Cooper Discoverer A/T3

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Testing & Talkin’ Tires

October 6, 2016

Even casual readers of this site will notice that I’m a light-truck tire aficionado; there are many posts about rubber for light-trucks. My personal obsession aside, there are powerful reasons tires are such a popular topic for both writers and enthusiasts nearly everywhere we gather. Mounting new meats is one of the easiest and most dramatic performance and/or appearance modifications owners can make to their trucks. Replacing worn rubber with new, even the same pattern, can greatly improve safety and traction. If you have any doubts, watch this Tire Rack video regarding tread depth and stopping distances on wet roads: tirerack.com/videos/index.jsp?video=5&tab=tires

Looking through a historical lens, modern tires are generally excellent, with unsurpassed designs and sizing options, and they are a good value. Yet value doesn’t mean inexpensive, and depending on the size and performance category, a new set of shoes for your truck can easily top $1000. This substantial outlay leads to questions and much research for many buyers.

Still Plays With TIRES means frequent trips to tire stores with a few shoes and insoles. This is a moderate load, sometimes I need a bigger trailer.

Still Plays With TIRES means frequent trips to tire stores with a few shoes and insoles. This is a moderate load, sometimes I need a bigger trailer.

Journalism’s Dirty Tire Secret

If you read truck tire reviews critically, you may realize that many involve very few miles of use before the evaluation is penned, often as little as a few hundred miles. Reasons for this include the long lead-time for print periodicals, editors’ desire to publish something as quickly as possible, and sometimes a little pressure from the manufacturer or advertising agency folks. Writers sometimes mount new tread and take them on a little excursion, writing much about the adventure and some about the tires, then use this one experience as the appetizer, main course, and dessert. Meh.

Another favorite is the manufacturer’s initial ride-and-drive test at a testing facility or track. When possible I happily attend and enjoy such events, but they are mostly a good introduction. If they’re not followed with a longer, personal-use test, they often don’t tell the complete story.

When one brand redesigned their super-popular all-terrain pattern two years ago, they hosted journalists in Baja where the test vehicles were race buggies and Ford Raptors. I have no doubt that the conditions and obstacles were gnarly, and I’m not saying the product isn’t good. But how does one test a tire’s performance on an unfamiliar chassis, particularly on a race buggy or (factory) desert-prerunner truck? Where is the baseline? Are the tires being tested, or is the complete chassis? Would these highly-capable vehicles perform impressively if another tire brand or design was mounted? Surely.

Hopefully readers can benefit from my continuous evaluations. Instead of buying a new set every few years like many consumers, some running the same or similar treads repeatedly, I typically test a few sets each year. My personal experience and database over the past two decades is quite large, and includes aggressive mud tires, tame all-terrains, and many in-between. Although I swap tread often, I dismount them from wheels infrequently. At any given time I have several sets of tires on OE wheels, currently six that fit my 2014 Ram 2500, and keep notes on the dates, miles, performance, and wear. Some I buy, and some are supplied by manufacturers for review. Just this week I sold two older sets, one Ram and one Toyota, and bought a new set for my 2500. Some get more miles than others, depending on my needs and preferences, the physical size or fit, and how well they mesh with current objectives, but all receive thousands not hundreds of miles. Several years ago a teasing friend dubbed me “the Imelda Marcos of tires.” What can I say, if the shoe fits….

Starting lineup. There are few truck parts (any?) I like more than a fresh set of rubber.

There are few truck parts (any?) I like more than a fresh set of rubber.

Cooper Discoverer A/T3

Over the past several years Cooper Tire and Rubber—which is still a U.S.-based company and manufacturer—revamped their light-truck line. The 5-rib all-terrain Cooper Discover A/T3 is a natural choice for someone wanting better traction in more varied conditions than a highway tire (HT) offers, but something quieter, smoother and softer than a commercial traction pattern like Cooper’s S/T MAXX (which I’ve run on my 4Runner for a few years). The performance improvement over an HT can be substantial in inclement weather, including something as common as a hard rain, but the differences can be even more dramatic with a little snow, slush, or ice covering the roadway.

