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Cooper Discoverer STT
Offroad Tire Reviews

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Cooper Discoverer STT
TEK3 Tire
Ratings (1-5 Star)
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Cooper Discoverer STT On / Offroad Tire Review
The Cooper Discoverer STT On / Offroad Mud Terrain tire is Cooper's answer to the offroad enthusiast's desire for an aggressive offroad tire that performs well in a variety of terrains while still behaving well on the road as a daily driver.  Available in sizes up to 37", the Discoverer STT is a Light Truck class, load "D" radial and is a step up in offroad ability from the Cooper Discoverer S/T.  The Discoverer STT has design features that allow it to compete with some of the more popular offroad tires on the market including deep voids with suction releasing channels for self-cleaning in mud, siped lugs for improved traction offroad as well as on the paved road, tread design extends far down the 3-ply sidewalls for greater sidewall protection and puncture resistance, rim flange protectors to help protect your rims, 3 ply carcass construction called TEK3 consisting of two radial polyester body plies and one angled polyester body ply, which adds up to a strong radial construction.  The tread design is similar to other good performing offroad tires.  Some of the Cooper Discoverer's highlights include a unique center tread area that is composed of non-directional, siped lugs and a leading edge that Cooper claims helps to eject stones.  The outer shoulder lugs are also siped and larger for improved traction in mud and snow.  Shoulder lugs are also notched in their sideway and aid to find traction in deep mud with sidewall bite.  On the rocks the Cooper Discoverer STT does moderately well although a tougher, longer lasting rubber compound reduces traction on rocks to the point where experienced offroaders who have tested the tire on the rocks reported claimed they would slip sideways at times when they expected traction.  However in rock applications the sipes and notched leading edge of the lugs help to provide extra bite, while the harder compound improves long-term wear on the road for an extended life of service.  On the road the tires perform well with only a slight "hum" as you might find with any quality mud terrain tire on the road.  Cornering feels stable and the load range allows this tire to be used for truck tire applications such as towing and hauling loads.  Visually the Cooper Discoverer STT is impressive with a great sidewall profile and sharp, detailed design.  A great all-round tire for the owner in need of both an offroad tire as well as a daily driver.


Manufacturer's Description

Cooper Discoverer STT On / Offroad Tires

The Discoverer STT is Cooper’s premium high void off-road light truck traction tire designed for drivers who want the utmost in off-road traction. It is offered in a wide range of commercial and large diameter flotation sizes and is designed for use on pickups, SUVs and off-road vehicles.


The Discoverer STT’s aggressive tread design extends far down the sidewall of the tire to enhance its soft surface traction and also provide additional “bite” in rock climbing applications.


Strategically placed in the lower side wall area, this feature helps protect the wheel and tire from hazards in off-road driving conditions while enhancing appearance.


An integral stone ejector rib extends down from the center lugs to the buttress blocks to help prevent stones and debris from lodging between the tread elements while contributing to the overall soft surface traction.


The Discoverer STT’s computer designed, non-directional tread employs a combination of features including deep buttress lugs, notched and scalloped shoulder lugs, and a unique center traction zone to create a bold, aggressive tire for tough off-road applications.


The heavy duty carcass of the Discoverer STT is constructed of two radial polyester body plies and one angled polyester body ply to deliver 3 plies of protection for superior resistance to impact breaks and bruising.

