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From Concept To Trail: Tire Basics

Posted in How To: Wheels Tires on April 1, 2012 Comment (0)
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From Concept To Trail: Tire Basics

Tires are a lot like shoes. Any shoe will protect your foot but there are specific shoes for specific activities. What works well in one activity may not work so well in another. For example, a basketball shoe works really well on the court, but not so hot on a hiking trail. A hiking shoe works great in the trail environment, but doesn’t cut it on the court. Similarly, the same is true for tires. Any tire will allow your 4x4 to roll, but there are specific tires for specific types of terrain and there are compromises with each. Here’s the thing: Shoes are relatively inexpensive so it’s feasible to have several different types on hand to match whatever activity presents itself. Tires, on the other hand, are not inexpensive. This means you have to get it right the first time. To do that, you need to purchase tires that help maximize your rigs performance in the type of terrain you most often travel. The best way to do that is to understand basic tire construction and the basic features of a specific class of tire.

The Basics
There’s a lot that goes into a tire before it actually goes into production. Cooper Tire, maker of the familiar Discoverer tire, follows this procedure: 1.) Marketing concept development. 2.) Product development. 3.) Mold development and procurement. 4.) Prototype procurement. 5.) Prototype testing. 6.) Design certification. 7.) Manufacturing.

The process of manufacturing a tire is actually quite complicated. Most tire manufacturers have an in-house technical center staffed by knowledgeable professionals armed with the latest technology. An example is this Cooper Tire engineer performing tests on a virtual tire using Cooper’s Virtual Tire Technology.

We’d love to show you the step-by-step process of how a tire is assembled, but almost every tire manufacturer restricts access to the actual tire construction process. This is because the tire business is very competitive and many of the processes and machines are proprietary. Basically, most radial tires consist of the inner liner, beads, body plies, antichafing strips, steel belts, tread, and sidewall. Most tire companies have technical centers where the staff can consist of mechanical and chemical engineers, chemists, physicists, and engineers. Among other things, these facilities are often where testing of the raw tire materials take place. During a tour of the Cooper Tire Technical Center in Findlay, Ohio, we saw its 7,500-square-foot materials laboratory where some of the machinery included a unit that is used to test rubber pellets. It could heat them, freeze them, and squash them to determine durability. Cooper has the ability to design, test, and evaluate tires on a computer. Of course, real world testing is mandatory, and for that Cooper has a sprawling 1,000-acre test center in Pearsall, Texas, which is home to a variety of asphalt tracks as well as numerous off-road courses. Point is, there’s a lot of technology and testing that goes into a tire before it gets the green light for mass production.

Automation is used throughout the tire-building and finishing processes, but as we learned during our tour of Cooper Tire, each finished tire is visually and physically inspected to make sure the tire is in perfect condition for the consumer.

Quite simply, in the 4x4 world you can break tire styles down into three major classes: all-season, all-terrain, and mud-terrain. Each of those classes contains a significant number of variations. The all-season class offers tires that specialize in snow and ice, for example. The all-terrain class is loaded with different tread designs of varying aggressiveness. Similarly, the mud-terrain class includes everything from somewhat mild tread designs to wildly aggressive purpose-built tires.

All-season
It’s no secret that the average 4x4 spends the majority of its time on the pavement. This means that quiet operation and wet weather and snow performance rank high on the list of desirable features for these tires. Typically they have a mild tread pattern with small voids between the tread blocks to decrease noise and improve steering response. These tires will also have lots of siping to funnel water out of the tread blocks and offer increased grip on ice. Internal construction often varies by size and load rating. The downside to these tires is that the mild tread pattern means they slip more than they grab onto typical trail obstacles like rocks and dirt; most sidewalls aren’t designed for off-road travel so they’re susceptible to punctures; the soft tread can chunk in rocky terrain; and because they aren’t designed for it, they tend to load up in the mud. On-road, they’re the king, offering near-silent noise emissions, incredibly grippy performance, a smooth ride, low rolling resistance (which will help your vehicle’s fuel efficiency), and long wear characteristics. Off-road their construction helps to contribute to a smooth ride and they typically perform well in sand and snow when aired down.

All-season tires, like the BFGoodrich Long Trail T/A Tour shown here on a Toyota RAV4 at BFG’s Laurens Proving Ground in South Carolina, are built to excel in day-to-day driving. This tire features staggered tread blocks for quiet operation and circumferential grooves in the tread, along with tread block siping, which funnel water so the rubber stays in contact with the road.

Some of the tires in the all-season category include:
BFGoodrich Radial Long Trail Tour T/A
Cooper Discoverer H/T
Falken Landair H/T
General Grabber HTS
Goodyear Wrangler ST
Nitto Dura Grappler
Yokohama Geolandar H/T-S

All-terrain
Like the all-season tire, the all-terrain will typically have siping in the tread blocks to enhance wet weather and ice traction. Some even utilize technologies from the all-season class like the Cooper Discoverer A/T3, which has a silica-based tread compound to enhance wet weather traction. All-terrain tread blocks will typically have larger voids than an all-season tire to enhance self cleaning. All-terrain tires run the gamut of tread aggressiveness, but most are designed to be quiet and street-friendly while offering increased capability off-road. Most all-terrain tires will offer decent tread life, good on-road handling characteristics, and increased load carrying capacity. Some all-terrain tires are blurring the line between an all-terrain and a mud-terrain, offering all-terrain-like on-road handling and manners but mud-terrain-like off-road performance due to larger, more aggressive tread and even aggressive self-cleaning side lugs designed to improve traction. The Dick Cepek F-C II is an example of this, and it’s actually built using a mud tire carcass. In addition to side lugs, some all-terrain tires have features that reduce the chance of stone retention, reduce the chance of sidewall punctures and tears, and protect the rim. Manufacturers often have their own trade names for these design features.

