KINGS OF TRACTION
When the getting there is the most important factor in buying new tires
By Steve Campbell / ©2008 Editorial Services West (Photos by Bruce W. Smith-Smith-Walton.Com)
The truck was packed and we were heading deep into the backcountry to set up base camp. My two hunting partners and I had been looking forward to our annual trip for months, leaving our landscaping and construction jobs behind for a week of vacation in the Montana high country.
A recent rain had left the road in to our destination sloppy. But the Chevy 4×4 diesel we had chosen to take for this trip easily made its over the slippery surface until we slowed to round a sharp bend and encountered a spot where other passersby had obviously had trouble: Deep ruts had been churned up by previous drivers’ efforts to power their way across the obviously wetter and deeper 60-foot-lomg patch of muck.
As a precaution, a twist of the four-wheel-drive knob from “Auto” to “4H” electronically locked front and rear diffs for maximum traction, just as had been done hundreds of time on the job sites.
A good thing, too, as the tires began to spin the moment all four tires rolled into the ruts. But a light and steady throttle kept us moving until across to to firmer footing
The major contributor to the ease with which we traversed a section that had clearly caused problems for other drivers was the tires on our truck. While the “all-terrain” treads that come stock on most four-wheel-drive vehicles are great for paved surfaces and many off-pavement excursions, mud requires special technology—and that’s what was at the four corners of our truck.
And anyone who has traveled back roads and trails to get to a favorite spot during the fall and winter months knows, it’s not a question of whether you will find mud but rather how much and how deep.
The right tires will keep you on the road to your destination. The wrong ones will leave you wishing you’d made a better tire choice.
IT’S ALL ABOUT TREAD
Your basic OEM street tires are designed to be quiet, provide good adhesion on dry pavement, channel water away from the tread in wet conditions, and last for 60,000 miles.
Their tread consists of tightly spaced rubber patterns that give the largest possible contact patch with the road surface, and the blocks (lugs) are scored with jagged slits (sipes) that open as the tire flexes on the roadway and provide more gripping edges, which are particularly useful in wet or icy conditions. A “P” will be the first letter in the sidewall code of a passenger-car tire.
An “all-terrain” tire, such as those that come stock on most new four-wheel-drive pickups and SUVs, have a more aggressive tread pattern with slightly wider spaces (voids) between larger and more defined tread blocks, and they have stiffer sidewalls to better absorb off-road jolts.
These tires carry an “LT” (light truck) designation at the beginning of the sidewall code and an “AT” or “A/T” suffix at the end. Such tires work well in many off-road conditions such as moderate rocks, dirt trails, gravel and light mud, though they may need to be deflated somewhat (aired down) to provide better flotation with a larger, more supple contact patch in some conditions such as soft sand.
While they are slightly noisier than a purely street tire, they offer the best compromise for all-around use on city streets, highways and lighter-duty off-roading. (For advice about winter conditions, see “Snow Traction” sidebar.)
Mud tires, on the other hand, are built specifically to handle soft, often sticky combinations of water and soil. Mud tires are built with large, blocky lugs separated by wide voids to expel mud that would pack into narrower channels, freeing the lugs to continue to dig and paddle on the next rotation of the tire.
There are a couple of drawbacks to such an aggressive design. First, mud tires don’t offer as much adhesion on pavement because the big lug design means that there isn’t as much rubber in contact with the road as their A/T counterparts.
That’s especially noticeable during braking or hard cornering, where mud tires will lose grip more quickly than a street or all-terrain tire.
In addition, mud tires tend to set up a harmonic hum or roar on hard flat surfaces, created by the sound of air being forced out of the voids as the tire rolls and flexes on pavement. Harmonics can be mitigated somewhat by non-repeating (asymmetrical) tread patterns, but such tires will always be louder than tires with less aggressive tread designs.
RIDE SKINNY OR WIDE
All mud is not created equal. In fact, the texture and consistency of mud varies significantly from region to region, depending on the type of soil and the water content.
It may be deep and very sticky or develop as a layer only a few inches deep over a harder subsurface. It may be formed from fine sand or clay loam, be thin as soup or thick as mortar.
That’s why a pickup owner on the hunt for new tires should consider a specific tire construction according to the type of mud most commonly encountered, or causing the greatest traction concern. A sandy soil is a lot more foregiving when it comes to traction than its clay counterpart.
Where a relatively shallow layer of mud covers a harder substrate, a tall and narrow tire works best. The thin carcass carves down to where the traction is, and the open lug and void combination self-clean the tread for continuous grip.
But if the mud is too deep, that narrow tire will dig down until the differentials rest in the muck and the tires spin uselessly. The truck had better be equipped with a stout winch if that happens.
In thick, deep, gumbo mud, a wider tire provides greater flotation, meaning the tire’s larger footprint, or contact patch, spreads the load over more surface area (similar to how a track works). The effect can be enhanced by airing down the tires from their customary 30-35psi to 20psi, which is also effective in soft sand.
Where mud conditions vary, I prefer the wider style in the 10.50-12.50-inch range (31×10.50, 33×12.50, 35×12.50) with a variety of lug sizes separated by deep voids because such tire type provides bite where needed and will eventually dig through shallow strata while offering offer good flotation.
While a truck’s original equipment all-terrain tires are usually a great compromise, those who work in the construction/landscaping trades who consistently deal with adverse conditions during the late fall and early winter should consider making a switch to high-traction treads when their vehicles will see moderate to heavy mud areas.