Cooper Discoverer STT

1-Ply nylon
2-Ply steel
3-Ply Polyester
3-Ply Polyester


Tire Specifications
Tire Size Service Description UTQG Load Range Sidewall Approved Rim Width Measured Rim Width Section Width Overall Diameter Tread Width Max Load Tread Depth
30X9.50R15LT 104 Q 0   C OWL 6.5 - 8.5 7.5 9.8 29.7 7.8 1985 20
31X10.50R15LT 109 Q 0   C OWL 7 - 9 8.5 10.85 30.75 8.3 2270 20
32X11.50R15LT 113 Q 0   C OWL 8 - 10 9 11.4 31.76 9 2535 20
33X12.50R15LT 108 Q 0   C OWL 8.5 - 11 10 12.08 32.76 9.7 2205 20.5
35X12.50R15LT 113 Q 0   C OWL 8.5 - 11 10 12.2 34.76 10 2535 20.5
LT235/75R15 104 Q 0   C OWL 6 - 7 6.5 9.45 29.09 7 1985 18
LT215/85R16 115 Q 0   E BLK 5.5 - 7 6 8.08 30.63 6.1 2680 17.5
LT235/85R16 120 Q 0   E BLK 6 - 7 6.5 9.7 31.8 7.3 3042 18
LT325/80R16 124 Q 0   D BLK 8.5 - 11 9 13.1 36.78 10.8 3525 20.5
LT225/75R16 115 Q 0   E OWL 6 - 7 6 8.7 29.53 6.7 2680 17.5
LT245/75R16 120 Q 0   E BLK 6.5 - 7 7 9.45 30.7 7.6 3042 18
LT265/75R16 123 Q 0   E OWL 7 - 8 7.5 10.1 32 8.25 3415 18
LT285/75R16 122 Q 0   D OWL 7.5 - 9 8 11.3 33.1 8.85 3305 18
LT315/75R16 121 Q 0   D OWL 8 - 10 8.5 11.92 34.47 9.8 3195 20
LT255/70R16 108 Q 0   C OWL 6.5 - 8 7.5 10.56 30.31 8 2205 17.5
LT265/70R16 110 Q 0   C OWL 7 - 8.5 8 10.94 30.86 8.4 2335 18.5
LT305/70R16 118 Q 0   D OWL 8 - 9.5 9 12 33.07 9.8 2910 19
33X12.50R17LT 114 Q 0   D OWL 8.5 - 11 10 12.54 32.76 9.8 2600 20.5
35X12.50R17LT 119 Q 0   D OWL 8.5 - 11 10 12.67 34.76 9.8 3000 20.5
37X12.50R17LT 124 P 0   D BLK 8.5 - 11 10 13.1 36.9 10 3525 23
LT245/70R17 119 Q 0   E BLK 6.5 - 8 7 9.6 30.7 7.6 3000 18
LT265/70R17 121 Q 0   E OWL 7 - 9 8 10.8 31.9 8.25 3195 18
LT285/70R17 121 Q 0   D OWL 7.5 - 9.5 8.5 11.5 33 8.85 3195 18
LT295/70R17 121 Q 0   D BLK 7.5 - 10 8.5 11.8 33.45 9.4 3195 20.5
35X12.50R18LT 123 Q 0   E OWL 8.5 - 11 10 12.5 34.76 10 3415 20
LT275/70R18 125 Q 0   E BLK 7 - 9 8 11 33.35 8.8 3640 20.5
LT275/65R18 113 Q 0   C OWL 7.5 - 9 8 10.98 32.32 8.45 2535 18
LT325/65R18 127 N 0   E BLK 9 - 12 9.5 13.5 34.75 10.8 3860 23
LT305/60R18 121 Q 0   E BLK 8.5 - 11 9 12.09 32.64 9.8 3195 20.5
LT325/60R18 124 N 0   E BLK 9 - 12 9.5 13.3 33.22 10.8 3525 23
33X12.50R20LT 114 Q 0   E BLK 8.5 - 11 10 12.49 32.66 9.8 2600 20.5
35X12.50R20LT 121 Q 0   E BLK 8.5 - 11 10 12.5 34.66 9.8 3195 20.5
35X13.50R20LT 122 N 0   E BLK 8.5 - 11 11 13.65 34.65 10.5 3305 21

Manufacturer Info:

Cooper Tire & Rubber Company - Findlay, Ohio
Corporate and Tire Headquarters
701 Lima Avenue
Findlay, OH 45840

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User Reviews

Below are reviews by people who have had experience with this tire.  Opinions below are not necessarily that of Offroaders.com.  If you'd like to submit a review of your own, please use the form below to review this tire.  Please restrict your comments to only tires you have had experience with.

Got STT's on the XJ, they're alot quiter than the BFG mud's. Super sticky on rocks.

Frank S.

