Cooper Tires’ Discoverer S/T MAXX has been my favorite commercial traction/hybrid tread design since its introduction. I have experimented with four sizes on four different truck platforms, and suggested them to many friends and acquaintances. Two of my four-wheel-drives are still running the S/T MAXX, including the built, 2006 V-8 Toyota 4Runner with 4.88:1 gears in this video.
After a whopping 7,436 miles before the first rotation, mostly road miles, these LT285/75R16 Discoverer S/T MAXX are wearing impressively well and evenly. From their original, generous depth of 18.5/32″, the fronts are down to 16/32″, and the rears 16.5/32″, 2.5 and 2/32″ respectively. That’s an average of 3,300 miles per 1/32″ of tread, and excellent wear from a fairly aggressive, moderate-void tire on a full-time four-wheel-drive car. They were rotated using the rearward cross pattern.
Most light-truck tires are welcome in my garage, from tame all-terrains to the impressively streetable modern mudder. However, I have a strong preference for rubber that fit neither category, those that intentionally blur the lines of distinction, finding their own focus. Known by their traditional name, commercial traction tires, or aggressive all-terrains, hybrid, or the newer slang moniker, tweener (in-between), the design goal is similar.
Commercial traction tires are not new, they have been produced for decades, though the choices were fewer and they rarely received much marketing budget. Still not necessarily the beneficiary of the biggest advertising campaigns, depending on the brand, the performance advantages of modern hybrid treads have won-over many enthusiasts as a practical choice with fewer compromises. This segment of the market demands good grip on multiple surfaces, load-carrying capability, and puncture resistance.
Notably better in sloppy stuff than a typical all-terrain, with less noise and superior versatility than muds, there is much to like. Some have more sipes and the 3-peak/snowflake winter rating, while many don’t, but still perform well in the wet stuff. Nearly all have prodigious tread depth and void—particularly at the outer lugs—that broadcast their ability to absorb and fling muck when required. Mud-terrains are often described as 20/80-designs (20% road 80% dirt/mud), but commercial tractions are generally 60/40, 50/50, or 40/60, depending on their characteristics.
Mastercraft Courser CXT
In May 2016, Mastercraft Tires introduced their new light-truck (LT) commercial traction tire, the Courser CXT. It’s a mid-void, 4-rib that replaces the Courser C/T (C/T = commercial traction). Mastercraft is a subsidiary of the Cooper Tire & Rubber Company, one of the few remaining American tire companies and manufacturers. Before sharing my observations and insights, what Mastercraft says about their product is quoted below in orange:
The Courser CXT was designed as a premium light truck commercial traction tire that provides trusted all-terrain performance with enhanced off-road durability. The CXT features variable full depth siping and a silica rich tread compound for enhanced wet and winter traction. The large tread element and blocky design help to resist abnormal wear while enhancing tread stability and durability.
Large Surface Area Tread Blocks
Provide increased grip on and off-road while improving wear performance.
Optimized Void-to-Rubber Ratio
The amount of rubber on the road is optimized to provide rough terrain traction and enhance on highway driving comfort and feel.
Enhanced Upper Sidewall Design
The shoulder design increases off-road traction with side traction blocks and the circumferential raised rubber feature protects against sidewall abrasion and impacts.
Large Shoulder Scallops
The scallops provide a “mud-scoop” effect for dependable off-road traction while giving the CXT a more aggressive look, to enhance the appearance of almost any light truck vehicle.
The CXT is offered in 29 sizes, starting with the oldie-but-goodie 31×10.50R15LT, up to the 35×12.50R20LT. The size breakdown includes three 15-inch (all load-range-C), nine 16-inch, nine 17-inch, five 18-inch, and three 20-inch sizes. All sport a substantial 18.5/32-inches of tread depth, offering potentially more grip and longevity than others that start with less. In addition to the M+S rating, the CXT can be studded.
For those familiar with Cooper’s other LT designs, it is easy to assume that the CXT is simply a different tread slapped onto their extremely popular and capable, Discoverer S/T MAXX casing. Not so, they are different tires, both tread and carcass. Yet, many considering the CXT will likely also consider the S/T MAXX.
