If you want to take full advantage of the traction provided by your truck鈥檚 four-wheel-drive system, you need to run a tire designed to grip the surfaces you drive on. And if those include both paved and unpaved roads, the tire you鈥檙e looking for听is an all-terrain. Let me save you a bunch of money, hassle, and headaches, and show you how to find the right one for your specific needs.
What Is an All-Terrain Tire?听
鈥淎n all-terrain tire is a jack of all trades, and a master of none,鈥� says Todd Bergeson, the senior manager of product planning at . Bergeson is responsible for engineering听the tires my wife runs on her long-travel Land Cruiser,听and听he participated in the design of that vehicle鈥攂efore joining Toyo, Bergeson worked as an engineer and product planner at Toyota. His r茅sum茅 also includes听other well-regarded 4x4s, like the 4Runner TRD Pro听and the FJ Cruiser.
What Bergeson is getting at is that,听while other tires may outperform all-terrains听on snow, dirt, or pavement, nothing else is designed to work as well across all those surfaces.
Compared with听a highway tire, an all-terrain tire will be equipped with a stronger bead (a ropelike ring that runs around the inner perimeter of the tire, holding it onto the wheel rim), tougher plies (the panels of steel or fabric mesh that lie under the rubber, adding strength and puncture resistance), as well as a rubber tread that鈥檚 thicker and designed to better withstand the cutting, tearing, and deformation caused by off-road surfaces. The pattern of that tread will also be designed to grip loose surfaces, while evacuating water, mud, small rocks, and snow as efficiently as possible.
Unfortunately, all those traits do come with some trade-offs. Compared with听a highway tire, an all-terrain tire will be heavier and louder听and won鈥檛 offer quite as much grip on pavement. Bergeson听says听that more new vehicles don鈥檛 come听equipped with all-terrain tires for just those reasons. 鈥淢ost drivers don鈥檛 actually use their 4x4s off-road,鈥� he says. 鈥淎nd they still want their trucks to be competitive with other vehicles.鈥�
Consumers who buy rugged听SUVs听or pickups with the expectation听that they鈥檒l听drive like a luxury car or a sports car often dictate the tire choices made by car manufacturers. If you bought an SUV or a pickup truck听with the expectation听that you鈥檒l be able to use it off-road听and in winter weather, you鈥檒l need to change those tires.
What鈥檚 the Right Size?
Larger tires will more easily roll over larger obstacles off-road. They also look cool. Unfortunately, larger tires will also reduce a vehicle鈥檚 effective gear ratio. As I wrote about at length in an article about people ruining their Tacomas, that can utterly destroy a vehicle鈥檚 fuel economy, performance, and off-road capability.
Want to see the effect that fitting a larger tire size will have on your vehicle鈥檚 performance? .
(Original tire diameter) / (New tire diameter) x Vehicle axle ratio = Effective axle ratio with new tires
So听if you鈥檙e switching from the 30.5-inch tire that comes standard on a Tacoma听to a 34-inch tire, given the Taco鈥檚 3.91 gears, that will give you a new effective ratio of 3.50 to 1. Your performance will decrease by 11 percent.
It鈥檚 hard to picture what that will look like in the real world, so听this formula will help you understand that:
(Original tire diameter) / (New tire diameter) x RPM@MPH = New RPM at that speed
Again, using the same Taco example, switching from a 30.5-inch tire听to a 34-inch one听will reduce engine revolutions at 60 miles per hour from 1,500 to 1,345 revolutions per minute. That鈥檚 also an 11 percent difference. Take that into the real world and see how your engine and transmission perform at the different RPMs. Just remember that the effects of altering your final drive ratio with larger tires are compound; while your engine will be operating at lower RPMs听at a given road speed, it will also have less power.
Wondering how much height a taller tire will add? Fortunately, that calculation is a lot easier. Simply divide the difference in tire diameters by half, and that will give you the increase in height that changing the tires alone will give you. This can be important in determining whether or not your truck will fit in your garage.