I have a set of STT 33's on a TJ. Just came back from a 4 day trip, did Taylor, Pearl, Schofield/Punch Bowl(both directions), Lead King, Engineer, California, Poughkeepsie, Corkscrew, etc, all in the rain and sleet. The STT's worked GREAT on every type terrain, including ROCKS!  I've had MTR's and BFG's also and the STT's work every bit as good and are priced right!

I got probably the first set of STT's in Canada. I reviewed them for a can4x4 magazine. Mine arew 30" as they were size limited at the time. I have been running them since April of this year. Nothing but good things to say. they have a pattern very similar to an MTR except these have factory siping. The side biters are nice as are the rim protectors which I have scuffed alot on tree roots etc. My old toyota had MTR's on it and that was a major problem for me was getting sticks in the bead.

They have a slight humm on the hiway but nothing too bad. They also have rock ejectors between the tread blocks that seem to work really well.

Now if they only made them in a 33x9.50 or 10.50 I would get them again.

I have only driven these tires on dry pavement, and had them on a nice trip of about 800 miles of mixed surfaces down in Baja Mexico, including various dirt and sand driving. They are working great on all of those surfaces. No testing on "rock crawling", mud, rain, or snow yet. So there is still a lot of evaluation to be done. (It has been one of the driest winters on record here where I live).

Ride: On road handling is average/good. Noise is not bad, on par with the MT/Rs. Probably between an all-terrain and mud tire. Balancing is great and they are ROUND, unlike the MT/R's I had mounted. These do not hop - they ride nice and smooth at all RPM's.

Fuel economy: No noticeable improvement over the MT/R. This is probably a difficult variable to assess on my truck because it is so bulky/heavy. This evaluation would likely be easier on a more stock configuration truck.

Looks: I think these tires look way better than the MT/R.   - bajataco.com

I have had opportunities to use these tires in rain, snow and rocks since my last post. I am very happy with them in all of these scenarios. I have had them in mud, but hardly anything that would qualify as a substantial test. (and that is fortunate, because I dislike mud driving). I have been really impressed with these tires on the "rock crawling" type of trails. They "hook up" and stick very well for my truck. I was also really happy with them in the snow. I managed to drive some roads and trails where I broke the first tracks, and they did very well.

As for pressures:

I run 34-35 psi on the street. (With my old 32" BFG A/T's I would run them at 32 psi.) Since the lugs on the MTR's and STT's have a bit more resistance (and consequently worse fuel economy) I run them at just a bit higher pressure than an A/T tire.

For trail use, I run anywhere from 20-24 psi for mild trails depending on the surface conditions. For very technical trails on rocks and dirt, or the occassional severely corrugated (or "washboard") roads, I will go down to 17-18 psi. For sand or mud, if 18 psi is not performing well enough, I will go down to 12-14 psi but it is rare that I am in those conditions.

Keep in mind this is for a 32x11.5x15, Load Range "C" tire on a truck weighing in the low to mid-5,000 lbs. range with even weight distribution from front to back.  -  bajataco.com

Photo credit: Casey Campbell, TLCA





Rating  Key - The star rating keys are specific to the terrain being rated in the review.  To the Top 
Don't even consider it if this is your main terrain. This tire will not perform well at all in this terrain.

Its trying but not doing too well.  You'd be better off choosing another for this terrain.

Average.  Its doing ok, not great but its holding its own.  A decent choice if you're compromising.

This tire does very well in this terrain but its not the best tire available however still a very good choice.

This tire performs exceptionally well in this terrain.  Among the best suited for this terrain.

Size Availability - This is a one to three thumbs up snapshot rating where one mean poor selection, two means ok and three means great.  Check with suppliers or manufacturers for actual available sizes.  While this rating system is vague, we couldn't possibly list all available sizes with size selection changing over time.  Please see manufacturer for list of sizes in production.

Money Bags - This is an average cost scale based on an averaged advertised cost of this tire when compared to other tires.  One money bag represents the tire is typically one of the cheapest available while 5 money bags indicates that this tire is one of the most expensive.  Averages are based on the tires reviewed.

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