Cooper Discoverer ST Maxx vs AT3 XLT

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Both Cooper Discoverer ST Maxx and the Discoverer AT3 XLT are packed with innovative tread compounds that render epic off-road performance. However, the choice between the two can be difficult. So let me compare the technical specifications and performance data of both to save you some time.

Cooper Discoverer AT3
Cooper Discoverer AT3 is the best combination of on and off-road use.

In my expert opinion as a tire engineer, the Cooper AT3 is a better pick for you, out of both, if you are mostly staying on pavements, as it offers superior, wet, dry, fuel, tread and comfort efficacy. The Cooper ST Maxx, on the other hand, is superior off-road, which is not a surprise, given its rugged design.

Side Note: Make sure you check out my list of top A/T tires, if you haven’t yet.

Tread Design

Starting with Cooper Discoverer AT3, let me divide this in two sections, middle (part of the tread) and the shoulders).

Cooper Discoverer AT3
Cooper Discoverer AT3 is more closed up in comparison.

In the middle:

  • There are 3 longitudinal ribs here, making 4 aqua channels.
  • All blocks in these ribs have full depth wave-like sipes and reinforced foundational supports.
  • The middle most rib is slightly wider, this is done for traction reasons on-road.
  • The outer ribs are made more aggressive as they carry snow vices to them (saw-tooth biters).

On shoulders:

  • Lugs here are elongated.
  • These also have slightly longer sipes on them, though having the same interlocking pattern.
  • The outer margins of the lugs are staggered.
  • Lugs extend down towards the bead area and connect up to form thick enough sidewall lugs.

Note: The sidewall lugs are the main features which differentiates the Cooper AT3 XLT, from the Discoverer LT and the Discoverer 4S, (the other variants of this tire, before it only used to be under just one “Cooper AT3”).

On the other side the Cooper Discoverer ST Maxx features a more aggressive design.

Cooper Discoverer ST Maxx
Cooper Discoverer ST Maxx may be more aggressive, it still missing with good enough sidewall lugs.

Let me divide the tread of this tire in to two sections as well.

In the middle:

  • Lugs are more closed up so on pavements, directional grip is not bad (given it’s a rugged terrain tire).
  • And at the same time they make slanted lateral grooves connecting the outer longitudinal channels, so this way, a grip in all directions is achieved.
  • Moreover, these tread voids also aid a lot in self cleaning, as they are equipped with multiple stone ejectors.

On shoulders:

  • Lugs are bigger here and stud-able.
  • They carry thicker siping pattern as well, and their wider gaps have bold stone ejectors as conventional seen in common on off-road tires.
  • The outer edges of these lugs are although not staggered, you can say each lug is serrated on itself.
  • You also get thicker sidewall lugs too providing ample biter with lowered air pressure values.

Sizes Info

The Cooper Discoverer AT3 XLT here, comes with 32 sizes in total (15″ to 20″ rim sizes) and they have following specs.

  • Speed Ratings: either R or S
  • Load range: C to F
  • Weight range: 44 lbs to 70 lbs
  • Tread depth: either 16.5 or 17/32″ in all sizes
  • Warranty: 60,000 miles

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

Tire’s Toughness

The durability of off-road tires is a crucial consideration, and it depends on the internal construction.

The Cooper Discoverer ST Maxx features a more powerful construction, that’s why as it comes with 3 ply polyester, with third layer at an eight degree bias angle (enhancing strength further), moreover it also features 2 steel belts and a single nylon cap ply on the very top.

Cooper AT3 on the other side although also features a single nylon cap ply layered on 2 steel belts, but it’s 2 ply sidewalls aren’t able to provide comparable durability.

Dry Traction

The dry performance of an all-terrain tire is determined by its traction, steering, and cornering abilities, and it’s crucial to understand each of these key components. Let’s take a closer look at these important elements in more depth.

Longitudinal Grip

Out of both tires, it’s not surprising to see the Cooper Discoverer ST Maxx lacking overall. The tire is much more voided in comparison.

That’s why it shows shorter stopping distances (measure of longitudinal grip), as it’s lateral (wider) tread voids come in the tire’s way to make ample as much contact with the road.

Cooper Discoverer AT3 XLT on the other side, has blocks not only closed up more, they are also aligned longitudinally, so while rolling straight, or highways, you get a better traction and stability.

Lateral Traction

Same thing is seen here (referencing the above section). The Cooper Discoverer ST Maxx with much wider lateral tread voids between the shoulder lugs don’t offer ample handling efficacy.

This is because the tire has a softer compound, more tread depth, weight, and unsupported lugs structure.

All of these cause the blocks to bend and flex more as the tire turns, and this causes under steering at first, followed by over steering, reducing the tire’s overall steering feedback.

Cooper Discoverer AT3 XLT on the other side, has connectors between the lugs keeping them firm with the ground, and so the tire doesn’t limit its steering sensitivity that much, comparatively.