An all-terrain tire, like the Cooper Discoverer A/T3 shown here, is designed to shed mud better than an all-season tire. Some all-terrain tires are more proficient than others at this task. The way to find out how a tire performs at a given task is to read reviews like those in the “4x4 Tire Guide” beginning on page 36 in this issue.

Some examples of all-terrain tires include:
BFGoodrich All-Terrain T/A
Cooper Discoverer A/T3
Dick Cepek Radial F-C II
Falken WildPeak A/T
General Grabber AT2
Goodyear Duratrac
Mickey Thompson Baja ATZ Radial
Nitto Terra Grappler
Pit Bull Growler
Pro Comp Extreme A/T
Toyo Open Country A/T
Yokohama Geolandar A/T-S

Mud-terrain
Mud is an off-road staple worldwide and it takes a special tire to conquer it. Mud-terrain tires almost always have large lugs with more space between them than an all-terrain tire. These tires are designed to self-clean when spun, which gives them a clean bite into the goo at each rotation. Like some all-terrain tires, many mud-terrain tires feature large self-cleaning side lugs to improve traction and they can vary in aggressiveness. Mud-terrain tires often have features to eliminate stone retention and protect the rim, too. Manufacturers have a variety of different names for the features that accomplish these tasks. Mud-terrain tires offer top notch off-road traction and are the most durable, meaning they are built to excel at withstanding the rigors of off-road travel. Many work very well for rockcrawling because the large lugs can grip a ledge or boulder and pull the vehicle up, so obviously their benefits expand beyond just mud. Mud-terrain tires don’t perform as well on-road as an all-season or all-terrain tire, they wear faster, they’re noisier, and they may create a stiffer ride. Ultimately, these are small concerns for wheelers whose rigs spend the majority of time off-road and need the performance these tires offer.

Your rig doesn’t have to be a mega-built monster to benefit from mud-terrain tires. Many manufacturers offer mud-terrains in smaller sizes so your mildly modified rig can get you through the worst of terrain. Witness how nice these mud-terrain tires are self-cleaning on this Chevy S-10 Blazer.

Some examples of mud-terrain tires include:
BFGoodrich Mud-Terrain T/A
Cooper Discoverer S/T MAXX
Dick Cepek Mud Country
General Grabber
Goodyear MT/R
Interco Super Swamper TSL Bogger
Mickey Thompson Baja MTZ Radial
Nitto Mud Grappler
Pit Bull Rocker
Pro Comp Extreme MT
Toyo Open Country M/T
Yokohama Geolandar MT

Bottom Line
So which tire is better for your rig? Well that depends on what type of wheeling you do. If you drive your rig to work every day and explore old logging or mining roads on the weekends, you’ll probably be happiest with an all-terrain. If your rig never leaves the pavement except when you slide into the ditch on a snowy day, you may want to look at an all-season tire. However, if your rig is a trail regular or if it’s a dedicated trail rig you’ll want the ultimate performance that a mud-terrain tire offers.

Radial vs. Bias-ply
Radial tires use cords that are laid from bead to bead at a 90-degree angle to the direction of travel, preventing internal friction by eliminating plies rubbing against each other. Steel belts are then used in the tread for stability and tread squirm resistance. Bias-ply tires are typically constructed using nylon cords that create layers, or plies, that extend diagonally from one bead to the other. In other words, the sidewall and tread have the same construction. Each successive ply is laid at an opposing angle to the first, creating a crisscross pattern and strength is built using additional layers.

A radial tire will offer a pliable sidewall. A couple of features that go hand-in-hand with that are a strong carcass and cut and abrasion resistance like that found in the Cooper Discoverer S/T MAXX shown here.

Radial tires have lower heat, friction, and rolling resistance than a bias-ply tire. They’re also much more stable at speed, offer better steering feedback, and they last longer. They also allow for decent sidewall flex due to their inherent ability for the tread and sidewall to act independently of each other. They also don’t “flat-spot” like a bias-ply. Bias-ply tires have a stronger sidewall, better self-cleaning ability, and a generally softer compound that offers a better grip. Also, because of the way they’re constructed a bias-ply tire is just as strong in the sidewall as it is in the tread and the plies reinforce each other.

Bias-ply tires aren’t for everyone and ultimately there are far less bias-ply tires on the market than radials, but for the hardcore trail rig they’re a viable option.

Specialty Tires
The tire industry is responding to the needs of 4WD owners with specialty tires built specifically for certain types of wheeling. An example would be the BFGoodrich Baja T/A, which is built for high-speed desert running. For those who like to rockcrawl, there are tires like the BFGoodrich Krawler T/A KX and the Maxxis M8090 Creepy Crawler, and both have s super sticky tread compound. If you mostly use your rig on the street in the ice and snow, there are tires like the Bridgestone Blizzak DM-Z3 that has a special Tube Multicell compound to improve control on ice, a silica-enhanced tread compound, and special zigzag 3D sipes.

An all-season tire will actually work very well in sand when aired down. We explored the Outer Banks of North Carolina in this bone-stock Chevy Tahoe without any problems after airing the stock tires down to around 15 psi.

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