Mastercraft CXT vs. Cooper S/T MAXX—Two Primary Differences
The Discoverer S/T MAXX employs Cooper’s Armor-Tek3 carcass, a 3-ply sidewall, whereas the Courser CXT uses a 2-ply design. There are pluses and minus to both depending on one’s needs; 3-ply sidewalls are generally more rugged and stiffer, where a 2-ply may flex better, ride softer, and weigh slightly less.
The S/T MAXX is optimized for severe cut and chip resistance. When the MAXX was added to Cooper’s light-truck line it’s closest sibling was the S/T (no MAXX), which was/is not nearly as cut and chip resistant. The Discoverer S/T is also a straight 4-rib, where the MAXX’s center alternates between four and five.
The CXT has extra silica for additional wet traction. The slightly higher-void of the 4-rib CXT is visually similar to the older Cooper S/T, but the CXT has deeper scalloped outer lugs, plus beefy upper-sidewall (shoulder) tread that the older S/T does not.
More or slightly less void, 2-ply or 3-ply sidewalls, increased wet traction potential or optimized cut and chip resistance…only you can decide.
Cult Of The 255 / The Third 255/80R17
Several of the 29 Mastercraft Courser CXT sizes could fit one of my vehicles, and I was tempted to pick a larger size. However, for nearly two decades I’ve run and been a fan of moderate width tires, chiefly the 255/85R16, and for a few years its 17-inch brother, the 255/80R17. Mastercraft makes the CXT in both of these sizes, and 255/8x aficionados are surely rejoicing!
One challenge for those wanting to move to the 255/85 size is the lack of treads with less void; many current 255/85R16 offerings are mud-terrains. The 255/85 has become a niche choice, with few newer trucks using 16-inch wheels. The 255/80R17 is even more specialized. Mastercraft’s introduction of the CXT raises the total number of tires offered in this size to three. Cooper makes two of them; BF Goodrich’s mudder is their only competition.
Height, Weight, Width
A super-clean set of fourth-generation Ram 17×8-inch WFK forged-aluminum wheels were purchased from a Craigslist seller, each weighing just 21.8 pounds with the hubcap. Unmounted, a 255/80R17 CXT registers 55.2 pounds on my shop scale (the same size S/T MAXX is 58 lb.), and once mated to a WFK wheel the combination measured 77.2 pounds. Inflated to the maximum 80 psi, the overall height was 32 15/16-inches, with 8-inches of tread.
It’s noteworthy that I’ve repeatedly found published specifications for Cooper-manufactured tires to be accurate. For this tire and size, on a 7-inch wheel, Mastercraft lists overall diameter of 33.15-inches, and tread width of 8.07-inches. Acknowledging that manufacturers’ measuring tools are likely more accurate than my straightedge and yardstick method, and the 255/80 CXT was mounted on a wider wheel, my measurements were still within nearly two-tenths. For the curious, the unmounted height was almost a half-inch shorter, but focusing on unmounted diameter is pointless: tires are not used without wheels and compressed air.
Mounting And Balancing
Manufacturing tolerances, weight, width, construction, and the wheel employed all affect how easily and well an assembly is balanced. In general, smaller and lighter equals easier to true. Using the static, single-plane method, the ounces of wheel weight required were:
The tires were immediately put to work supporting a maximum load on a built Ram that typically lives at its 10,000-pound Gross Vehicle Weight Rating (GVWR), carrying a Hallmark Milner camper, tools, and other supplies. With the fronts at 60 psi and the rears at 80 psi, the ride was neither mushy nor harsh. Over a familiar section of freeway where expansion joints can induce freeway hop (generally not a problem on this truck) the CXTs exhibited no such tendency. Steering response was excellent, a common trait with narrower tires, as they take less energy, time, and effort to change direction. Even at paralegal speeds, balance didn’t change and no bad-vibrations were felt.
