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Massive Mud Tire Shootout: Intro

Posted in How To: Wheels Tires on April 1, 2011 Comment (0)
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Photographers: Cody Kanuscak

Mud tires are about as varied as the flavor combinations at a big-chain coffee shop. However, unlike the jittery effects of triple-strength latté, a good mud tire will return ample traction where it matters most, and then transition smoothly to the next task you throw at it. A tire's ability to propel a vehicle in deep mud boils down to three key factors: tread and sidewall design, carcass flexibility, and compound. Each of these factors can have good or bad effects on a tire's performance in other types of terrain. What might be awesome in deep gooey mud might be absolutely a nightmare on the street, and vice versa. We believe a good mud-terrain tire should perform well in all versions of terra firma; after all, mud only happens when dirt and water mix. The rest of the time, you have dirt, rock, sand, and snow-not to mention all forms of pavement.

With this test, we set out to evaluate ten popular mud tires in an assortment of real-world driving scenarios. The idea was to mimic what the average 4x4 enthusiast, who drives his or her vehicle daily, might encounter in any given month. We wanted to see how each of the three variables listed above affect total tire performance. We picked a 37x12.50R17 because it is one of the most popular sizes used on lifted vehicles today. As such, our results are not geared towards competitive mud boggers, or trailer queens that rarely touch the pavement. We set up this shootout for the average wheeler who, like us, uses his or her primary vehicle for all aspects of life, from navigating backcountry trails to retrieving a cup of Joe at the local strip mall. With that in mind, the rankings on the pages that follow should be considered in terms of the tires' overall performance, both on- and off-pavement, and not solely construed to performance in mud. Also, we realize that there are many different types of mud around the country, so our impressions are based only on the kind of mud we encountered at our northern California test facility. As the old saying goes, your mileage (and your mud) may vary.

The Testing
To conduct an apples-to-apples comparison on 10 different tire brands, we needed to eliminate any potential for variables. First, we weighed each tire to ensure against manufacturing anomalies. We wanted to see how close each tire was to the manufacturer's published weight specification. This process was eye-opening, to say the least. Some were precisely in spec, while others were as much as 11 pounds over the published weight. Next, we secured 40 identical Classic II 17x9-inch aluminum wheels from Mickey Thompson. We had each wheel balanced without tires attached to ensure that any manufacturing variances would not affect our tire balancing results. We enlisted the help of the professionals at America's Tire in Salinas, California, to make this happen. As timing would have it, the folks at America's Tire had their monthly calibration service performed on the morning our tires and wheels arrived. We think balance-ability is a key factor of a quality tire, especially when you are talking about large and heavy mud tires. Achieving perfect balance is critical to the life of drivetrain components such as bearings, seals and the tires themselves. The better a tire is from the start, the easier it is to balance, and the more likely it will remain in balance while in use. Balance also says a lot about a tire manufacturer's ability to build a consistent product-something all tire companies strive for.

Once all tires and wheels were mounted and balanced, we took them back to our Northern California evaluation lab to conduct a barrage of assessments. We filled each tire to 35 psi and measured the static ride height. We were surprised to find that just one brand, Goodyear, measured over 37 inches tall. All others were just under the 37-inch mark.

Next, we lowered each set of tires to 10 psi and mounted them, one set at a time, to our JK test mule. We parked the Jeep on top of a 20-foot flatbed gooseneck trailer that we modified to quantify each tire's interface with the ground.

Our good friends at Mickey Thompson supplied 40 of their rugged 17 x 9-inch Classic II aluminum wheels for our testing. We like this wheel because it has a strong design with little opportunity for manufacturing variances. A simply designed wheel like this also makes it much easier to ensure that the balance of each wheel is perfect prior to mounting a tire.

To achieve this, we ordered a 24x18-inch piece of bullet-resistant acrylic glass from Tap Plastics in Stockton, California. We surrounded the 11/4-inch-thick acrylic sheet with a TIG-welded stainless-steel frame to help stiffen it under the load of the vehicle. We cut a hole in the wooden deck of the trailer and positioned the glass flush with the deck surface. This would allow us the opportunity to see what the ground sees when the weight of the vehicle is upon it. We took pictures of each tread pattern from below and, using sheets of white paper, isolated the part of each tread pattern that actually touched the glass. We found that every contact patch had a slightly different shape. We took measurements of each tire's footprint and calculated the total footprint area in square inches.

