Trail Review: Cooper Discoverer S/T Maxx

Cooper Discoverer S/T Maxx (All-Terrain/ Mud Terrain Tires) – Review on 5th Gen 4Runner

With a new 4Runner in my life and a lot of places to see, I knew that the first and most important upgrade was a new set of tires. I wanted a tire that would cover rugged terrain in varying conditions while still remaining civil enough on the road for the long hauls from where I live to where the dirt starts.

In general, mud-terrain tires perform very well off-road but will ultimately suffer with on-road performance due to their blockier design and larger lugs. On the flip side, an all-terrain or all-season tire will perform much better on-road than their mud-terrain brothers, but they will fall short in rougher conditions off-road especially in slick/muddy situations.

Que the Cooper Discoverer S/T Maxx.

  • Type: AT/MT  – All Terrain Hybrid
  • TireRack.com (285/70R17): Check Price
  • Amazon.com (285/70R17): Check Price
  • Tire Buyer: Check Price
  • Americas Tire: Check Price
  • Cooper: Check Specs
  • Size Offerings (17″ Wheel):
    • 235/80R17
    • 255/80R17
    • 245/75R17
    • 255/75R17
    • 285/75R17
    • 245/70R17
    • 265/70R17
    • 275/70R17
    • 285/70R1
    • 295/70R17
    • 315/70R17
    • 265/65R17
    • 305/65R17
    • 37X12.50R17

Stuck between a mud-terrain and an all-terrain style tire, the S/T Maxx skillfully balances the duties of both an on-road and off-road performer. With a tough carcass at its heart, the tire delivers confidence on the trail even in the toughest conditions.

I have had these tires on the 4Runner for the last 3 years in the 275/70R17 size and have covered fifty-five thousand miles. Based on where I have been with them I’ll break down my thoughts into a few basic categories: on-road performance, off-road performance, and long-term wear.

On-Road Performance

On-Road Performance Cooper ST Maxx

It’s a simple formula, the more aggressive the tire, the louder it will tend to be and the worse that it will handle on the road. Just talk to anyone with a set of dedicated mud-terrains and they’ll agree. I have found the Coopers to be surprisingly quiet through my run with them.

Only in the last five to seven thousand miles have I started to notice a hum which I attribute to my alignment being slightly off. Even with the less than ideal wear that has started to develop, the hum and vibration that they have is mild compared to others I have had in the past.

I am a weekend warrior by passion

This means that when I do get out to where the pavement meets the dirt, there is usually quite a lot of paved driving required to get there. I wanted to make sure that the tires I put on the 4Runner would not only be able to stand up to the rigors demanded on dirt, but that they would perform equally as well on the roads getting there.

Inflated to between thirty-eight and forty psi, the Coopers handle as confidently at seventy miles per hour on the highways as they do through the twists and turns of the Sierra mountains. I will admit, when I first had them installed they felt a bit “squishy” and it took a few hundred miles for them to feel right in my mind. But once they firmed up, my confidence hasn’t wavered. Even under hard braking, they will hold a straight track.

A True All-Terrain tire

In the snowy conditions, Cooper ST Maxx

In adverse weather on-road, the Coopers show that they are up to the task.

In rain and standing water, they track true and only when acting recklessly do they show their susceptibility to the common hydroplane. But even that took some effort on my end, as I tested the limits of the tire to know how far they could be pushed.

In the snowy conditions, they really shine.

From hardpack to deep powder they grip far beyond what you would expect. On one trip, my unchained tires kept up with a few buddies that were partially chained to get through some slicker snow conditions. Their only winter drawback is ice.

However, unless you have dedicated snow or studded tire any tire will suffer on ice. For me, that’s ok because I stay aware of the changing conditions in the mountains during winter and adjust my driving habits to compensate for the potential lack of traction.

And I always carry a set of chains in the snow to stay safe when conditions call for them.

Their tendency to pull right

One thing to note about these Coopers on the road is that they have a tendency to pull to the right on the highway. Now, I have gotten quite used to it and just consider it par for the course. But there are other people I know that can’t handle constant pull/correction. Really, you won’t know where you stand until you try them yourself.

I would recommend that you have a tire shop that will let you test drive for a few hundred miles install your tires so if the pull is too much, you can try a different tire.

