Cooper Discoverer STT Pro Review

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Cooper Discoverer STT Pro serves you off road in a much better way, being an aggressive mud terrain tire. It’s combative lugs with deep biters supply maximum rugged terrain capabilities. And its wide range of sizes allows it to be used on all types of trucks and heavy duty SUVs.

Cooper Discoverer STT Pro
Cooper Discoverer STT Pro upper sidewall design enhances traction

Being a tire engineer, in my opinion, the Cooper Discoverer STT Pro offers a very great computer optimized tread design where it’s lugs vary in shapes vigorously. These provide ample biting off road, making this tire one of the best mud terrain tires that you can get for rocky terrains. Moreover, with all season compound the tire is also pretty great on both wet and dry conditions, and compromises very little on smooth pavements. But it may bother you with it’s tread noise little bit, but I bet you’d get used to it in no time. Also it’s also very impressive in the tread wear area and lasts quite a while, but is a little loud but you soon get used to it. Also one more thing, with this tire, be ready to visit fuel pumps everyday.

FYI, although looks are subjective, in my opinion, it’s the best looking tire in the mud terrain category.

What you think?

Tread Looks

Cooper Discoverer STT Pro is a very aggressive looking mud tire.

Cooper Discoverer STT Pro
Cooper Discoverer STT Pro

It central area consist of 3 unique ribs which have interlocking full depth siping on them. This pattern of siping is seen on a very few Mud terrains, and they provide better efficacy over regular ones.

Other than sipes, all three of these ribs make interconnected grooves meeting with the outer wider lateral channels along the shoulders.

Also note how all of it’s lugs have reinforced foundations underneath which allows it too have highway stability (for the most part).

Moving on to the shoulders, the tire offers 2 unique lugs here, where one has similar wavelike siping and the other is made more aggressive where there are slanted longitudinal groove notches seen.

Between these blocks very bold stone ejectors run. In fact these are the most bold ones I’ve ever seen on any tire (in this category).

Sizes Guide

The Cooper Discoverer STT Pro comes in 49 total sizes ranging from 15 and going up to 22 inches (rim sizes).

All of the sizes are equipped with speed rating of Q, which is the average when it comes to mud tires, meaning haven’t seen any rugged mud tire capable of providing more than Q.

Learn more about speed ratings:

Talking about load ratings, that’s also average, as it provides ratings ranging from C and going all the way up to F, and with which the tire’s weight also changes by a lot of margin.

The lightest tire is seen with 42 lbs while the heaviest is 94 pounds (still overall, the construction isn’t that heavy I’d say).

All sizes get to have tread depth staying between 18 and 22/32″ (including them), where you are going to see most of the sizes with 21/32″ (which is nice to have, as it directly affects the tread wear, so the more the better).

Also note that none of the sizes are branded with 3 Peak Mountain Snowflake rating though they still carry M+S.

And yes there’s no tread wear warranty on any size either.

For Your Info: Best all rounder MT tire is BF Goodrich KM3 (review).

Comfort and Noise

On highways, noise is created with a plenty of characteristics of the tire, where some noise generates by tires rolling, some by air hitting the grooves, some with tread’s composition where softer rubber resonates more, the list is big.

But the main focus is one. Make tire quieter.

Now when it comes to Cooper Discoverer STT Pro, although provides pitch sequencing, which tires to dampen the noise.

The baldness of the tire offers a huge room for air to move around and hit the grooves, creating groove resonance and produce loud tread noise.

For Your Info: Pitch sequencing is often refereed to as variable pitch technology and with this all tread blocks are made with slightly different shapes, so this way air hitting those create different tones and frequencies, which try to cancel out each other.

But it’s not not enough here as STT Pro is aggressively voided.

By the way, the quietest tire in the mud terrain category is Falken Wildpeak M/T (review).


Cooper Discoverer STT Pro features a Armor-Tek3 technology where it’s inner construction is made out of 3 ply polyester cover with high turn up.

This cover is then strengthened with two wide steel belts (covering the central tread area from underneath).

And these belts are then reinforced with a single cap ply of nylon.

For Your Info: It’s belts are pretty solid, you can literally stand on a sharp nail on this tire and it would not puncture it’s tread.

Mostly the mud tires get to have 2 ply nylon, but with a single ply , although durability is compromised a little bit, its a nice balance between being light in weight (which helps with highway factors) and durability where the weakest are the sidewalls, and they are protected by 3 ply polyester with high turn up carcass.

In additional to that, the tread of STT Pro is cut resistant as well, so this further strengthens the overall structure.

Street Performance

When it comes to mud terrain tires, pavement grip is not usually their strongest suit, as these tires aren’t capable of providing enough feedback to steering , grip, as well as lateral traction while cornering.

These are the main factors which tells you about the overall performance of a tire, so let’s analyses them one after another.

Tire’s Feedback

You can’t expect a mud tire to be as vocal as an AT or even RT tire (hybrid). The limited feedback of mud tires is simply created when it makes a larger gap between over and under-steering

And Cooper Discoverer STT Pro is no exception here, it’s chunkier lugs although offer a good lateral forces, the asymmetric design of it’s tread does not offer the needed stability.

Here the tire’s stiff sides and the weight act as a catalyst, and so when you turn the tire, there is a delay between you steering right or left and the tire turning.

This is enhanced or you can say visualized when you take faster turns. In this scenario the Cooper STT Pro would feel resistant to turning at first, and then later it would try to go over.