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With our footprint data tabulated, we taped off each tire's contact patch on a new un-mounted fifth tire of each set. Then, we measured out precisely how many biting edges each tread pattern had in its given footprint. We did this using a Scale Master digital plan measuring tool, which is essentially a digital ruler with a little rolling wheel that counts as you move it across a surface. We traced the contour of any tread element in the pattern that touched the glass and featured a biting edge. These included the edges of individual lugs, as well as each side of any type of sipe or tread opening.

Finding the biting edges of a tread pattern is a tedious process that requires patience and a steady hand.

Next, we checked the hardness of the compound of each tire using a digital Shore type A durometer gauge tool. This information would tell us how much a specific compound would conform to a given surface. We took measurements in two areas of each tire: the tread and sidewall.

With all the data tabulated, we started the drawn-out road test process. Our route consisted of 100 miles that would provide critical feedback on each set of tires. The loop included rural paved roads, multi-lane asphalt and concrete freeways as well as a few miles of twisty dirt and gravel. We checked each tread's noise level using two individual decibel meters to produce an average sound level per pattern.

This is a look at what the ground sees when a tire is aired down to 10 psi.

Finally, we loaded the pressure washer, floor jack, and air compressor along with all 40 tires in a 16-foot dump trailer and headed out to Hollister Hills SVRA for a day of back-to-back mud-terrain testing. Luckily, the day we did our testing, it was raining all day long. This gave us the opportunity to evaluate each design over a test loop that would easily find the limits of each tread's ability to make traction. The area we used for this testing featured parts of the area we use for the Obstacle Course at Top Truck Challenge. We drove each set of tires up and down the rain-soaked Truck Hill hillclimb, as well as through a two-mile loop featuring one very challenging, rutted off-camber S-turn hill climb with slippery clay mud.

At the end of our mud testing, three tread patterns in particular seemed to overshadow the others. However, as we stated earlier, we believe a mud tire should perform well in all types of terrain. So we had to also consider the data acquired during our 100-mile on-road testing, too. In the end, even we were surprised with the results.

The Tires
(in alphabetical order)
BFGoodrich Mud-Terrain T/A KM2
Goodyear Wrangler MT/R with Kevlar
Hankook Dynapro MT
Maxxis M8060 Trepador
Mickey Thompson Baja MTZ
Nitto Trail Grappler M/T
Pit Bull Rocker LT
Pro Comp Xtreme Mud Terrain
Interco Super Swamper TrXus
Yokohama Geolandar M/T

Compound Durometer
Tread Sidewall
BFGoodrich Mud-Terrain T/A KM2 66 58.5
Goodyear Wrangler MT/R with Kevlar 71 67
Hankook Dynapro MT 63.5 61
Maxxis M8060 Trepador 72 61
Mickey Thompson Baja MTZ 65 55
Nitto Trail Grappler M/T 66 52.5
Pit Bull Rocker LT 58 60
Pro Comp Xtreme Mud Terrain 66 61.5
Super Swamper TrXus 64.5 55
Yokohama Geolandar MT 69 65

More About America's Tire
Discount Tire and America's Tire are two unique names for one nationwide company. Discount Tire started in Michigan in 1960 and has since spread its wings from coast to coast, with over 600 retail stores. However, in some regions, other companies already held the name "Discount" in a similar context. In those regions, the name America's Tire was adopted, and any purchase made at any Discount Tire or America's Tire store can be serviced at locations bearing either name. For over 28 years, Discount Tire/America's Tire has offered a very customer-friendly tire replacement program the company refers to as the Certificate for Refund, Repair or Replacement program. Unlike most tire warranty programs, if a tire purchased from Discount or America's Tire should fail due to a defect or an non-repairable road hazard, still has legal tread (3/32 inch) remaining across the tire, and is less than three years old, Discount Tire/America's Tire will give a full refund of the purchase price. They will even give you the option to purchase the same new or comparable tire at the refund price. There is no prorating, no disqualification for any reason, and no mileage adjustment. We think it's the most comprehensive tire certificate program available today. Info: America's Tire, 800/589-6789, www.discounttire.com

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