Off-Road Performance

Cooper ST Maxx Off-Road Performance

Performance off the developed path was the main reason I wanted to upgrade the tires on the 4Runner from the get-go.

Stock tires are… well… stock. They are meant to be used primarily on the road and are designed for comfort over off-road capability. In my experience and research, I have found that the most common point of failure off-road is a punctured or ruptured sidewall.

This is one of the main reasons why even those with light-weight off-road vehicles will opt for a higher load rated tire. Additional plys in both the main tread and the sidewall prevent punctures and slices and keep your trip going without a hitch.

Coopers are well known for their tough carcass, on this tire known as the ArmorTek3® and it doesn’t disappoint. I have had these tires aired down and punished over many miles of gravel, rocks, roots, sand, snow, mud, you name it. I haven’t had any air loss or failures through all of it.

Rocks and gravel performance

Rocks and gravel performance - Cooper ST Maxx

Across rocks and gravel, these tires perform very well while resisting cutting and chipping that is common with softer compound tires. The added confidence from the thicker sidewalls help when traversing desert roads where sharp “sidewall biters” are very common, or on forest trails where worn tree roots can easily cause a sidewall flat.

The semi-open tread pattern allows for great traction on loose surfaces, but enough void to shed mud of every type but clay. Aired down to eighteen to twenty PSI the thick sidewalls give enough flex to soften the ride on washboard roads, and crawl over rocks and wet logs without slipping.

I personally have admired these tires for their complete versatility off-road and their ability to keep the show going when faced with challenging terrain.

Long-Term Wear

Long-Term Wear

From Cooper, these tires come with near as makes no difference 9/16” of total tread depth. As it sits today, there is about 4/16” left on all 4 tires. That would be impressive for a typical mud-terrain tire with thirty-five thousand miles.

What makes these tires different is that they have just over fifty-five thousand miles on them. Good tire wear is crucial when they cost as much as they do, and when their performance is measured by the amount of tread remaining. With roughly 1/16th of an inch of wear for every ten thousand miles, you’ll get a lot of adventures out of a set.

Minor chipping or cracking after 3 years

Minor chipping or cracking after 3 years

Aside from the wear itself, these tires have very minor chipping or cracking after 3 years of them being on the 4Runner.

Minor cracking on the edges of the side lugs are not uncommon for tires that are put through the paces and are usually associated with age.

The chipping that has happened has been infrequent and usually in places with an abrasive rock parent material. From the photos shown you will see that at fifty-five thousand miles the tread is solid, with more life left in them for future adventures.

Conclusion

These tires were the first, and to this day, arguably the best modification that I have made to the 4Runner. They have greatly expanded the capability of the vehicle, and made the ability to travel to remote places easy and reliable.

I have never been let down by the S/T Maxx’s and they continue to perform on the vehicle as intended. When the time comes to replace the set, likely before the winter, I will be replacing them with their skinnier cousins the 255/80R17 S/T Maxx.

I will also be adding a full size matching spare wheel/tire combination to the 4Runner to allow for a 5 tire rotation and a reliable back up if needed on the trail.

I am changing tire sizes only because I have lifted the 4Runner since installing the first set of Coopers and can now afford the taller tire.

But the question of whether or not I will be purchasing a different tire has never come up on my mind.

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Tim
Tim
2 months ago

Hello,
Reaching out to you with a question regarding unusual tire wear on my 275/70/17 Cooper Discoverer ST Maxx.
I had the tires installed 5,500k miles ago on my 2018 4R and just had my first tire rotation done at my local Americas Tire. I was informed that my front tires were cupping badly and that my rear tires were completely fine. I had an alignment done at my local Toyota dealership the same week I had tires installed so I know alignment was good from the get go. I recently went back to Toyota to double check the alignment and they said it was still ‘dead on’ and no adjustments were needed. Strange that they are cupping so soon or at all for that matter.
With this set of tires I have done very little off roading and have done mostly freeway driving this far. I run my tire pressure at 35psi. I run Icon CDCV coil overs and have them set all the way around to 7, not too firm not too soft. I also had my front coils preloaded just under 2″ which I recently backed down to 1 1/4″ to see if maybe this was causing the unusual wear. I also have JBA UCA’s and a diff drop. (just to give you an idea of my setup) I also re-torqued all suspension bolts 3 times this far and have found nothing out of spec. FYI…My previous KO 2’s did not start cupping until 37k.
With that said, have you experienced this type of wear with Cooper ST Maxx tires or have any suggestions or advice on what may be causing this unusual wear ?

