Discoverer ST Maxx comes in 47 total sizes in 15 to 20 inches. They have following specs:
- Speed ratings: Only Q.
- Load ratings: C to F.
- Weight range: 38 to 70 lbs.
- Tread depth: 18.5/32″ on all.
- No 3PMSF ratings available.
- No treadwear warranty.
The Toyo Open Country AT3 comes in 15 to 22 inches, having following specs.
- Speed ratings: Q, R, S, T and H. (Lean more here).
- Load ratings of C to F. (Learn more here).
- Weight range of 30 lbs to 72 lbs.
- Tread depth ranging from 12.7/32″ to 17/32″.
- 65k miles warranty.
Internal Construction
The harsh demands of off-road driving require the utilization of tires with a high level of mechanical robustness, which mostly includes tough internal construction and thick layer of rubber on top.
And in comparison, it makes sense why Cooper Discoverer ST Maxx is a more durable tire as it features 3 ply polyester, with third layer at an eight degree bias angle, 2 steel belts, and a nylon cap ply.
The Toyo AT3 although also features similar twin steel belts and a single nylon cap ply, it’s sidewalls are protected by just 2 ply polyester carcass, rendering it weaker.
For Your Info: Out of all tires I’ve reviewed, the most durable in A/T category is BFG KO2.
On-Road Capabilities
When evaluating the dry performance of an all-terrain tire, it’s important to consider its traction, steering, and cornering capabilities. Let’s examine each of these crucial factors in more detail.
Dry Grip
Dry grip refers to the tire’s ability to adhere to the road surface while moving straight, that’s why it gets calculated with braking distances.
And in comparison the Toyo AT3 comes out with shorter stopping distance due to it’s more closed up lugs formation. The S and F shaped blocks in the middle are more tightly packed up, in comparison.
Cooper Discoverer ST Maxx on the other side, has more tread voids in between it’s lugs, as it features a hybrid design (combination of mud-terrain and all-terrain features), so naturally its not able to supply you with as much grip.
Lateral Traction
With such wider shoulder voids on Cooper ST Maxx, it makes sense why the tire is not able to provide a good enough lateral traction.
Basically as the tire turns on corners, the whole weight gets directed towards the outer edges, on shoulders and sidewalls, and if they don’t provide ample contact with the road the lateral grip would get compromised.
That’s why Toyo AT3 with such packed up shoulders are able to meet up with the surface of the ground with more consistency.
Tire Communication
The sensitivity of the steering is also a pretty big deal in determining the handling performance of the tire. And here the tread structure plays a major role.
And when it comes to that, the Cooper Discoverer ST Maxx is lacking because of its softer compound, more tread depth and unsupported lugs. All of these cause under and over-steering in the tire as it turns.
This is because with every steering input, the lugs get to bend/flex more with the ground, causing delay.
Toyo Open Country AT3 on the other side, features packed up lugs, and besides having a stiffer composition, it also has reinforcing foundations under all it’s blocks, where the shoulder lugs are further supported with connectors placements in between.
Having such great steering sensitivity and a combination of off-road traction makes this all-terrain tire really worth it.
Wet Performance
Wet traction depends on sipes and hydroplaning. Both of these provide water cleaning abilities.
And although Cooper ST Maxx, provides you with ample resistance to hydroplaning with its wider grooves, channeling water out in all directions, the left over water coming underneath the lugs (directly) is not wiped off efficiently, because of the limited number of sipes.
Whereas on the other hand, the Toyo AT3, providing more number of sipes, grants better wet traction overall.
Fuel Economy
The weight and tread of the tire determine the rolling resistance, which then affects fuel consumption.
In terms of weight, although both tires are very similar, the Cooper Discoverer ST Maxx still gets to consume more fuel, comparatively.
This is because it’s lugs have more tread voids surrounding, and so each lug gets to carry more weight on it, so they create more friction with the road, consuming more fuel.
Toyo Open Country AT3 on the other hand, is not only packed up, but it also has more stable formation of lugs, so they don’t flex as much, which wastes the energy.
Ride Quality
Two primary factors determine the ride quality: tire tread noise, and the tire’s ability to absorb road imperfections through its structure and tread. I’ll elaborate on these.
Tread Noise
The sound we hear (from inside the vehicle), is just the movement of air, mostly coming in through the grooves on the shoulders of the tire’s tread.
This air then collides with tread walls, creating “tread noise”, that’s why Cooper ST Maxx with a balder design gets to be louder in comparison.