Initial impressions were that noise is slightly more than the popular Cooper S/T MAXX, which is an impressively quiet design. This is not surprising as the CXT has a higher-void, 4-rib pattern instead of the MAXX 4/5-rib. The volume and deeper tone is not annoying or loud, and what I expected; both are certainly much quieter than any mud-terrain. The CXT sounds similar but slightly quieter than the older CooperDiscovererS/T (not to be confused with the S/T MAXX, STT or STT PRO).
Function is more important than form, but many like their 4WDs to look tough. Before receiving this set of Mastercrafts I’d not seen the tire in person, just the few marketing shots online. There were no substantive professional reviews or user reports. This article still may be the first. The outer lug scallops were a pleasant surprise, and the sidewall shoulder tread was beefier than I expected. Pretty sexy, in a nice, girl-next-door way.
Notes On Tracking
When changing to a different tread, size, and/or wheel, there is a possibility that your vehicle may need a custom alignment to match the new combination to the chassis. Some folks are willing to ignore a little drift (or pull) right or left, where others find any drift unacceptable. Some tires have a well-deserved reputation for directing vehicles to the shoulder or median, but different trucks and roads can cause different behaviors.
If your truck has an independent-front-suspension (IFS), adjusting the caster (and to a lesser extent camber) to help it track straight should be easy for a good alignment shop willing to make custom adjustments. Be willing to pay more. Finding such an establishment with a skilled technician may be challenging. Many places that should know better still want to use the factory geometry for modified rigs when different settings would fix or dramatically improve drivability.
Picking My Own Line
The 2014 Ram initial CXT test platform has a Specialty Products Company (SPC) 1.5-degree offset ball joint at the right-front, installed after only 1,500 miles to counteract the characteristic right-pull of many Ram trucks and/or some tires. Before any modifications, still running the stock Firestone highway treads, this truck drifted right and would head for the shoulder quite rapidly if the steering wheel was released, typically in six seconds or less. Unacceptable.
The SPC offset ball joint increased caster angle on the right, effectively directing the truck left helping the chassis drive straight without input from the driver to correct the right drift. With such an aggressive geometry modification there is always the possibility, even likelihood, that the truck will track left with some tires or under certain circumstances, including differing road crown. This was a compromise I was willing to live with, but it’s not for everyone. Swapping ball joints is not a trivial affair on a live-axle truck.
With the CXTs mounted, this truck has a slight tendency to go left, depending on the roadway. However, three “look mom, no-hands” tests during the first 100 miles, under suboptimal windy freeway conditions, achieved 12.06, 11.90, and 12.26 seconds before semi-autonomous driving had to be curtailed to prevent the truck from changing lanes. These are good numbers, but not surprising as narrower treads generally track (much) better than wide ones. This also means I’d be perfectly happy to run these on long road trips. The stars were aligned during another test on Interstate 5 in California where I clocked 25 seconds of straight tracking. A buddy’s Dodge that drifts right with most tires, still did with the CXTs mounted . Your truck may vary; adjust as needed.
With all my posts about tires it’s not surprising that I receive mail asking for opinions and advice on tires. A gentleman named Guy from Washington recently asked for my input. Below are his questions and my replies. My review and comments on the 255/85R16 Toyo M/T on my old F-350 will continue.
Howdy, hope you can help me a bit with a tire selection dilemma: 2012 two-door JK, that I use as a daily driver here in Wenatchee, Washington. Also do a couple of road trips every year, 2000 – 3000 miles each. Hunting. Fishing. Some overlanding. Did the 600 mile WABDR this past summer. I’d like to use the same tires all year, snow, rain, heat.
The two-door JK is a nice platform, I was shopping Jeep JKs online just a few days ago, including the two-door models. Sounds like your Jeep sees a nice mix of uses. As much as I’m a tire aficionado who tests and often owns more than one set of tires for a particular platform, there are advantages to picking a set of all-around treads and using them until they’re ready to be replaced.
Very basic Jeep. Manual transmission, 4.10 gears, aftermarket air lockers front & rear. 1.5″ Teraflex leveling kit (springs).
