Sumitomo Encounter A/T vs Cooper Discoverer A/T3

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Sumitomo Encounter A/T and Cooper Discoverer A/T3 are on-road oriented all-terrain tires. These babies are built for light trucks and full-sized SUVs, but don’t let their smooth design fool you as they can handle some serious mild off-road tracks with ease, thanks to their beefy sidewalls and deep biters. But looking at these two, it begs a question, could we have a new off-road champion in town?

Cooper Discoverer A/T3 XLT
Cooper Discoverer A/T3 XLT variant is the only one with good enough sidewall lugs.

Being a tire engineer, from my perspective, the Japanese Sumitomo Encounter A/T offers a pretty noticeable on-road performance, where its both wet and dry traction is almost like any other passenger tire. So it offers a cozier ride. Due to it’s stiffer sides, it offers better on-road stability. The Cooper A/T3 also offers decent experience on smooth tracks, but it’s off-road traction is a little superior, yet both do equally good on (light) mud.

(Highlighted links above contain their detailed review, it’s recommended you check them out first, for better understanding).

Sizes Info

Starting with Cooper AT3, this tire comes in 15 to 20 inches with following specs.

  • Speed ratings: R and S.
  • Load range: C to F.
  • Weight range: 44 lbs to 70 lbs.
  • Tread depth: Either 16.5 or 17/32″ on all sizes.
  • Warranty: 60k miles.
  • Winter Ratings: 3PMSF and M+S.

Sumitomo Encounter A/T, in comparison, also comes in 15 to 20 inches but with following specs.

  • Speed rating are available in Q, R, S and T.
  • Load Ratings: SL, XL, C, D, and E.
  • Weight varies form 34 to 84 lbs.
  • Tread depth range: 13 to 20/32″.
  • Warranty: 60k for all sizes.
  • Winter Ratings: 3PMSF and M+S.

So, looking at both, it can be seen that Sumitomo is a heavier tire due to it’s larger tread depth going up to 20/32″. Moreover, the tire also offers similar tread wear warranty in comparison, but have superior speed ratings.

Tread Design

The Cooper A/T3 XLT boasts some seriously impressive sidewalls, with lugs that are thicker and more durable than those found on other versions of the tire (namely, AT3 4S and the AT3 LT).

Cooper Discoverer AT3 XLT
The staggered shoulders of Cooper Discoverer A/T3 XLT join together on sidewalls.

Out of both tires, this one basically offers thicker lugs, and with lowered pressure, they are able to enhance the tire’s overall foot print.

These lugs basically join the staggered shoulders, so its sides are more aggressive, comparatively.

In the middle you get to have 3 main ribs, where blocks run in pairs (interconnected with each other from underneath with tie bars).

And although, they carry full depth interlocking sipes, you don’t see any biting notches on them.

But on the outer circumferential channels, the tread makes a more aggressive pattern, as its equipped with saw tooth edges from both sides.

Basically the blocks surrounding have that, and I believe the technical term for that is “snow vices”.

Also worth reminding, the tire gets to have wider central-most rib in comparison, which basically provides superior directional stability.

On the other side, we have Encounter A/T from Sumitomo which also offers a 5 rib design, 3 ribs in the center and wide shoulder lugs on the sides.

Sumitomo Encounter A/T
Sumitomo Encounter A/T features M shaped sidewall lugs.

Starting form it’s sides, it’s sidewall lugs are although not that thick, they still cover more surface area of the bead.

The outer edges of the shoulder are not properly staggered, and make smaller mud scoops, though you can say each lug has a staggered design of its own.

These shoulder lugs are pretty big, compared to the ones in the middle, and their elongated design have thick wave-like full depth siping on them.

They are separated form the middle part of the tread by zigzag wide circumferential grooves.

The middle area of the tread contains even smaller ribs in the very middle surrounding by T shaped (if you will) lugs on sides.

They carry slightly different siping pattern, though it’s still somewhat interlocking, and also full depth.

Yet, both these are pretty effective, I mean it’s dual siping design puts its wet traction off the charts, outperforming some of the major key players in the market.


The durability of an all-terrain tire is largely determined by its internal construction, specifically the construction of the sidewalls.

And both tires are equal here, well on the paper, where they both have 2 ply polyester casing, with 2 steel belts and a spirally wound nylon cap ply.

Though in real life, the Cooper AT3 provides slightly better durability, with it’s superior cut resistant rubber, and thicker sidewall lugs, protecting the most vulnerable area of the tire.

