Cooper Discoverer STT Pro – A Tire Review.

“Those look beastly! How do you like them?” This is a question we’ve received in various forms during our recent travels running the Cooper STT Pro off-road tire. At first we found the question somewhat challenging to answer accurately as the tires had only been recently mounted. It’s difficult to really get to know a product when the testing period only lasts for one trail day, or even a full weekend. Fortunately, our review period is much longer, and after six months, numerous back country trips, and 10,000 rugged kilometers later – it’s a question that is much easier to answer!

 

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Back in June of 2018 Expedition BC entered into a partnership with OutHereAdventure.com – a Canadian overland and backcountry online magazine. Cooper Tires, through OutHereAdventure, shipped us a brand-spanking-new set of five STT Pro’s in our size of choice. The idea was for us to put the tires through their paces, incorporate our experience through our trip reports, and ultimately write a review on our findings.

 

Who Are We?

          First of all, we are not automotive journalists! We are a young Canadian family who just happen to really like camping, off-roading and overland-style vehicle adventuring. We manage to get out a lot, sometimes spending as much as two months per year living out of our adventure truck, travelling all around western North America. We mainly spend our time covering the trails and back roads of British Columbia and Washington State. In recent years, however, we have explored as far away as the Arctic Circle in Alaska, Northern Manitoba, the high mountain passes of Colorado and red rock of Moab, etc.

 

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Our trip reports are photo-heavy. They are published for family and friends, as well as readers who enjoy following along and sharing in our experiences.  We tend to avoid pavement and like to camp in remote areas away from cell phone coverage and established campgrounds. We figure that there is value for you, our readers, from us sharing our perspectives on running this tire through the lens of a regular 4×4 enthusiast. It is also important to note that we do not have any direct or formal affiliation with Cooper Tires.

 

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The Numbers and Specs:


          Cooper offers the STT Pro in numerous sizes, varying in overall diameters from 30 – 38 inches, and wheel diameters between 15 and 22 inches, respectively. In the majority of sizes, the load range is “E” and “D”, however there are lighter duty options available in certain sizes. Our designated tire size is 285/70R17. This is roughly the metric equivalent to a 33″ x 11.5″ tire, and is a common size for many trucks upgrading to a slightly larger size over stock. These are load range “D” and each tire weighs 62 pounds. They are rated for M+S (Mud and Snow), which is important for provincial or state laws, such as here in British Columbia, which require all vehicles on mountain highways to be equipped with M+S or winter-designated tires during the winter driving season.

 

Technology Features:

          The STT Pro’s have several features to make them an option that stands out in a large market. For sidewall durability, the ARMOR-TEK3 protection is interesting as the 3rd layer, or ply, in the sidewall runs at an 8 degree angle to the first two layers. This creates a bit of a diagonal pattern in the cords, creating extra resistance to punctures, and is unique to Cooper. We especially appreciate this feature as a punctured sidewall equals the death of a tire, compared to a puncture in the tread which can be repaired on the trail.

 

 

 

 

 

 

The tire also has an alternating pattern of 2 and 3 inner tread blocks which helps to decrease road noise. The pattern works, as we have been pleasantly surprised to find tire noise to be equal to the Goodyear Duratracs we were previously running for the past 100,000 kms over two sets (same tire size). If you aren’t familiar with the Duratracs, they are neither as durable or aggressive as the STT Pro’s, so it was a nice touch to not have increased noise in our Sequoia used for daily driving.

 

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You’ll find elevated strips in the depths of the tread valleys, designed to prevent small stones lodging in between the treads. This was an issue we experienced with our Goodyear tires as our farm has a gravel driveway and the rocks were constantly getting stuck between the tread blocks. The Coopers also have mud dimples built into the sides of the tread blocks, designed to prevent the valleys from getting caked up with mud. In our travels in the snow, we’ve found these also help to keep snow from filling up the valleys as well.

Many of the tread blocks are also siped (small lines cut into the smooth part of the tread contacting the road surface). This is done to increase traction on wet and dry pavement, another feature supporting the use of this tire for a greater range of driver’s needs.