Wet Grip

Although with a much balder structure, the Cooper Discoverer ST Maxx does not have any issues in to channeling the water out in time, it still can’t provide ample wet grip. Let me explain.

With wider grooves, the tire gets to clear most of the water out, but the little that gets left behind has to be dealt with sipes, and this tire doesn’t have enough of those.

Sipes are just slits, which create suction, as they meet the water particles, sucking them in, and “wiping” off water that way.

Cooper Discoverer AT3 XLT on the other side, supplies much better structure, where you see more number of sipes, which also have a better design (they are interlocking, this type of structure is more effective in clearing water).

Fuel & Tread Usage

Both fuel and tread are affected by the tire’s rolling resistance, and structure.

Although both tires have similar weight range (across all sizes), the Cooper Discoverer ST Maxx still puts more pressure over it’s lugs, as the weight gets divided over smaller blocks (surface area).

So they rub off the surface with a greater force, increasing rolling resistance, and hence consuming more fuel.

Cooper Discoverer AT3 XLT on the other side, does the opposite by distribution its weight more evenly, so it’s tread does not rub off the surface with as much force, allowing it to not only have superior fuel economy, but also tread life.

I explained more in:
Do A/T tires wear faster?:

Ride Comfort

A comfortable ride mostly depends on two things, noise and the tire’s stability on roads, and it’s not a surprise to see Cooper Discoverer ST Maxx, with such aggressive hybrid structure, lacking here.

With wider grooves, the tire allows air to easily come in and hit the walls of the tread, producing greater noise, and with greater tread depth, without having any supports, it doesn’t allow for good enough stability.

Cooper Discoverer AT3 XLT on the other side has a more crowded tread, and it’s lugs have reinforced foundations underneath. So air doesn’t have as much area to play around, producing less noise, and its softer compound combined with reinforced foundations provide better efficacy when it comes to overall comfort of the ride.

Grip on Snowy Terrains

All-terrain tires are versatile and can take on a lot on winter terrains, including deep snow, and on-road packed snowy tracks, though they face a hard time on ice.

But on fluffy snow, they are great, as they offer snow grabbing abilities which renders snow to snow contact (better than rubber to snow exposure, which yields less overall friction.

Though out of both tires, the Cooper AT3 (rated with 3 peak mountain snowflake symbol, unlike its counterpart), shows better results.

The tire includes in-groove notches and snow vices on the outer tread voids, which hold on to the snowflakes in a better way.

The Cooper ST Maxx on the other side, is better with deeper terrains, (snow going above 3 feet), and although it’s on-road snow traction is not so great, it’s stud-able lugs allow it to still have a above average gripping capability there, as well.

Overall, being a hybrid tire, its not so bad for winter traction.

Sand Traction

Driving on sand can be a challenge, that’s because besides experienced driving skills you also need a light weight tire capable of spreading out, so you can have ample rubber to sand contact.

And here although it may seem surprising, the Cooper Discoverer ST Maxx is lacking overall due to it’s missing (thick enough) sidewall lugs).

Cooper Discoverer AT3 XLT on the other side, has wider lugs which spread out more with lowered air pressure, and provide better floating abilities with it.

I don’t know why, with aggressive tire like the ST Maxx, you don’t get lugs on sidewalls.

Mud Performance

On mud, the narrower the grooves, the more quickly a tire would get packed with it, and since mud to mud contact loses all traction, it’s a good way of getting stuck on this terrain.

That’s why the Cooper Discoverer ST Maxx with it’s hybrid structure, having mud-terrain-like shoulders yields better results in comparison. As mud easily leave out the tire in time.

Cooper Discoverer AT3 XLT on the other side, has a greater tendency to get packed, though the tire is still not far off here, as its aided by it’s staggered shoulder lugs, and thicker sidewalls, providing paddling on this terrain.

Rock Climbing

A tire that is suitable for rocky terrain must have a soft tread compound that enables the blocks/lugs to bend and flex for improved traction. Moreover, you also need some serous durability, as most of the punctures often take place on this terrain.

That’s why with a more aggressive inner and outer construction, the Cooper Discoverer ST Maxx supplies superior traction here. Its 3 ply polyester sidewalls protect against sharp encounters, and it’s softer compound with wider grooves offer bigger groove mouth to bite in to the rocky surface, generating better grip in comparison.

Cooper Discoverer AT3 XLT on the other side, lacks with it’s packed up structure, and a very squared off, formation of lugs (missing with notches and biters).

Though the tire’s sidewall does provide decent values with lowered air pressure, which reminds me, the ST Maxx could really use more aggressive sidewall lugs.

Are A/T tires good for rocks? :

Leave With This

Cooper Discoverer ST Maxx is a much better tire off-road, considering all, though it’s sand traction can still be improved. As the tire is missing with sidewall lugs, which is odd, given its aggressive structure.

Cooper Discoverer AT3 XLT on the other side, is better on roads overall. It offers superior wet and dry grip, fuel economy and tread life.

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