Dry Performance

To assess the dry performance of any all-terrain tire, we need to consider traction, steering, and cornering ability. Let’s look at each of these factors individually.

Dry Grip

Although other factors, such as the tire’s composition and rolling resistance, may also affect grip, it’s still largely determined by the central area of the tread, which should have as much contact with the road as possible, for optimal grip.

So balder the tire, the more the grip gets compromised.

And although, comparing both tires, there is only a negligible difference in the footprint offering, the Cooper Discoverer AT3 is still able to pull off better performance values.

This tire basically provides thicker ribs in the middle, meaning it’s central most lugs (which make the strongest bond with the road), have more width, which translates in to better friction, and hence grip.

The Sumitomo Encounter A/T on the other side, if you consider it’s tread again (by scrolling above), you’d note that it’s circumferential grooves pack up the central rib and it’s not as wider in comparison.

Though, it does good at higher speeds, where it speed rating is also slightly better, available up to R, whereas Cooper AT3 provides up to S (that’s a difference of 6 mph).

Dry Handling

Lateral traction, or the tire’s ability to corner, is largely determined by the shoulder lugs and their tread structure and yes, composition too.

Basically, the shoulders bear the “majority” of the vehicle’s weight, during turns and need to have a strong bond with the road to maintain traction.

The Sumitomo Encounter A/T is better here as it promotes more uniformity on it’s shoulder lugs.

These lugs are also bigger compared to central ones, and with that, they allow a better rubber to road contact enhancing lateral traction.

The Cooper AT3 is off ( but with a very small margin), it’s shoulder lugs are smaller in comparison, even though it’s packed up with stronger ridges in between (providing whisper groove technology).

Steering Response

Tire responsiveness is a measure of how well a tire communicates back to the steering inputs, and can be influenced by factors, such as weight and sidewall design, which can affect the continuity of contact between the tire and the road.

The Sumitomo Encounter A/T is slightly heavier in comparison, and it’s tread depth is also greater on average, so it tends to understeer more compared to Cooper AT3, as the energy is used up in to flexing its lugs.

Wet Traction

On wet roads, it’s important for a tire to have both good grip and hydroplaning resistance in order to quickly clear water from the surface. I’ve discussed both below.

Wet Grip

The wet grip of a tire is largely determined by its siping, which helps to absorb water and improve traction. It’s important for the sipes to be flexible in order to allow for efficient water cleaning.

Out of these both, the Encounter A/T is one of the top performing all-terrain tires.

To give you a rough preservative, it’s wet traction is on par (if not greater) compared to Falken Wildpeak AT3w, and that tire is pretty epic on wet (you can find its review as well, or compare it with others).

Sumitomo A/T basically offers dual siping pattern, where both the middle and shoulder lugs contain interlocking design, which stays flexible in all conditions, allowing superior water wiping abilities.

The Cooper Discoverer AT3 is also pretty great, but it’s sipes are outnumbered here, so comparatively it lacks a little on both wet braking distances and handling times.


The risk of hydroplaning increases at higher speeds, so a good resistance to that allows tires to be more stable on highways.

Basically, it occurs when a layer of water comes in between the tread and the road, and tire starts to float. To prevent this, treads are build with grooves, so water can leave out as soon as possible.

So with better hydroplaning resistance, it can be explained further, why Encounter A/T offers better overall wet traction.

This tire basically allows better channels (both lateral and longitudinal), whereas Cooper AT3 only allows water to move out vertically (for the most part).

So with more water evacuation, there’s less for sipes to sit on, and this improves the overall efficacy for the Sumitomo’s boy.

Fuel Consumption

Fuel usage is directly related with rolling resistance, which is calculated with the greater frictional forces with the road.

Out of both, the Cooper Discoverer AT3 provides better efficacy here, as it’s the lighter one in comparison.

With just a single cap ply, (and 2 ply sides), it offers much less pressure on it’s lugs.

To be more specific, it’s weight is distributed evenly on a larger closed up area of rubber, so all lugs get to rub (with the road) with less force.

Sumitomo Encounter A/T on the other side, is although pretty streamlined for directional grip, it’s heavier weight, and softer compound, both causes to have higher rolling resistance, and hence it consumes more fuel as a result.

Tread Life

The wearing of the tread is also related to rolling resistance, though with more stretchability, and larger tread depth, tires are made to last longer.

That’s why Sumitomo Encounter A/T with tread depth reaching up to 20/32″, still takes almost similar times to wear off compared to Cooper AT3, though it’s rolling resistance is much greater.