 

Our Test Vehicle:

2003 Toyota Sequoia 4.7L V8:

– Part time 4×4, low range transfer case
– Independent front suspension, coil springs
– Open front differential
– Solid rear axle, coil springs
– Open rear differential
– “Locking” centre differential (eg: Lexus GX470, Landcruiser 100 etc.)
– Electronic traction control always OFF
– Front sway bar disconnected full time
– Mild suspension lift
– Average 6,000 lbs curb weight as tested
– 285/70R17 tire size as tested (roughly 33” x 11.5”)

 

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The Sequoia, previously on Goodyear Duratrac tires

 

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Pulling our Kakadu Bushranger trailer through Southeastern Oregon

 

          Of note: During the testing period, we alternated between no trailer, and towing either our 1500 lb. Kakadu Bushranger off-road trailer or our 3500 lb. lifted Jayco travel trailer.

Performance Testing:

          One of the benefits of a long-term road test was being able to experience such a great variety of terrain and road surfaces. We attended both the Northwest and BC Overland Rallies and drove the obstacle courses at each event without issue. Towing our lifted Jayco travel trailer, we toured the twisty highways and forest roads of the Cascade Mountain Range in Washington State. We also spent four days towing our Kakadu Bushranger off-road trailer on a nearly 400 km off-road route from BC’s Fraser Valley to the interior of the Province, exploring BC’s gold country. Temperatures on the trip hit 40 degrees Celsius (104 F) and we drove on silty sand, river rock, and even over numerous prickly pear cacti (yes – Canada has cacti!).

 

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I also went on a week-long solo trip into some of the most remote areas of Southwest British Columbia, punishing the Coopers as the Sequoia crawled its way to the top of Poison Mountain, and through 100 foot long water crossings through the infamous Mud Lakes region.  I then returned to the area in October, guiding six trucks for five days over the Yalakom-Big Bar traverse, encountering deep snow and temperatures as low as -17 degrees C (1 degree F) and many grease-like muddy two tracks.

 

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In between our overland and off-road trips, we’ve used our truck as a family hauler and daily commuter, driving the twisty highways and rainy west coast streets around Vancouver. In short, we can confidently say that we are familiar with the performance this tire offers.

The Result?

          The Cooper STT Pro is an impressive package and all around tire. Off-road traction in dirt, mud and even deep snow was superb. Without traction control engaged or any lockers on the axles, our Sequoia is actually a pretty basic 4×4 machine. There was numerous times where the Coopers dug in and clawed their way over obstacles, saving time and ego by avoiding use of recovery gear and winching.

 

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There were a few situations where we found ourselves especially impressed with the amount of traction. The first was on a muddy and wet trail junction on a trip to Cabin Lake, a lesser known alpine lake destination at the end of a maze of logging roads and tight trails in the mountains of BC. The Sequoia was off camber with a front wheel up in the air and came to a stop. With a firm push of the right pedal, the rear tires flung a rooster tail of muddy soil up in the air, allowing the truck to climb back up onto solid ground and continue on – something I was not expecting.

 

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Another moment was driving in deep snow on a wind-crusted two track over the China Head traverse. The truck was forced to follow along in the snow ruts, and I was trying to turn out of them to drive on fresh snow – a situation I’ve been in many times with the Duratracs, only to find myself bouncing back into the rut. With a hard crank of the wheel, the Cooper’s aggressive sidewall lugs bit the crusty snow edge and pulled the truck into the fresh untracked snow. This was a somewhat unexpected success, as again I was used to the Duratracs with mostly cosmetic sidewall lugs.

Of course, a tire designed with extreme off-road traction and durability in mind will give up some other performance attributes. One of the first things we noticed after having the tires mounted, was the impact in acceleration and fuel mileage. Increased durability usually means extra heft. At 62 lbs per tire, they were noticeably heavier than the tires we had been used to for so long. This extra weight is felt when accelerating from a standstill, and noticed when calculating our miles-per-gallon. On average, we calculated a 1-2 mpg loss, depending on the type of roads driven. Other than those two issues, which can be expected given the intended use and performance of the tire, we really couldn’t find any other negatives for the STT Pro.