What I can鈥檛 give you a formula for is how well a larger tire will fit on your vehicle. For instance, mounting (which actually measure out at 33 inches) to my Ranger required a two-inch suspension lift, chopping off the wheel-crash bars, and using wheels that spaced the tires听outboard. And they still rub at full lock in reverse. Every vehicle and every suspension setup will be different, and the skill of your alignment shop plays a role in tire fitment, too.
Does all that sound like a real pain in the butt? It is. There is no possible outcome here in which increasing your tire size does not cost you money听and create an unnecessary hassle. So听instead of trying to fit a larger size when you switch to an all-terrain tire, I鈥檓 going to make a controversial suggestion here: don鈥檛. The best听all-terrain size for you is almost certainly the tire size your vehicle left the showroom with.
What About Load Ratings?
And you thought sizes were complicated! All-terrain tires come in three varieties, based on the loads they鈥檙e designed to handle: P/Euro-metric, LT, and flotation.
A tire鈥檚 load capacity is determined by how much air it鈥檚 designed to hold. P/Euro-metric all-terrains come in either standard load (denoted by an SL or nothing in the tire鈥檚 size description)听or extra load (XL in the size description). SL tires can be inflated to 36 pounds per square inch (psi), while XL tires can hold 42 psi.
In either case, you should look up your vehicle鈥檚 gross vehicle weight rating (GVWR), found online, inside your doorjamb, or in your owner鈥檚 manual, and make sure any tire you fit is designed to support at least a quarter of that weight.
鈥淭hink of a tire like a balloon,鈥� says Bergeson. One designed to hold less air can be made thinner and lighter. One designed to hold more will need to be thicker and heavier.
LT stands for light truck (you鈥檒l see LT ahead of the tire size). In this verbiage, this denotes anything shy of a commercial vehicle. LT tires come standard on heavy-duty pickups, like the Ford Super Duty. The load capacity of LT tires is denoted by letters, typically B, C, D, E, or F. In the past, these letters indicated the number of plies used in the tire鈥檚 construction鈥攊n听that same order: four, six, eight, ten, and twelve听plies. With modern materials, that鈥檚 no longer the case. High-strength steel, nylon, or polyester plies don鈥檛 need to use as much material to provide an equivalent capacity to the cotton plies of yore, so tires now feature a ply equivalent rating. An E-rated tire, for instance, can now hold as much air as ten old plies, using just three plies made from modern materials. All you need to understand is that B-load tires can hold the least air, and therefore support the least weight, and that progresses on up to F, which can hold the most air听and therefore support the most weight.
As a tire鈥檚 load capacity increases, so does the air pressure it takes to fully inflate it. Where the maximum pressure on a standard-load P/Euro-metric tire is 36 psi听(consult the table inside your vehicle鈥檚 doorjamb for recommended pressures;听they鈥檙e typically a little lower than the maximum), the max pressure for an E-rated LT tire is probably 80 psi.听(On LTs, maximum pressures vary with tire size.听I鈥檓 glossing over some technicalities for brevity.)听Not only will that be a thicker, stronger balloon, but inflated to sufficient pressures, it鈥檒l also be a stiffer one. On the road, you鈥檒l feel that. The thicker, stronger听carcass of an LT tire, inflated to a higher pressure,听will deform less over small bumps than a P/Euro-metric one, transmitting those movements to the suspension. And not only will more bumps reach the suspension, the momentum of that heavier tire will also be greater, so those bumps will effect the suspension more severely. It also takes more energy to accelerate or decelerate a heavier tire. All that听to say: compared with听a lighter P/Euro-metric tire, a heavier LT tire will worsen your vehicle鈥檚 ride quality, make it slower, and increase your braking distances.
It鈥檚 important to emphasize here that听if you upgrade from the P/Euro-metric highway tires that likely came with your vehicle to an aftermarket LT tire, you鈥檒l need to run higher pressures than is suggested by your vehicle manufacturer on the road. LT tires require more air听to reach optimal levels of inflation; fail to inflate one fully and the tire鈥檚 tread will cup inward听rather than make uniform contact with the road. This will cause your tires to wear prematurely and create an awful lot of noise, and that reduced contact patch will combine with the soft, underinflated sidewalls to entirely ruin your vehicle鈥檚 handling. to determine the correct pressures for your LT tires.
