Cooper Discoverer AT3 4S Review

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While the Cooper AT3 4S shines in certain areas like wet grip and winter performance, it falls short in others, particularly in off-road durability and handling feedback.

Equinox LT
Discoverer AT3 4S is a great pick for Equinox LT.

Key Takeaway

The Cooper Discoverer AT3 4S excels in:

  • Stable directional grip and braking in dry conditions.
  • Superior wet grip and hydroplaning resistance.
  • Excellent winter performance with 3-Peak Mountain Snowflake certification.
  • Effective sand traction due to lighter weight and softer tread.

It needs improvements in:

  • Steering responsiveness and handling feedback.
  • Durability and puncture resistance, compromising its off-road performance.
  • Ejecting stones on gravelly surfaces.
  • Sidewall’s design, which is not aggressive enough, limiting off-road performance, that comes from reduced air pressure, or flexing sidewalls.

Side Note: The tire has been replaced by Cooper Discoverer Road+Trail AT. Review it here:


The Cooper Discoverer AT3 4S, this tire comes with 42 sizes in total (15″ to 22″ rim sizes) and they have following specs.

  • Load range: SL and XL
  • Speed ratings: T and H
  • Weight range: 31 to 45 lbs
  • Tread depth range: 12.5 to 14/32″
  • All sizes have 3PMSF ratings
  • Warranty: 65k miles

Tread Design

The Cooper AT3 4S distinguishes itself with its exceptional on-road oriented design.

Cooper Discoverer AT3 4S
Cooper Discoverer AT3 4S central 3 block columns have lugs running in pairs.

It features a traditional 5-rib design, with the blocks across all columns, being quite similar in appearance.

I mean all lugs have wave-like siping, and reinforced foundations underneath (as these lugs sit on a secondary rubber layer).

Moreover you also see snow vices, though that’s only common with the outer two ribs, and not the middle one.

Speaking of which, the middle-most rib is relatively wider, compared to neighboring ones.

That’s why the inner 2 circumferential grooves aren’t as wide as the outer.

Moving towards shoulder ribs, the lugs are staggered here, making mud scoops.

And although they make pretty wide lateral gaps in between them, they still don’t loose stability, as these lugs are joined together by ridges, which Cooper calls, Whisper Grooves Technology.

Dry Performance

Overall dry performance is two parts, the tire’s handling abilities, (which checks out its lateral traction, and steering response), and it’s directional grip.

Let’s start with later.

Directional Grip

The tire’s ability to maintain traction while moving in a straight line, is known as directional or longitudinal grip.

This linear traction heavily depends on the tire’s central area (where most of the weight accumulates, while the tire is rolling linearly). And its measured by tire’s braking abilities.

Having said that, the Cooper Discoverer AT3 4S demonstrates appreciable performance here, all thanks to its broad design of its central rib, featuring squared-off lugs.

This design ensures consistent and substantial road contact, optimizing traction.

Moreover, as these lugs are interconnected with each other longitudinally, by ridges, you get superb on-center feel from this tire, adding to its stability.

Moreover, the lateral voids (between lugs), although reduce the rubber’s contact patch, they’re still beneficial, as their zigzag designs allow them to act as biters, adding to the tire’s directional grip, predominately.

As a result, this tire takes the lead among its direct competitors here. To give you an idea, it stops more than 2 feet shorter than its counterpart, the Kumho Road Venture AT52 (review), showcasing its superior dry traction capabilities.

Lateral Grip and Handling

Lateral traction, or the tire’s cornering grip, is significantly influenced by it’s shoulders, (as they engage more actively with the road due to centripetal force, during turns).

Having said that, it can be seen why the Cooper Discoverer AT3 4S stands out in this aspect.

Tire’s symmetric design, featuring compactly placed shoulder lugs with minimal tread features (only lateral oriented siping), maximizes rubber-to-road contact. And that results in this tire getting leading scores in terms of lateral traction, among its direct competitors.

But does that mean, it better in terms of overall handling too? Well not really.

While the tire offers superb lateral grip, it misses out on delivering good enough steering feedback.

This is primarily due to its softer rubber composition, which is winter focused/optimized, making lugs more susceptible to bending and flexing (as the tire corners).

This bending of lugs, leads to a delay that disrupts the tire’s over/under steering balance. And so, the steering feels more sluggish, and less engaging.

But don’t get me wrong, its not too bad, and still manageable, thanks to the tire’s reinforced foundational supports (underneath all lugs), still resitting lugs from flexing way too much.