 

 

 

Given that these tires are for trucks, and for trucks meant to leave the pavement, a slight loss in acceleration and fuel mileage is a small compromise to make, considering the traction and durability you gain where it really counts.

On-road performance was equally as impressive. Fully loaded with family, gear and trailer, the Sequoia confidently carved up the turns on the highway between trails. If you’ve ever driven Hwy 12 between the towns of Lytton and Lillooet, a sad excuse for a provincial highway, you’ll appreciate the unexpected amount of cornering ability the Coopers offer.

Also, not that it really counts much, but the Cooper is a handsome tire. We actually received several comments on how well the tire looked on the Sequoia. We can’t count this as a performance positive, but it doesn’t hurt to like the way it looks!

 

Durability and Value:

          After 10,000 kms, our tread depth measured at 16-17/32’s all around, which we were quite happy with as new tread depth is 19/32 inches. Considering how we thrashed them during the testing period, they have held up well. At this wear rate they are projected to last us for 75,000 – 80,000 kilometers, or about 45,000 – 50,000 miles. This is good value for an off-road tire in this performance category.

 

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It’s often said, that your tire is the only part of your vehicle that actually touches the road. This is an important concept, with the idea being to not cheap out on those overseas options, or remaining with your factory tire options if you plan to leave the pavement regularly. If you are traveling the back country, a good tire will inevitably pay for itself. Just think of the cost of a tire failure, off-road vehicle recovery, or even the value of an unplanned night in the bush because you got stuck when you shouldn’t have.

With the Coopers, we purposely scrubbed the sidewalls on boulders and stumps and aimed straight for those pointy and sharp looking rocks sticking up on the trails during the testing period. An up close examination of the tires shows no major tears, missing chunks or gouges – a testament to their toughness. We did not experience any punctures or loss of bead during our harsh testing.  While we’ve never had a flat with our Goodyear Duratracs (likely due to religious airing down and avoiding sharp rocks), our old set is in the garage, and they are littered with gouges in the tread, and slices and chunks of the sidewall are missing. This was an eye opener for us. It’s hard to put a monetary value on knowing the tires you are rolling on – the only part of your vehicle in contact with the ground – are absolutely solidly built and rugged as hell.

 


PROS:  Awesome off-road and on-road traction on various terrain. Extremely durable, a tough tire. Available in many sizes. They look great.   

CONS:  With durability comes extra weight. Slight loss in acceleration and miles-per-gallon observed.


 

 

Who Is This Tire For?

          The Cooper Discoverer STT Pro is described by Cooper as their most extreme all season and off-road tire they offer. That may sound like they are too aggressive to run on your daily driver / weekend warrior vehicle, but thankfully that is not the case. From our experience, there is no doubt that this tire exhibits absolutely solid off-road performance over various terrain.

 

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Typically, the downfalls of great off-pavement traction are poor tread wear, extra noise, and below average road performance (wet or dry). Cooper has managed to cleverly mitigate these downfalls, without sacrificing what the tire was designed to do in the first place – grip the dirt, fling the mud, and crawl up and over the rocks with unwavering confidence.

Because of this, we would recommend the STT Pro’s for a wide-variety of applications, from dedicated four-by-fours, weekend warriors, hunting rigs, overlanding, and anyone who needs a tire that will absolutely not let you down.

 

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In Conclusion:

          We will continue to run the Cooper Discoverer STT Pro’s on our adventure truck. With plans to return to the Arctic for several weeks this fall, as well as an upcoming three-month long journey across Canada from coast to coast, we are confident that the STT Pro’s will see us through.

If you want to read more about the Coopers, and see what sizes are available, click HERE.

 

-written by Jay of Expedition BC – http://www.xpedbc.com