But听carcass strength isn鈥檛 the only thing separating P/Euro-metric all-terrains from LT ones. Bergeson听says听that Toyo uses different compound materials for the two categories of tires, as well as听different tread designs.
鈥淥ur data says P/Euro-metric users spend at least 80 percent of their time on paved roads,鈥� he says. So Toyo optimizes those tires for that use. On its new , for instance, Toyo employs a rubber compound with a higher proportion of silica, which enhances grip on wet pavement. And听the tread pattern features smaller voids听and more siping. (Sipes are the squiggly little lines inside the tread blocks.) The noise you hear all-terrain tires make is created by air passing through those voids. So making sipes听smaller on tires biased to听on-road use helps make those tires more civilized. Sipes enhance mechanical keying on slippery surfaces like ice, so adding more of them helps the P/Euro-metric AT/IIIs perform better in winter conditions.
I asked Bergeson if the thinner, more flexible construction of a P/Euro-metric tire was less suitable for off-road use. 鈥淵ou鈥檒l actually find that the more flexible tire deforms better over obstacles, which can help with grip and ride quality,鈥� he says. It鈥檚 not true that plies used in those tires can lead to more punctures. While the strands used to construct the lighter tires aren鈥檛 quite as thick, they鈥檙e more densely woven, which works to prevent penetration equally well. The one area where an LT tire might be more resistant to punctures than the lighter option will come simply from increased thickness of the tread on the former.
Where a P/Euro-metric AT/III is equipped with a tread depth of 13/32nds of an inch, the tread on LT sizes is 16/32nds of an inch deep. That means the rubber that the LT tires drive on is that much thicker. It鈥檚 also made from a different compound, with a lower silica content, and uses a tread pattern with larger voids听and fewer sipes. Bergeson says that these changes are intended to increase the LT tire鈥檚 durability and performance off-road. Not only is the lower-silica-content compound more resistant to cuts, tears, and deformation caused by sharp rocks, but the larger voids are better at ejecting those rocks before they can cause damage. Fewer sipes are also less prone to picking up听and being damaged by very small stones. With fewer of those sipes, the tread blocks on LT AT/IIIs better resist deformation, which restores some of the steering feel and stability lost by the larger voids. But听those larger voids听enhance traction on loose surfaces like mud.
Notably, equipping LT tires with the ability to contain higher air pressures also gives them one feature that really helps off-road: because all that extra air requires a thicker, stronger bead, LT tires mount more securely to their wheel rims. This lets drivers safely run lower pressures off-road.
Which brings us to flotation sizes. Whereas P/Euro-metric and LT sizes are listed in metric sizes (285/75R17 for instance), flotation sizes are listed in imperial specs (35×12.5R17). They鈥檙e typically produced in loads ranging from C to E听and are usually available only in wider widths. Flotation tires are the most off-road-oriented all-terrains. Flotation AT/IIIs, for example, use a 17/32nds听tread depth听and even larger voids than the equivalent LTs. So听they also require high on-road pressures听but will be even more durable off-road, and even noisier on. Because they鈥檙e so wide, flotation sizes typically only fit modified trucks.
Running P/Euro-metric all-terrains in your vehicle鈥檚 stock tire size is the easiest, most effective way to gain traction off-road and in winter weather听without sacrificing too much in the way of road manners. Bergeson recommends only upgrading to an LT tire if you drive a lot of gravel (or if the weight of your vehicle dictates it). All the tiny, sharp, rolling rocks in that surface represent a unique challenge to tires, and it鈥檚 one the compound听and voids used on the LT AT/IIIs are听specifically designed to handle.
What Are the Best All-Terrain Tires for You?
Beyond size and load capacities, there are听a couple other markings you need to consider.