Vince
Vince
3 months ago

Hey Max, Considering these tires for my 2020 Off Road. Did you say you were at stock height when reviewing these? I noticed Kings in the photos… Trying to gauge how they’d look with my 6112/5160 2/1 inch lift.

Hans
Hans
11 months ago

Did you fit these while stock? Any modifications needed to go 275?

Russell
2 years ago

These replaced the K02s that came stock on my Raptor after they chunked to the point of ruin on my last high-speed off road run. Other than being a tiny bit noiser and 2lbs per tire heavier, these greatly exceed the K02s in every other aspect – even fuel efficiency! Traction in all conditions and surfaces is much improved, and despite running fast over the same rocks that annihilated my K02s last time, they barely show any wear, other than slightly increased siping width. Very pleased.

wayne feller
wayne feller
2 years ago

just got these tires a couple of weeks ago and a tire pull to the right was evident from the start and a couple of rotations have not remedied. Do you have other sources of information that suggests the tire pull is just inherent to this tire??? My Discount Tire is about to order a new tire, thinking that one of them has a radial pull caused by a manufacturing defect.

JP Kee
JP Kee
2 years ago

Are you running these at around 38 psi cold?

Augie
Augie
2 years ago
Reply to  JP Kee

I keep them at 40 nominal, so mostly highway driving, when I’m hitting dirt roads a lot may drop them to around 32, on tough roads down to 25-27

Jim White
Jim White
2 years ago

Did you ever end up putting on the 255/80s?

C

Lee LaCombe
Lee LaCombe
2 years ago

Being out in the middle of the great prairie, the off road adventure will be mostly confined to B roads and cow paths. Nothing extravagant, as a rule. However, if the opportunity presents, I’d rather not be restricted by my tires. Thoughts?

Lee LaCombe
Lee LaCombe
2 years ago

One thing that has bothered me about my ‘18 TRD Off Road is that it comes with tires with a tread pattern that would be at home on an Impala. I have been researching suitable replacements and the 275/70-17s seem like a logical option. I have a Icon Stage I kit in the garage, waiting for a couple of days off to install. Even with that, it sounds like I need to chop up stuff to go with 285s and I’d rather not. I looked into KOs, but apparently an E rated tire isn’t super desirable. The ST Maxx sounds good, but the “pulls to the right” thing doesn’t sound too appealing. The Discoverer doesn’t look aggressive enough…. is there an uncomplicated solution?

jose
jose
2 years ago
Reply to  Lee LaCombe

look into the ko’2 ,I just install them on my 4runner a little rub but I use a heat gun to push the plastic . 275/70/17

Mario
Mario
2 years ago

I think I got a great deal, purchased them in 245/70R16 for my 2005 Pilot for $399 from a wholesaler and $50 installed. I was hesitant due to Tread wear life not indicated in Cooper’s website. Thanks for your review.

jose
jose
2 years ago

how about if I wanted to go with trd wheels how wide can I go

jose
jose
2 years ago

I wanted to know how wide I can go on the stock suspension on a 2017 4runner limited

Augie
Augie
3 years ago

Curious why you had 275/70R17 before your lift and not 265/70R/17 which is the stock size for 5th gen. Also I only see 265 on America’s tire website. Any clarification would be appreciated in the market for tires on my 2015 TE

Mike
Mike
3 years ago

Where are you going to mount the spare tire?

Mike
Mike
3 years ago
Reply to  Max Sheehan

I am currently running 275/70R18 Cooper ST Maxx’s they came with the vehicle when I purchased it two years ago. When I crawled under my 4Runner sometime ago I didn’t think there was enough room to mount a 33 inch diameter tire under it but next time I am looking at my brakes I will test it out. Being able to put 33 inch tire under the vehicle would save me the cost of a rear bumper or having to heave it on to the roof.

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