Cooper S/T MAXX LT275/70R18E Preview (Traction Tire Part 2)

The Cooper S/T MAXX 

After deciding the LT275/70R18 was my perfect 33-inch tire for an 18-inch wheel, and seeing there is a nice selection of tires in this size, a tread had to be chosen. This was relatively easy as I’m familiar with most of the popular light-truck traction tires. I’m a fan of Cooper Tires and their subsidiaries, and the new S/T MAXX design was already on my to try list, offering the type of any-terrain tire I prefer—not too biased toward on or off-highway. Cooper calls this a 50/50 tire (on/off pavement) and I’d say they are very close to hitting that mark.

LT275/70R18E Cooper S/T MAXX

After some online shopping, my local Discount Tire matched a price from TireCrawler, a mere $242 each delivered. (This was a few months ago; tire prices change, usually increasing.) Discount ordered the tires and a few days later I hauled my 18-inch wheels to their shop for mounting and balancing. Cooper says the LT275/70R18E MAXXs are 33.35 x 11.2 inches and my scale said they weigh 60.5-pounds each. Combined with the relatively heavy, 30-pound, 18-inch cast aluminum SR5 Tundra rims, each tire/wheel combo weighed 91-pounds!

Stout Construction

Once you get your hands on one, there will be no doubt the S/T MAXX is a super stout tire. The scale tells part of the story, though not all load-range E or 3-ply sidewall tires are created equal (see Wheels, Tires, and Sidewalls). Grab an unmounted ArmorTek3® sidewall and give it a good jerk back and forth, they’re stiff, similar the Toyo MT, and more substantial than the 3-ply sidewalls on the very common BFG All-Terrain. The MAXX sidewalls are much stiffer than the older and lighter-duty Cooper S/T, which offers flexible sidewalls and very little sidewall tread. Similar name, and I like both treads depending on the intended application, but they are very different tires. Try not to confuse the S/T MAXX with the S/T, or the Cooper STT… maybe Cooper needs some new letters?

The S/T MAXX has beefy sidewall lugs/tread.

The S/T MAXX is an impressive looking tire. The sidewall lugs are attractive and thick, more impressive in person than in the photos I’d seen, and possibly the most aggressive sidewalls I’ve seen on a tire in this class (not a mud-terrain). The tread is a hybrid 4–5 rib design with a bit less void than the older 4-rib S/T, the center circumferential groove is noticeably missing. There is a moderate amount of siping and the cut & chip resistant compound is studdable. Cooper describes the MAXX as a “commercial grade traction tire”, an accurate description.

S/T MAXX 4-5 rib hybrid tread design.

Mount & Balance 

Mounting a 275/70R18 S/T MAXX on Tundra 18 inch SR5 aluminum wheel.

Mounting the first tire and giving it a spin on the balancer showed it wanted 3.25-oz. inside and 4.75-oz. outside for a dynamic balance. Eight ounces is not much weight for a 91-pound spinning mass, but I generally like to add less weight to my wheels when possible.

While dynamic balancing is the technically the best as it balances in two planes, I’ve had many positive experiences using the single plane static balance method for heavy RV tires (an old term). Static spin balancing counters vertical imbalance (hop) of a tire & wheel, and I don’t run very wide tires where dynamic balancing can be more important. Generally, I see how the first couple tires in a set balance and if they can be dynamically balanced with moderate weight, that’s what we do. If they are going to ask for substantial weight using the dynamic method, I choose static.

Modern balancing machines are very good.

Sometimes this difference can be very dramatic. A few months ago a heavy, high-quality tire wanted about 9 ounces for a dynamic balance, but only 1.5 ounces for a static balance. Guess which one I chose? The S/T MAXXs were single pane balanced and the road force (RF) was also measured—which was very low—another indication of quality. For more thoughts on tire balancing you can read Static Balance Details.

Static Balance Numbers

#1) 4.75-oz. RF .002″.

After seeing this low road force number the kid doing the balancing commented “Wow, that’s like a Michelin.”

#2) 4.25-oz. RF .008″

#3) 5.50-oz. RF .007″

#4) 1.50-oz. RF .009″

Cooper Tires’ website lists the tread depth for every S/T MAXX currently made as 18.5/32″, which it probably is. But it would be pretty easy to call this 19/32″ as measuring down to one-sixty-fourth can be a challenge. The original tread depth is important, more is better for most truck tires, though the long-term wear rate is also important. Combine deep tread with a low rate of wear and you have a long-lasting tire.

LT275/70R18E COOPER S/T MAXX tread depth.

Because my original 17-inch Tundra TRD wheels use tapered lug nuts, which are uncommon for modern Toyota trucks, I needed new shank-style nuts for the 18-inch wheels. Searching online I found a source for the Gorilla brand lug nuts and locks, a complete set was delivered for about $110. I’ve been using an impact-gun on Gorilla wheel locks on my 4Runner for years, and they have held up to my intense use. I wish they would fit on the OE 17-inch TRD Tundra wheels.