Dial in the Mud and Snow Factor
The first of those is the M+S stamp that鈥檚 present on most all-terrain tires听and also many highway tires that advertise themselves as appropriate for mud and snow. The M+S standard is 听and is self-reported by tire makers, not certified by any independent body. To merit this stamp, a two-dimensional analysis of a tire鈥檚 tread pattern must demonstrate that at least 25 percent of the tread鈥檚 surface area is made up of grooves. M+S reflects no actual designed, intended, or tested traction in mud or snow, just that 25 percent groove area. Don鈥檛 rely on an M+S stamp to tell you anything about a tire鈥檚 performance.
Conversely, the 3 Peak Mountain Snowflake (3PMSF)听does 听to an actual American Society for Testing and Materials standard, but it is still self-reported by tire makers. And while 3PMSF is used by authorities to legally define a winter-capable tire, that鈥檚 a very limited standard. To score听a 3PMSF rating, a tire only has to demonstrate traction on packed snow that鈥檚 10听percent superior to a reference tire, that reference tire being a bargain-basement highway all-season tire from the early 1990s. Running a 3PMSF stamp may allow you to legally drive into Lake Tahoe, California,听in the winter in a four-wheel-drive vehicle without snow chains, but it does nothing to guarantee that your drive will be safe.
Until such a time that adequate performance standards for tires are enacted, we as consumers have to work with听tire-maker claims, customer reviews, and independent tests conducted by enthusiast publications. If that doesn鈥檛 sound like an ideal situation for finding objective guidance around choosing the single most important component on your vehicle, I鈥檓 with you.
How I Pick the Best All-Terrain Tires
My method for picking an all-terrain tire is to first figure out what size and load capacity I need, then to look around for the tire with those听numbers that has听been developed most recently. Assuming that materials and manufacturing technologies advance over time, I figure that should result in the latest and greatest product. But听just to be sure, I鈥檒l pull up a tire鈥檚听specs听and compare them with competitors. The point of comparison that鈥檚 most important? Weight. For all the reasons described above, a lighter tire is a better tire听if it otherwise provides the load capacity, durability, and traction you require.
And that鈥檚 how I ended up putting on my wife鈥檚 Land Cruiser. That tire was released last March, and in the LT275/70R18 E size听that听works best with the very complicated custom-suspension system on that truck,听the 53-pound AT/III is four pounds lighter than the 鈥攁nd over seven pounds lighter than the .
鈥淏ecause we manufacturer the tire in America, we鈥檙e able to very carefully place rubber only where it鈥檚 needed,鈥� said Bergeson听when I asked him to account for that weight difference. He went on to explain that the AT/III鈥檚 light weight is achieved without sacrificing puncture resistance. Tread depth isn鈥檛 compromised on the design.听Plus,听the unique method by which the company layers its plies ensures that, while the E-rated AT/III is technically a three-ply tire, the plies overlap behind the tire鈥檚 sidewall, effectively protecting that area with six plies, while helping the tire retain better stability on the road.
Those merits have been听borne out in my time driving on those tires. That they鈥檝e proven trouble-free off-road should be expected. What鈥檚 surprising is how good they are听on dry pavement, on the road in rain, and on packed snow, too. Since we live in Montana, I still switch听to a dedicated winter tire for that season, but running the AT/IIIs in the shoulder seasons allows us to confidently tackle even significant snow events without concern.
My one prior听frustration with that vehicle had been how invasive听and lurch-prone its traction-management system is. But听the level of grip provided by the AT/IIIs has smoothed it out听and made it more effective听and seamless in operation. I had no idea when I selected听the tires that they were engineered by one of the guys who helped develop the Land Cruiser, but now that I know, it鈥檚 not a huge surprise that they鈥檙e the perfect match for the vehicle.
The Bottom Line: Best All-Terrain Tires
What are the best all-terrain tires for you? Run through the formulas I listed above to determine the right size.听Then听decide whether or not your use case is more on-road听or off, and choose either P/Euro-metric or LT tires to suit. (Consider a flotation size if you drive a highly modified truck.) See if you can find a lighter tire than the AT/III, and if you can鈥檛, run those. Don鈥檛 be surprised if those tires make your truck feel brand-new, too.
(If you drive an all-wheel-drive crossover, I still recommend the . It鈥檚 the only all-terrain tire actually designed to work on Subarus听and the like.)