Sounds nicely set-up. There’s much to be said for lower lifts, and I love manual transmissions. Aftermarket selectable air lockers, presumably ARB Air Lockers, are accessories that offer a level of control over traction and wheel rotation that is only available with selectable lockers.
I bought a set of used 16×9″ rims and E-rated 265/75/16 BFG AT’s a week or two after I got the Jeep. Killer deal, $1k for five rims and tires. I’ve put another 25,000 miles on those tires, and they’re getting worn. So I need tires soon. I could just replace them with more 265’s, but they’re a little short.
Several years ago the first aftermarket tires I put on my V8 4Runner were 265/75R16. I agree that 265s are a bit short, most are notably smaller than 32-inches tall. Depending on the tire and tread chosen and the actual height, the advantages to stepping up to a 33-inch-tall tire are quite noticeable. Even with a short thirty-three (32.8″) the approximately one-inch in overall diameter will lift your Jeep a solid half-inch, everywhere. The best lift is tire lift.
I like the 255’s, roughly 33×10’s. Nice! But, I’m afraid they won’t work with my 16×9’s.
You are correct, in addition to being too wide according to the tire manufactures, a 9-inch wheel is a poor choice for a 255 tire for our uses, while a 7–8 inch wheel would be prefect. A 9-inch wheel is also wide for a 265, I prefer to run a 265/7x tire on a stock 7–8 inch wheel. I’ve not shopped for Jeep wheels recently, but I’d image there are many high-quality, original equipment, aluminum take-off wheels for sale on Craigslist. I’ve been a huge fan of the 255/85 size since the early 1990s and have been using them steadily on at least one of my four-wheel-drives since 1998.
Simple solution is just 285’s, but… I fear that’s an awful lot of tire for a little two-door JK… Maybe ditch the 16×9 wheels? I do like the way they look, but I could swap to a more narrow wheel & tire combo happily.
Surely 285s will work on your 9-inch wheels and that is a simple solution. Tread choices in 285/75R16 are almost endless. However, I’m not a fan of using wheels that are on the wide end of specifications. For 285s I prefer to run a 7.5-inch (the minimum) or 8-inch wheel, both for how the tire fits the wheel and the narrower overall width. I don’t care for tires and wheels that protrude further than necessary. I’ve run a few sets of 285 tires over the past several years out of necessity or a desire to run a particular tread that was not available in a 255, but I’d almost always prefer a 255/8x if I could get what I’m looking for.
Ditching the 9-inch-wide wheels would be my suggestion regardless of what tire you purchase. Choosing wheels that are at least 7.5-inches wide but no wider than 8-inches, will allow you run any of the tire sizes we are discussing here; 265/75R16, 255/85R/16, or 285/75R16.
Have four heavy-duty old style tire chains that are a little big on 265’s and fit 285’s real snug.
One old set of tire chains I have fit both 265/75 and 255/85 tires similarly, I believe both tire sizes use the same chains. My chains are too small for 285s.
And of course I haven’t quite made up my mind re tire type either. The AT’s have done surprisingly well, but I find myself looking hard at the Toyo MT’s and Mickey Thompson MT’s. My son runs 33×12.50 Mickey Thompsons – and they’re terrific off-road, but I’m not that impressed with them on pavement.
When I finish telling the story of using the Toyo M/T on my F-350 the rapid wear might surprise a few readers. I’m a fan of Toyo tires, but when I can, I much prefer a tire that will offer less noise and longer wear. Of course tire wear is often specific to the platform, driver, and use.
There are a set of Mickey Thompson MTZ tires sitting in my shop mounted and ready for use on my Tundra, but have only seen about 2,000 miles of travel. I like them, but I’ve preferred the Dick Cepek FC-II treads I’ve been running for most of the Tundra’s miles. The FC-II (replaced by the Fun Country) has less noise, excellent siping, and have been slow to show wear on everything from an F-350 diesel, the Tundra, and a built V8 4Runner. Of course neither the Fun Country nor the Mickey Thompson MTZ tread are available in the 255/85R16 size.