Traction on dry roads

Traction is not the grip, it’s just a part of it, the other piece of the pie, or should I say a larger piece, is dependent on the tire’s lateral stability and forces exhibited.

The STT Pro although offers a nice directional stability. Scroll above and check out its tread one more time, look for how the tire makes horizontal wave like pattern with all it’s lugs.

All these together provide a scooping effect on the ground, and although it’s great for loose surface, on harder it’s very bumpy, though you can achieve slightly better gripping values by lowering the pressure, (but also note that it would also make this tire consume more fuel, which is already not super great).

Wet Performance

The performance of a tire on rainy season is going to be dependent on hydroplaning as well as the grip.

Both are very important key components, though there are other factors as well.

Let’s discuss how these affect the tire’s overall performance.

Wet Traction

The stiffer the composition gets, the limited the wet traction gets, and that’s bad news for the Cooper STT Pro as the tire does not offer a flexible rubber top.

Another key component here, the overall siping, is also very limited here as well, as these slits actually provide efficacy by sucking water in them.

There are very few sipes overall, and even those don’t offer better expansion and contacting to soak up the water away.


Hydroplaning is when a tire can not grip on standing water, so here a tire needs to clear it off quickly, so it would not float.

But usually, hydroplaning is not an issue with highly voided treads, as these bald tires supply a lot of real estate for water to withdraw out rapidly.

And Cooper STT Pro is pretty bald. It’s offers very nice grooves in both lengthwise and edgeways direction so both the curved and the straight aquaplaning resistance is achieved, meaning, tire does not hydroplane on curved and straight paths providing good enough float speeds.

Float speeds is the highest speed a tire can execute on pooled water without levitating.

Snow Performance

Cooper Discoverer STT Pro is not 3 peak mountain snowflake rated but the tire’s are great with deeper snowy terrains going up to 5 feet, without any issues.

And it’s a misconception that the tire’s not having 3pmsf rating can not perform on snow.

I mean sure these tire would lack on hard packed snow, and now way you should run them on ice with such limited siping, but they are still good enough in deeper snow.

There, it’s dual layer under it’s ribs are effective on grabbing on to the snow, where the surplus snow gets pulled out of wide lateral passages.

The sidewall lugs and staggered shoulder also act as shovels throwing snow backwards and creating forward momentum.

Tread Life

The balder the tire, the faster the wear, because the left over tread blocks has to bear the same weight of the tire, and when it comes to mud tires, they are the heaviest and the baldest.

In case of Cooper STT Pro that’s 94 pounds we are talking about standing on a couple of tread blocks with wide grooves on sides, though the tire tires to keep it’s weight less by offering just a single cap ply of nylon.

Also here the stiffer composition of the tire also helps, where it’s harder to rub it’s tread off, and with 22/32″ of tread depth at it’s disposal, it still provides good enough resistance to wear.

Moreover, the all of the tread blocks have reinforced foundations, which ensures that the blocks even whist bearing heavy weight of the tire stay firm.

Off Road Traction

The Cooper Discoverer STT Pro are my go to tires for off road. These tires provide amazing traction values on sorts of terrains.

Let’s discuss all of them one after another.

Rock Traction

My go to tire for in all terrain category is Falken Wildpeak AT3w, in rugged terrain, it’s Nitto Ridge Grappler, and in the mud terrain category it’s Cooper Discoverer STT Pro, and I haven’t found another tire that can impress me more than this.

This tire offers the best mixture of lateral and circumferential traction. If you look at the tire’s tread again (scrolling above to the tread section), you’ll see that the tire makes 2 horizontal grooves in a shape of wave, one with slightly smaller tread blocks while other with chunkier.

Both of these provide huge gripping values when the tire moves forward.

Similarly, the sidewall biters, offset edges on both smaller and larger ribs, and longitudinal groves everywhere offer similar powerful traction values towards sideways.

It’s 3 ply polyester casing made sidewall moreover, inspiring confidence, so you don’t worry about getting the tire damaged, while the chip resistance rubber shows you that the tire is not going to wear off that easily.

The sidewall lugs provide this tire with extra footprint, although you don’t need it most of the time, but when you do it’s multiplies it’s gripping capabilities by twice.

Mud Performance

Mud requires efficient self cleaning, as you can’t run a tire which gets packed with mud, that’s because when mud get lodged in the tread, it’s contact with the ground mud just slips, and there’s not way you can move forward.

Now as I explained the lateral grooves the tire makes, these act as paddles much like paddle tires you see which are exclusively made for mud.

So mud simply gets forced out sidewall as the tire moves forward, and aiding to that are it’s bulky staggered shoulders and sidewalls which throws the mud backwards and pushed the tire forward without letting it dig more.

Sand Traction

Cooper Discoverer STT Pro is not good in sand, that the only part, actually where I am not impressed.

That’s because sand is a tough one. Here you need a light tire with good tread print.

Cooper STT Pro offers good tread print, but the tire very heavy, and although it does get the job done when you lower the tire’s pressure down, compared to other MTs it lacks slightly especially on slopes.

Lastly, leave with this

Overall, I am pretty impressed with what Cooper STT pro can do, especially on rocks, where it impresses you the most.

The high durability of the tire is also very confidence inspiring, where you take these tires anywhere carefree.

On mud these tires act as paddle tires and you are not going to have any complaints there, though can’t say the same about sand, though if you are going to run them there, go with smaller load ratings.

Lastly for roads, good enough on dry, but just okay at best on wet. Great with tread, but bad with fuel economy. And noise is okay I guess. But comfort requires getting used to.