Shank style Gorilla locking lug nuts needed for SR5 wheels.

Driving Impressions

To be continued…

Copyright © 2012 James Langan


6 thoughts on “Cooper S/T MAXX LT275/70R18E Preview (Traction Tire Part 2)

  1. After putting 10,000 miles on the ST Maxxs mounted on my Tundra it’s safe to say these are my new favorite tire. Their quiet and well mannered on the road, handle the clay, mud, and shale tailings that make up the backwoods trail in our area with ease and are surprisingly great on icy and slippery roads. Dare I say that they are as good in the snow as my old favorite the Dick Cepek Fun Country IIs? Yes I do. I’ve been really impressed with the winter traction on these tires over the winter months though due to a warm winter and little accumulated snow pack I didn’t get to see how they do in deep snow.. Like James I found I had to play with tire pressure to achieve a good contact patch on the Maxxs’ (less than the former tires on the truck) and my mileage did take a 1 mph hit even though the Maxxs are the same size as the previous tires. I’m diggin’ these treads. But that being said when it comes time to put new tires on my ’04 Jeep Unlimited I’m going to mount up a set of FC IIs. Why? Because you can feel the weight of these tires on how the vehicle preforms and I don’t think they are a good match for a marginally powered vehicle. So I’ll give up some mud performance for increased seat of the pants power and gas mileage by using the DC IIs over the Maxxs.

  2. I’ll take a stab at this and you’ll say: “After finding the proper inflation amount to run an E rated tire, these tires ride very nice albeit a bit more firm the the old ST, but still comfortable nonetheless. I do notice, after having many sets of similar and more aggressive tires, that the Coopers are very quiet – quieter than their ST forebearer – maybe not quite as noiseless as a BFG AT, but very quiet for all the lugginess of the tread. I am also saddened by the 1.5 mpg loss the Tundra has taken since installing these, but, oh well, it is a brick of a truck afterall.”

    How close am I?

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  4. Interesting design similarities to the Duratrac tire: large outer lugs a la the M/T style and a grouping of inner A/T style lugs. Cooper has 3 inner lugs and the Duratrac has 6 smaller ones. The Duratrac seems to have more siping overall. Hurry up and write your driving impressions installment!

  5. They look like nice tires. I considered them before I purchased my Cooper STTs. I love my STTs but I wish I could get them or the ST MAXX in a 255/85R16. The 285/75R16s I have now are the first over sized tires I’ve ever put on a vehicle. They perform well but I sometimes wish they were narrower. I’d love to see a major pickup line decide to use a 255/80R17 or something like that to breath new life into the tall and skinny tire. But since the latest trends are big 20″ rims that probably wont happen. How do you like the 18″ rims. I could move up to a 17″ rim but 18″ just seems like too much rim for a Jeep. Please post some pictures of your vehicle with the tires mounted. I’m anxious to see what it looks like.

    By the way, nice blog. I’ve viewed it before but I’ve never signed up. But I just did now.

    • Great comments and questions Fargo… almost warrants another blog post but I’ll answer and comment here. Thanks for signing up for the blog, more and regular readers will help sustain this blog/site in the long run. Tell a friend about RoadTraveler.net 🙂

      Q. “I’d love to see a major pickup line decide to use a 255/80R17 or something like that to breath new life into the tall and skinny tire. But since the latest trends are big 20″ rims that probably wont happen.”

      A. You hit the bullseye with this statement, exactly my sentiments. If there were at least a couple 255/80R17 treads to choose from I’d have set in my garage right now instead of only 285s. Unfortunately BF Goodrich is the only company making a 255/80R17 tire, and only in the KM2 mud-terrain tread. I’m confident I could pickup 1–2 MPG on the highway with a 255/80 over a 285, which has been my experience with 16-inch 255s.

      I’ve considered tying a set of 235/80R17 tires, but don’t want to run a one inch shorter tire and loose one-half-inch of ground clearance in the process. Because the LT235/80R17E is a popular replacement for the once universal heavy-duty light-truck 16-inch tire, the LT235/85R16E, there are many 235/80 choices. I agree, if an OEM was to spec the 255/80R17 on a new truck we would have replacement tires available in this size.

      Q. “How do you like the 18″ rims. I could move up to a 17″ rim but 18″ just seems like too much rim for a Jeep. Please post some pictures of your vehicle with the tires mounted. I’m anxious to see what it looks like.”

      A. I don’t like tall wheels. If you haven’t read my recent post about wheels, tires, and sidewalls, take a look and my biases will be clear. These 18-inch rims were purchased and used because they were the first set of inexpensive OE wheels I found on Craig’s List. I didn’t think I was going to be able to find a set of reasonably priced OE 17-inch TRD wheels for the Tundra, but I was incorrect and later found and purchased a couple sets. Pictures with the tires mounted will be in the next post.

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