The biggest decision you have to make is tire size. If you chose either a 265/75 or 285/75 your choices are many, both a blessing and a curse. If you decide to try a set of 255/85R16 rubber, then it will be relatively easy because the choices are relatively few.
If the 255 size wins, and you decide you don’t want a loud or faster wearing mud-terrain tire (Maxxis Bighorn, Toyo M/T, or BFG KM2), I’d suggest you consider a set of Cooper S/T MAXX. The S/T MAXX has only been manufactured in the 255/85R16 size since the first quarter of 2014. I’m currently running a set in the 255/80R17 size on my 4Runner.
Several weeks ago I posted about purchasing a set of OE 17-inch TRD wheels which included the original BF Goodrich All-Terrain 285/70R17 tires (17″ Tundra Wheels & BFG A/T Tires). However those were not the first, nor the best, set of TRD Rock Warrior wheels I have purchased. The Cooper S/T MAXX trial started last summer and has drug on for a while.
The reasons for buying the 18-inch Tundra SR5 wheels was because I wasn’t enthralled with the fake beadlock rings on the Rock Warrior wheels (Goodbye Bling Rings), and because finding a set of 17-inch TRD second generation Tundra wheels for a reasonable price seemed nearly impossible. Most of the sets on Craig’s List were almost new, with almost new tires, and guys wanted almost new prices, upwards of $1,500 for the tires and wheels. No thanks. In addition to being far more than I was willing to spend, because I’m not a BFG A/T fan (not a hater, just not a fan) I really didn’t want to pay anything for BFG A/T take-off tires.
There were two issues with the 18-inch Cooper S/T MAXXs: the drifting to the right, and the stiff ride from the rugged, short sidewalls. I could seek alignment solutions for the pulling—which I doubted would work—but how could I soften the ride of the stiff, short sidewall tires without letting too much air out? The stout construction of the S/T MAXX appeals to me, there is a time and application for these tires and I wanted a set, but the 18-inch 275s were rougher that I cared to drive on.
After deciding I wasn’t going to keep the 275/70R18s, and to take advantage of Discount Tire’s excellent exchange policy, the question was exchange them for what? Another set of F-C II? That seemed a bit silly, since my existing set was almost new, and I’d rather have one set of mild treads and another more aggressive. Though I knew a second set of F-C II wasn’t going to pull to the right and wouldn’t be a waste of money. Since I’d been down this road several times with the 4Runner, I was confident I knew the unhappy ending.
The First Set of TRD 17-Inch Rock Warrior Wheels
Knowing my dissatisfaction with the 18-inch sidewalls, early one morning my friend Frank inquired about finding a second set of 17-inch TRD wheels. I quickly dismissed his idea, telling him via email I had looked and they were all too expensive… But I decided to look again, and hidden among all the ridiculously expensive was one reasonably priced set at an independent tire dealer in Sacramento, just a couple hours away (thank you Frank). I was the first person to contact the seller, told him I’d be there in a couple hours if he would hold them for me.
Though there was summer road construction in the Sierras, and the several thousand vertical feet lost and gained during the 228 miles of travel, careful use of my right foot allowed the Tundra to squeeze 17.88 miles from each gallon.
The wheels were not perfect, but in hindsight they are the best set I’ve purchased thus far. There were a few scuffs on the fake beak lock rings from careless handling (which helped me to negotiate a lower price), and three of four spring clips that secure the center caps were missing, which I didn’t notice until I was home. But overall they were a very nice set the will likely stay with the Tundra as long as it lives in my barn.
With another set of 17s in the shop I didn’t know what I was going to exchange the S/T MAXX for, but I knew they were not going to be 18-inch tires.
All thirty-threes are not created equal, because they’re not all exactly thirty-three inches tall. The very common 285s are typically 32.8-inches tall while 255/85R16s are almost always 33.3+ inches; the Toyo M/T is 33.5-inches! Removing the Dick Cepek F-C II 17-inch 285s, slapping-on the 18-inch Cooper S/T MAXXs, and taking a few measurements showed that the taller 275/70R18 MAXXs were good for 3/16″ of additional clearance under the rear differential. Nice.