Toyo Open Country AT3 on the other side, deals with the noise at the source. With ridges placed between the shoulder grooves, the air gets blocked from coming in. And so there’s no air striking around in the tread causing noise pollution.
Comfort
A tire’s comfort level is linked to its capacity to absorb road shocks, which is primarily influenced by its composition.
That’s why Cooper ST Maxx with a soft-treaded compound provides you with a more comfortable ride by effectively reducing vibrations.
Furthermore, the increased tread depth of the tire (on average) provides a greater cushioning against road roughness, thanks to the thicker rubber layers between you and the road.
Toyo Open Country AT3 on the other side, provides you with a slightly more jittery ride, both on and off road.
Winter Traction
Out of both tires, it makes sense why Toyo AT3 is only one with 3 peak mountain snowflake and M+S rating, which basically tells that the tire is 10% better at directional grip compared to average all season tires.
This is because this tire features smaller notches and effective siping all over the tread, and these are better able to grip on to the hard packed snow.
The Cooper ST Maxx on the other side, only does better with off-road snow, where it’s wider grooves, and snow biter on the outer longitudinal grooves come in to action.
For Your Info: Mickey Thompson A/T provides the best grip on snow in all-terrain category.
Off Road Traction
The difficulties of off-road terrains can vary, with mud being particularly demanding and requiring specialized tires, while gravel and dirt roads can be easily navigated. That’s why I’ve chosen to go over each terrain separately.
Rocky Areas
Out of both tires, The Cooper ST Maxx gets to provide better rocky terrain traction, and it’s not surprising given it’s aggressive design.
In the middle of its tread, you get bigger groove mouth, biting in to the rocky surface with a greater force, and with haphazard placement of blocks, with notches and off-set edges, you get additional bite in almost all angles.
Moreover, you also get very aggressive shoulder lugs in comparison, on this tire as well. Each of its block is staggered on itself, and have sharper edges towards the middle granting it with additional grip.
Toyo AT3 on the other hand, isn’t able to offer as much sidewall and shoulder biting, comparatively, though it’s middle part still grants decent grabbing abilities.
Recommended Read –
Are A/T tires good for rocks? : https://tiredriver.com/are-all-terrain-tires-good-for-rocky-terrains/
Lighter Mud
To perform well in mud, all-terrain tires require a tire with self-cleaning abilities and a more robust tread pattern. This will help to remove mud quickly and maintain traction.
And this is the reason why out of both tires, you get to see a better performance on Cooper Discoverer ST Maxx. The tire provides you with a balder design and its shoulder lugs are equipped with bold stone ejectors, keeping the tread clean.
Toyo Open Country AT3 on the other side, does not make as wider of the grooves, and it’s packed shoulder voids and missing stone ejectors causes it to pack much more quickly, in comparison.
Soft Sand
On sand you need a wider footprint, so the tire can float better. And out of the two, the Cooper ST Max is better at providing that.
It’s section width on average is greater in comparison (considering all sizes), and with the thicker sidewall lugs you get to have more contact patch with the sand as those lugs spread out with lowered air pressure (which you always do).
Toyo Open Country AT3 on the other side, is a harder compound for one, and with sharper sides and thinner sidewall lugs, its more difficult to escape it from digging, especially during climbing on sandy dunes.
Tread Life
Tread longevity is a result of the interplay between rolling resistance, tread depth, and composition. That’s why tires with greater tread depth and a stiff composition will experience slower wear.
And so with lower rolling resistance on Toyo AT3, and a stiffer compound, it makes sense why the tire has tread wear warranty up to 65k miles, whereas you don’t see any coming with it’s competitor.
The tire basically has closed up tread blocks and a stiffer built with ample tread depth. The closed up lugs distribute the weight more evenly, so they don’t rub off the road with too much force. And the stiffer composition don’t cause too much “burning” to begin with.
Moreover, with tread depth reaching up to 17/32″, the tire takes a long time before reaching to 2/32″ legal limit.
Cooper Discoverer on the other side although also features tread depth up to 18.5/32″, the softer compound and heavier weight, still causes faster wear in comparison.
To Sum Up
So overall, although Cooper ST Maxx provides you with a decent on-road grip on dry (especially directional), with such wider grooves it’s still not enough compared to its counterpart.
And that goes especially for wet traction, though its not good on both tires.
Toyo AT3 on the other side, performs better in nearly all on-road metrics, and lacks off-road comparatively.
