Testing Cooper® Discoverer AT3 XLT™ Tires

For an accurate test of the Cooper Discoverer AT3 XLT tires, our first step was precision mounting and balancing of the tires. (See the Part 1 video above.) In the Part 2 video, we prepare the Ram 3500 for testing then test the Cooper Discoverer AT3 XLT tires both on- and off-road. Part 2 video concludes with a performance evaluation of these 37″x12.50R17 Discoverer AT3 XLT tires!

Cooper® history dates to 1914, a legacy straight from the heartland of the American tire industry. Cooper Tires® pride in quality and the company’s commitment to safety are hallmarks in today’s tires. The Discoverer AT3 XLT™ features (described in the Part 1 video above) include high marks for longevity and hauling ability.

These latest Discoverer AT3 XLT™ tires from Cooper® boast exceptional wear resistance and a rugged design. In our two-part HD video coverage, we begin with mounting and balancing a set of 37″x12.50R17LT AT3 XLT™ tires on the magazine’s Ram 3500 4×4 pickup. These Load Range D tires rate 3,525-pound capacity per tire and engineering aimed at longevity. The Part 1 video coverage also includes an overview of the Cooper Tires® Discoverer AT3 XLT™ technology and design features.

The 18/32″ tread depth contributes to the long service expectations. In addition to a “Standard Limited Warranty” and a “Free 45-Day Road Test”, Cooper® offers “60,000 Mile Treadwear Protection” on the LT-metric size Discoverer AT3 XLT™ tires. (See the Cooper® website at http://us.coopertire.com/ for more details.) Intensive Cooper® research and testing contribute to these terms.

Tires balanced to industry standards by Discount Tire at Los Altos Parkway, Sparks, Nevada, we began our testing of the Cooper® Discoverer AT3 XLT™ tires. In the Part 2 video coverage (below), see our test findings and an in-depth look at how we assure accuracy during our tire tests. The 37″x12.50R17 Cooper Discoverer AT3 XLT™ tires delivered optimal performance and mileage under these conditions.

Part Two: Accurately Testing the AT3 XLT™ Tires

We road test only after close attention to mounting, balancing and wheel alignment. This is the only way to accurately compare tires. In 2021, we brought tire changing and balancing into our shop to provide the highest degree of accuracy for testing tires. We also perform our own wheel alignment in-house and check alignment before each tire test.

When we test tires, the vehicle’s suspension, steering system, wheel alignment and tire pressures are under constant scrutiny. Consistent, well planned driving environments make our comparisons fair. The result is an objective look at the tires’ performance and wear characteristics.

Note: As a general rule, if the test vehicle’s condition or the testing methods fall short, a tire test is unreliable. Consumer reviews can fall into this category, too, especially comments about disappointing mileage. The Part 2 video provides insight into how you can maximize tire performance and lifespan.

Every tire test should begin with a thorough check of the vehicle’s suspension, steering system, brakes and wheel alignment. Consistency, repeatability and fair testing require a sound vehicle.

Our tire tests begin with a full chassis and wheel alignment check. At each tire rotation, we repeat the procedure. Here, we level the Ram truck to make a front suspension, steering and wheel alignment check. The Cooper Discoverer AT3 XLT™ tires have accrued 5,200 miles, and they are due for the first rotation.

The frame has a known “level” area for checking the vehicle’s angle. This must be done before performing each wheel alignment check. Frame angle affects caster angle. An accurate caster check requires a level frame.

We begin the alignment check with camber angle. The gauge reads 1/4-degree positive camber, the optimal setting for the 2005 Dodge Ram 3500 beam front 4×4 axle. Actual readings were between 0.25-degrees positive and 0-degrees camber, still within specification. In fact, the AAM front axle has surprisingly true camber and caster angles from the factory. Normal steering knuckle upper ball joint wear can often tilt the wheel slightly negative.

When the 4″ Mopar® chassis lift went into place seven years ago, the caster angle was reset to the factory 4.5-degrees positive caster. This adjustment has held the entire time, a tribute to the quality of the suspension components and a few minor upgrades applied during the kit’s installation.

Toe-in is easily performed with two Specialty Products Company (SPC) FasTrax® gauges, a pair of Gil Smith Racing Fabrication turn plates and a quality tape measure. Taking time and care to set up the equipment properly, accurate alignments are possible at a smaller shop or the DIY level. The floor must be flat, and the portable plates require proper positioning. See details in the Part 2 HD video coverage.

Our 2005 Dodge Ram 3500 4×4 Quad-Cab now has 177K miles on the odometer. Bought new, the truck benefits from a rigid preventive maintenance schedule. The Cummins turbo-diesel places weight bias to the front when the truck is unloaded. Trailering with a load distribution hitch levels out the weight per axle. Tire pressure, always checked cold and in the shade, is continually checked and adjusted for load, terrain and the climate.

Our 2005 Ram 3500 4×4 has been an optimal testbed for tire testing. Consistent chassis measurements produce accurate and reliable results. We always verify the chassis and suspension condition before starting a tire test. Under these conditions, the Cooper Discoverer AT3 XLT™ 37″x12.50R17 tires were thoroughly tested and evaluated . (See the Part 2 video for details.)

We always maximize the mileage from our tires, and Cooper’s Durable-Tread Technology® assures that these tires will perform safely for a long time. In our tests, these tires delivered. Long mileage will make the Discoverer AT3 XLT™ tires popular.

Whatever your tire needs or tread preference, before mounting new tires, consider the condition of your truck. To maximize mileage and get the best performance from new tires, consider our approach. At 177K miles, the Ram delivers optimal performance. Preventive maintenance also enhances the tire mileage. Taking care of the chassis consistently returns high mileage from our tires. Make sure your truck performs at this level.

*Cooper Tires offers a range of “AT3” tires. Our test focused on the XLT. Shown here is the Discoverer AT3 4S. As of 2021, Cooper Tires became a subsidiary of Goodyear.*

The XLT is at left, the AT3 4S center and the AT3LT at right. Our test focus is the AT3 XLT in a 37×12.5×17 size. Large profile tires like this are weighty and a supreme test. On our Raceline wheels, the per tire/wheel weight is 102 pounds apiece.

A coveted SEMA Award acknowledges Cooper Tires®. At the leading edge of tire development, committed to customer satisfaction, the company and its products have earned these accolades.

37x12.50R17 4WD Mechanix Magazine AT3 XLT balancing tires beam axle camber caster Cooper Tires Coopertires Discount Tire Discoverer DIY Durable-Tread FasTrax HD video how-to product evaluation product test Ram 3500 steering linkage tire test toe-in video wheel alignment

Part Two: Accurately Testing the AT3 XLT™ Tires

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