That’s why these tires are also very similar in terms of their mileage warranty. They both provide you with 60k miles.

Winter Traction

All-terrain tires are getting better at providing all season traction, that’s why almost all of them coming in have 3 peak mountain snowflake ratings. And these two are in that list as well.

Both of these tires actually have a lot of winter tires’ features, like their rubber is plum, and they have notches which act as snow trappers.

But still out of these, Cooper AT3 is taking the larger piece of the pie. The tire basically has snow vices all over it’s outer longitudinal grooves.

They are actually on blocks facing from each sides, and these saw tooth edges provide efficient snow grabbing abilities.

Moreover, the tire siping is also better optimized for snow and on top of that, it’s section width is also narrower. Both of these promote snow biting.

Sumitomo Encounter A/T on the other side, is not too far off, and is pretty great with light snow-filled-roads.

It’s softer tread compound is actually the one most considerable here, because its very thermal adaptive, so with freezing temperatures, it does not become a brick, and keeps it’s biters flexible.

Comfort and Noise

Both noise/comfort are basically on road factors, and both are dependent on overall construction of the tire.

If I talk about noise first, you have to understand that it’s just the air moving in and out of the grooves, and as most of it enters/escapes through the lateral gaps of shoulders, the Cooper Discoverer AT3 offers ridges there (blocking the gaps, basically).

So with that, very restricted amount of air is able to get in, and hit around to create noise. Cooper calls it whisper grooves, and provides a better (quieter) ride in comparison.

On the other side, the Sumitomo Encounter A/T is although not packed up with ridges on sides, it’s still not bad as it offers a better pitch sequencing, some also call it “variable pitch generating tread”.

With this air hitting different parts of the tread create different frequencies and cancel out each other to minimize the noise.

But still I am going to give an upper hand to Cooper Discoverer AT3 in this section.

Sumitomo Encounter A/T on the other side, is better at absorbing bumps, as it’s softer rubber is quite thick, going up to 20/32″ in tread depth.

Traction Off-Road

When driving on rougher terrains (like mentioned below), there are several factors that can impact performance values.

So considering all, lets see where these tires stand.

On Mud

On mud you need scooping and faster debris evacuation, both are achieved with balder tires unlike these two we are discussing.

Though still out of them, Cooper AT3 does better, with its’ slightly more open tread voids, and bigger traction scoops (forming chunkier sidewall lugs).

With that mud gets to leave out faster, while the sidewall/shoulder provide the necessary digging/scooping.

Sumitomo Encounter A/T lacks in all these areas. It’s M shaped sidewall lugs, aren’t great at digging, and there aren’t any staggered shoulder lugs featuring mud scoops on sides.

Gravel and Dirt

It’s pretty common for stones/dirt to get lodged in the tread of the tires, on gravely roads. But to avoid that there are designated stone ejectors, so those can be removed before they dig in to the tread (causing damage).

Although both tires here, have chip-resistant treads to protect against that damage, the missing stone ejectors in Sumitomo Encounter AT reduces the tire’s overall capability.

On the other side, the Cooper AT3 offers stone ledges which keep a majority of these unwanted stones out.

And helping to that, are ridges in between shoulder lugs, they also act as dirt ejectors further cleaning the tread.

Rocky Terrains

On rocks, you need to have large enough grooves, so they can bite in, and you need a lot of notches to grip in all directions along with durability.

Although all of these features are lacking in both tires, the Cooper AT3 still does a better job with it’s efficient sides, providing greater lateral traction (highly needed on rock climbing).

With staggered shoulder lugs, and thicker sidewall design, it basically offers a lot more footprint with lowered air pressure.

So although there aren’t efficient biters in the middle, they still provide slightly better results in comparison.

On Sand

Out of both tires, the Cooper Discoverer AT3 does a better job on this soft terrain. That’ because it average weight is almost 10 pounds lighter and it’s sides/shoulders are not too sharp.

Both these things actually contribute to tire’s forward momentum, and that’s exactly what you want on sand.

The Sumitomo Encounter AT, conversely, with heavier weight (reaching up to 84 lbs in weight), gets to be more digging in comparison, which makes it more susceptible to getting stuck especially on slopes.


Both tires are very on-road aligned with their 5 rib structure, with a slightly more open design, the Cooper AT3 does better on rugged terrains, where it can evacuate out dirt and mud faster.

It’s sidewall lugs, moreover, also allows it to have superior lateral traction on rocks.

On roads, it does better with noise, and dry grip, but here overall performance is more noticeable on Sumitomo A/T.

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