I mean, compared to the same Kumho AT52, the Cooper’s tire only lacks by less than half of a second, on average, in overall handling lap time tests.

Wet Performance

Wet traction is a crucial aspect of tire performance, hinging on two key elements: wet grip and hydroplaning resistance.

These functions are essential for efficiently evacuating water from the tread, enabling the tire to maintain contact with the road without slipping. So let’s see how our boy performed in each of these.

Wet Grip and Handling

While the majority of water is expelled by the tire’s grooves, residual water particles under the lugs can still pose a risk of slipping.

And this is where sipes come in.

Sipes, small cuts in the tread, play a pivotal role in wet grip, as they absorb the remaining water particles by contracting and expanding, creating a suction effect that helps prevent slipping.

So that means, an ideal tire for effective wet performance needs ample no. of sipes, and flexibility.

And both of these are the traits of Cooper AT3 4s.

The tire offering countless sipes with wave-like pattern provide wet grip (or water clearance), in all directions.

FYI: Wave-like sipes are more efficient, as they are interlocking. So even when the tire takes extreme maneuvers, these sipes remain flexible, and don’t lose water soaking abilities.

Further aiding to these sipes is the tire’s Adaptive Traction Technology.

This features a silica-rich compound that not only adheres well to wet surfaces, but also keeps the sipes flexible and pliant, enhancing their suction efficacy further, resulting in leading wet scores for this tire.

To give you an idea, the tire offers almost 2 seconds faster handling lap time, on averaged tests, compared to General Grabber APT, (review).

Aquaplaning Resistance

Hydro or aquaplaning is a dangerous phenomenon where a tire loses almost all traction by floating on water, due to ineffective water displacement by its grooves.

That’s why tires need powerful and spacious grooves, to disperse water off in time, avoiding tire’s floating, or I should say, hydroplaning.

That’s why the Cooper Discoverer AT3 4S, featuring four circumferential grooves, demonstrates effective resistance to aquaplaning due to its superb water dispersal properties.

Moreover, as these voids are also laterally, connected, it adds to overall water expulsion.

Though the tire could improve its overall float speeds, by removing, what Cooper calls, Whisper Grooves Technology.

These are basically ridges between the shoulder blocks, I talked about it more in the “noise section”.

FYI, float speeds indicate the tire’s limit (or exact point in speed), where it starts to float.

Winter Performance

In evaluating the winter capabilities of an all-terrain tire, three essential aspects have to be considered:

  • Tire’s acceleration.
  • Handling (inclusive of steering responsiveness).
  • Versatility across diverse winter landscapes, especially in soft snow and icy conditions.

And upon examining these aspects, the Cooper Discoverer AT3 4S emerges as a standout choice, leading its category with superior winter performance.

FYI: This assessment is based on rigorous testing and subjective evaluations.

Now, here a significant contributor to its overall “winter scores” is the tire’s superb ice traction, which is especially notable, when you look at the lacking performance on its competitors.

And that is all thanks to the tire’s numerous interlocking biters across its tread.

Here the outer two ribs particularly, make their mark, with lateral notches, and sipes, combined with snow vices (which Cooper calls snow-grooves), a fancy name for the saw-toothed edges, which provide bite on slick surfaces.

Moreover, this bite/grip gets further enhanced by the tire’s winter-tire-like siping, and lugs having chamfered edges, as they promote snow-to-snow contact.

Such contact is vital for overall snow traction, as snowflakes interlock with each other, enhancing friction. These snowflakes don’t stick too well with tread’s rubber.

Moreover, the tire staggered shoulders are also pretty helping in overall snow performance, as they scoop the snow out, backwards generating forward momentum/acceleration against it.

So it makes sense why the tire comes with 3-Peak Mountain Snowflake certification, as this rating is given to tires which perform at least 10% better (in snow acceleration), compared to standard touring AS tires.

Noise Comfort

Tread noise is a critical factor in a tire’s overall comfort, and its largely influenced by the tread design, with shoulder lugs being particularly crucial.

This is because noise gets generated with air particles striking around the tread, as the tire rolls, and that air mostly comes in, through shoulder voids.

That’s why it can be seen why the Discoverer AT3 4S is one of the quietest tires in its category.

It comes with Whisper Grooves technology, where all shoulder lugs have ridges placed in between. This restricts air entry, tackling noise at the source.

Additionally, the tire features a well-structured pitch pattern that reduces in-groove resonance as well.

Though despite all this, there is still some growling noise, and it makes sense, as the tire comes with a ton of siping and biters throughout its tread.