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Because the A/T3 is their flagship all-terrain tire there are an impressive 56 sizes. The outer rib’s open lugs allow liquid and debris to escape better than highway designs, as do the circumferential voids in the center. The silica-based compound improves wet traction and on-highway handling, provides cut and chip resistance on rough terrain, and reduces rolling resistance. Lateral groove protectors reduce stone retention and drilling, and the broken center rib is designed to improve soft surface traction. It is M+S rated, and has a 55,000 mile tread wear warranty.

There will always be a place in my heart and space in my garage for high-void traction tires, though maturing has made me increasingly less fond of louder designs when they are not necessary. The A/T3 is pleasant, barely audible to my ears, and notably quieter than the similar but slightly higher-void 5-rib Toyo A/T II tested on my Ram for 8,000 miles. (The Toyos averaged 1/32 of wear for every 2,100 miles, with frequent rotations, and were removed to mount the A/T3s.)

Comparing Cooper’s high-void, 295/70R18E STT PRO mudder to the the 285/75R18E A/T3. Both sizes support 4,080# each at 80 psi.

Comparing Cooper’s high-void, 295/70R18E STT PRO mudder to the the 285/75R18E A/T3. Both sizes support 4,080# each at 80 psi.

Again I chose the fantastic, niche, LT285/75R18 size. Cooper is one of a handful of companies making this approximately 35×11.50 inch size, tall but not overly wide. These Coopers are 34.84-inches tall, with 17/32 of tread depth measuring 8.9-inches wide, and weighing 58.4-pounds solo and 90 when mated to Ram Big Horn WBJ forged aluminum wheels. They fit perfectly on the stock 8-inch wheels, and like any pattern in this size, will support a massive 4,080 pounds at 80 psi. Loaded to the Ram’s GVWR, with 60 psi in front and 80 psi in back, the rear differential ground clearance is 8 3/4 inches.

Balancing Act 

Using my favorite local Discount Tire store the Coopers were dynamically (dual-plane) balanced. As always Centramatics balancers work in the background, adjusting to any irregularities on-the-fly. The A/T3s took very little wheel weight to balance, and they have remained smooth at all speeds, legal and above.

Inside              Outside

#1 3.00            0.25

#2 1.75            1.75

#3 1.50            3.00

#4 1.25             3.00

The LT285/75R18E Discoverer A/T3 starts with 17/32” of tread.

The LT285/75R18E Discoverer A/T3 starts with 17/32 of tread.

Ride quality is smooth and compliant; the traditional construction 2-ply sidewall is not stiff, and helps absorb impacts, even at full pressure under a maximum load. The generous and squiggly shape of the siping helps grip, and is surely behind some of the excellent winter traction endorsements I’ve read on snow plowing sites (my A/T3s have not seen much wet yet). Straight-line tracking is good as one would expect from a 5-rib all-terrain/all-season design, as is steering response. When conditions are right my truck will drive straight for 10 seconds or more with no input. It’s too early to report on wear, but after the first 2,500 miles, it looks mileage will be similar to the Toyo A/T II tires mentioned above.

The A/T3 doesn’t feature or need sidewall tread for its target market.

The A/T3 doesn’t feature or need sidewall tread for its target market.

Supporting Documentation

Confidence in my prose is important, but I enjoy sharing others’ views when it helps make a point. Before accepting the Senior Editor post at OutdoorX4 magazine, I was a technical editor at Overland Journal (OJ) for a few years. For the Summer 2014 issue, OJ conducted a comprehensive, seven tread, all-terrain comparison which was later published online, and can be read at: expeditionportal.com/where-the-rubber-meets-the-road. The article is a good read for traction tire enthusiasts. The short version is that the Cooper Discoverer A/T3 won both the prizes given after these tests are completed: the “Value Award” and “Editor’s Choice”.

For a less analytical but impressive amateur review, this YouTube link gives a snapshot of the A/T3’s winter performance potential. A competitor’s design with plenty of tread remaining cannot start up a snowy incline in 2WD, but with Cooper A/T3s mounted, the truck moves forward.

youtube.com/watch?v=m2OHErN5ZOI&app=desktop

If you are in the market for a traditional 5-rib all-terrain, but with an updated design and reputation for superior traction, consider the Cooper Discoverer A/T3.

Sources:

Cooper Tires: coopertire.com, 800-854-6288

A version of this article was published in Issue 93 of the Turbo Diesel Register magazinein my Still Plays With Trucks column.

Copyright James Langan/RoadTraveler.net