My initial S/T MAXX drive was on a test loop I typically travel after any tire, wheel, air pressure, alignment, or other drivability changes are implemented. It’s several miles long and includes city streets, rural highway, interstate freeway, and sometimes just a minuscule amount of dirt for photos. The route and terrain are familiar, as is the vehicle platform, what’s being evaluated is the change, in this case, tires.
What noise? Articulating tire noise can be a challenge, as vehicles have different levels of insulation and sound deadening, and drivers have their biases and tolerance or lack thereof for noise. With several back-to-back tire tests under my belt the S/T MAXX is clearly one of the quietest traction tires I’ve ever had the pleasure to drive on. The volume and tone is similar to my beloved Dick Cepek F-C II, but a bit quieter, and the MAXX is certainly quieter than the standard Cooper S/T. Comparing the S/T MAXX to the super popular BF Goodrich A/T is tough. While I currently have a set of used BFG A/Ts, I have few personal miles on them and I’m not a BFG A/T fan. I’ll go out on a strong limb and say the new S/T MAXXs are louder than the BFG A/T, but not much. For a tire that offers as much traction and void (much more than the BF Goodrich A/T) the Cooper S/T MAXX is an amazingly quiet tire and well worth the little noise it makes.
As noted in my introduction, the ArmorTek3® carcass construction and 3-ply sidewalls of the S/T MAXX are stiff. This can be great if this is a feature you are looking for, or a negative if you prefer a more compliant ride and/or a lighter tire. (If you are new to this blog or subject, read Wheels, Tires, and Sidewalls from Jan. 30, 2012.) In addition to the intentionally rugged design of the S/T MAXX, using 18-inch wheels with only a 33-inch tire adds to the lack of sidewall flex.
One of my strong dislikes for tall wheels on light-trucks is manifested by this situation: a relatively tall tire (33+), with a relatively short sidewall doesn’t offer the same off-highway flex and performance available from a taller sidewall. The same height tire on a 16-inch rim would yield an additional inch of sidewall to drive and flex on; this is not a small difference. If you already use and like the firmness of a load-range E sidewalls then the stiffness of the S/T MAXX (similar to the Toyo M/T) may not bother you, particularly if you don’t have to run it on a tall wheel. However, if you prefer a more compliant ride or a lighter tire you might reconsider the MAXX. What do you want, and what do you need for your application?
Pulling To The Right
Several years ago I rarely experienced tire pull problems with my trucks, however they are all live-axle 4WDs. Starting with my 2006 V8 4Runner and now continuing with this Tundra, I’ve experienced a pull (or drift) to the right with certain tires but not with others. Both of these IFS four-wheel-drives have alignment settings and geometry that are equal to or better than when new.
Aftermarket upper-control-arms are employed and expertly adjusted, though invariably some tires cause a very noticeable drift or pull to the right. I’ve spent countless hours and dollars to try and understand, identify, and combat this situation on these Toyota 4WDs. In short, my work involved many trial-and-error alignment adjustments, tire & wheels swaps, rotations, and tire pressure changes, all of which did not correct the problem. Some tires would still pull right, some terribly so.
How bad is the pull or drift? On a straight section of freeway with little road crown, at 65 miles-per-hour, releasing the steering wheel will result in crossing the right lane-line in about 3-seconds. Three seconds! I’m a strong advocate of keeping one, if not two hands on the wheel, and paying attention to the task at hand when driving. But I also like my vehicles to have very neutral handling, heading straight down the road unless instructed otherwise. Modified or not, I require my vehicles to drive almost perfectly on-highway. For comparison, depending on the road, wind, and other variables, with the same alignment settings Dick Cepek F-C II tires would continue straight for 8–10 seconds with no-hands.
Some readers may observe that the wheels are not identical. OE 17-inch forged TRD wheels are being used for the F-C II, while the MAXXs are mounted on 18-inch SR5 wheels, and there is probably a slight difference in backspacing. Is that part of the problem? I doubt it, though I did consider of this difference, and have a plan.
After an interlude, there will be more Cooper S/T MAXX commentary in the future—first we have to drive there.