Fuel Economy

The relationship between fuel consumption and rolling resistance is a crucial aspect of tire performance.

This “resistance” is largely influenced by two factors:

  • Tire’s construction weight.
  • Composition of its tread.

Now, although the Cooper AT3 4S has a highly siped structure and a very soft/sticking tread compound (with its Adaptive Traction Technology), its fuel efficiency is still, surprisingly decent.

This is mainly, thanks to its lightweight structure and a well engineered contact patch.

What I mean is the tire is so light that its weight can be compared to less aggressive all season tires. So where its sizes go up to 22 inches (rims), the weight caps at 45 lbs only.

And this is including the LT sizes.

With this light weight, the lugs face less friction, as they get rubbed against the road, enhancing tire’s overall fuel economy.

And yes, with optimized contact patch, the economy is further helped, as each lug has smaller (evenly) distributed weight on it.

Off-Road Performance

Off-road terrains, from rocky trails to muddy paths, test the limits of tire durability and design. Let’s take a closer look at how this tire performed in each of these diverse off-road conditions.

Mud Traction

Mud is a big NO for Discoverer AT3 4S, as it comes with pretty crowded up lug design.

Basically, with all lugs longitudinally aligned, and smaller/narrower lateral voids in between them, the tire doesn’t allow mud to leave out easily, especially in lateral directions, causing tread clogging.

However, a notable advantage is its staggered shoulder design, where lugs primarily assist in scooping and displacing mud backwards, aiding in generating forward motion against the mud.

That’s why those edges on shoulder blocks are often referred to as “mud scoops”.

Sand Performance

Navigating sandy terrains requires not just driving skill but also tires with lower density to enhance performance.

This is because with a lower density, tires are less susceptible to “sink in”, which is another name for “getting stuck”, in the sand world.

Now, in addressing this issue, the Cooper AT3 4S brings several key features to the table:

  • Lighter Weight: A lighter tire exerts less pressure on sandy surfaces, reducing the likelihood of sinking. This is particularly beneficial when climbing sandy dunes.
  • Softer Tread Composition: The softer tread conforms more effectively to the sand (especially with lowered air pressure), enhancing the tire’s grip and contact with the terrain.
  • Staggered Shoulders: These help in scooping and displacing sand backward, thus propelling the vehicle forward.

So you get a pretty efficient tire here. Though there are some limitations too. I mean, the tire doesn’t offer good enough sidewall lugs.

But if sand traction is really important to you, and you need a similar tire, you should check out Cooper AT3 XLT (it’s bigger brother).

Traction on Rocks

The Cooper AT3 4S faces certain challenges in rocky terrains, primarily due to a lack of two essential features: durability and multi-directional grip.

The tire only offers 2 ply polyester casing (in its internal construction), with a mere single cap ply, compromising on its durability a lot.

This makes the tire more susceptible to punctures, even on moderately rocky trails.

Though ironically, this lowered durability also helps in reducing tire’s weight, and that helps with grip on rocks, especially when it comes to climbing (as seen by its effective performance in incline traction tests).

Though this has to do with directional grip, and the tire doesn’t offer good enough results, when it comes to lateral traction.

This lack of sufficient grip can lead to the slipping, particularly risky for sideways slippage that could potentially overturn the vehicle.

Furthermore, the Cooper AT3 4S doesn’t offer significant sidewall lugs. This means that reducing air pressure, doesn’t yield much benefit with this tire.

Moreover, if we talk about gravely roads, (another key area coming in rocky terrains), the tire again lacks, mainly because, its missing with any kind of stone ejectors.

Though the tire does offer chip-protective rubber.


So overall, the Cooper Discoverer AT3 4S is a decent overall pick. The tire offers superb dry performance, in terms of traction, but it needs to improve its steering responsiveness.

Though that’s not the issue when it comes to wet roads, where the tire’s ample siping, biters and Adaptive Technology provide it with leading scores (among its direct competitors).

And yes, same is the case when it comes to winter traction, where its ice grip is the most notable performance attribute.

Comfort-wise, its Whisper Grooves technology minimizes overall noise, (though some growling is still heard).

Speaking of comfort, the tire also offers great on-road smoothness as well, with its softer rubber.

Other than this, the AT3 4S is also appreciable when it comes to fuel economy, and rolling resistance, thanks to its lighter weight.

Though this lighter weight comes at the expense of its compromised durability, which then affects its off-road performance, besides its on-road oriented and less aggressive tread design.

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