For the rest of the year, those tires should be stored (see “Maintenance Matters”) and A/T tires slipped on in their place. That way, the initial tire investment can be easily doubled.
When tires are replaced, use matched sets of four. Mismatching tires — placing mud tires on the drive wheels and all-terrain tires on the non-drive wheels, for instance — can cause dangerously poor handling because of the differences in traction and adhesion.
For example, mud tires on the rear and “stock” tires on the front will cause your pickup to plow straight ahead instead of turning when you are driving over snow or through mud. The reason this happens is the tires on the back have far better traction than those on front. So they will push while the front tires slide.
Likewise, if the rear tires are older and have less traction than the fronts, the rear of the truck will tend to slide out, causing “oversteer.” This usually happens without warning and can result in just as disastrous consequences as having the front tires sliding.
Tires are constructed in two basic ways: bias ply and radial ply. The two designs have very different handling and ride characteristics.
Nearly every factory pickup and SUV tire is of the radial type, including all-terrains, because they have softer or more flexible sidewalls. The flex in the sidewall not only reduces rolling resistance, it also helps absorb road irregularities and promotes better raction, working in concert with the suspension.
Lower rolling resistance also improves fuel economy and increases tread life.
The downside is softer sidewalls are more prone to puncture than the heavier and more durable bias-ply sidewall. Thus, many all-terrain as well as mud tire manufacturers build in sidewall lugs or tread blocks that protect the side of the tire.
Meanwhile, many purpose-built mud tires are bias-ply types that take advantage of the stronger construction and can also be aired down with less chance of damage to the sidewall.
Originally, tires were graded by the number of plies used in their construction. As tire technology advanced, however, fewer plies were required to obtain the same strength, wear and durability characteristics. A ply number is still used for some modern tires — for instance, 4-ply, 6-ply, 8-ply or 10-ply — but the number refers to the strength and stiffness of the tire as a whole rather than its actual construction.
A numerically higher ply-rating generally indicates a more durable but harsher-riding tire and is related to the tire’s load rating, which may also be designated by an alphabet letter.
Most stock light-truck tires are C-rated; higher-capacity tires, which are designed for pickups equipped with campers or towing large trailers, are D- or E-rated. The higher up the alphabet a tire is rated, the stiffer the ride.
Sidewall dimension has also become more critical as the trend toward larger wheels has taken hold. The greater the diameter of the wheel, the shorter the sidewall must be for a tire of a given height.
Thus, a 20- to 24-inch wheel clad with low-profile radials might look spiffy on a lowered Escalade or Denali, but that same combination would be sidewall suicide in an off-road tire. Sportsmen should forgo the bling for the brawn, sticking with 16- to 18-inch wheels to accommodate a beefier sidewall and greater off-pavement performance.
The same, of course, for pickups used on job sites where the driving conditions are less than optimum.
MAKING GOOD CHOICES
Experienced drivers develop all sorts of techniques to deal with adverse terrain, but chief among them is making sure their vehicle is riding on the proper tires for a given purpose.
While stock all-terrain tires are perfectly suited to everyday driving and mild to moderate off-pavement driving, they are definitely not designed to deal effectively with the slip and slide of severe mud.
For that, you need a purpose-built tread that will claw and clean its way through the worst slop and greasiest gumbo. Mud tires also work quite effectively in very rocky terrain—and can get through soft, sandy conditions if you air-down and let floatation be your ace-in-the-hole.
As for which brand to buy, watch how your buddies’ trucks and SUVs handle adverse conditions. If you see a tire that you like, take a ride in a vehicle equipped with them to see how loud the road noise is and how they feel both on- and off-pavement.
And if money is tight, don’t hesitate to shop for “regional” brands, which are probably made by one of the bigger tire manufacturers and branded with the lesser-known tire company’s name on the sidewall. Another good way to save on a tire/wheel purchase is to compare local tire prices against those package specials offered by the larger off-road parts stores and e-tailers.
Never underestimate the importance of tire pressure. Under-inflated tires reduce gas mileage, cause uneven and accelerated wear and reduce the vehicle’s load-carrying capacity.
Because rubber is permeable, tires lose about 1psi per month and about 1psi for each 1°F of temperature drop, so they should be checked every month, preferably with a digital gauge for accuracy.
The correct air pressure is noted in the vehicle owner’s manual and is also be found on an information sticker located on the driver’s doorjamb or the fuel-filler door. (Do not go by the tire pressure indicated on the tire sidewall, which shows only the tire’s maximum inflation pressure.)
The information sticker also shows the vehicle’s load limits, which should be adhered to for safe operation.
Tire pressures should be checked cold, and the spare should be checked along with the mounted set. Tread depth should also be checked regularly by inserting a penny upside down into one of the tread channels. If the top of Lincoln’s head is visible, the tire is at the end of its life.
Rotate tires at least every 8,000 miles. Tires wear differently in different locations on the vehicle. Rotating evens out the wear and extends tire life.
When they’re not mounted on the vehicle, store tires in a cool dry place indoors and away from heat sources and substances that may deteriorate rubber, such as solvents and gasoline or generators that produce ozone. Tires stacked too high may tumble, so limit stacking height to 5 feet.
After use off-road, clean mud and debris off the rims (and the rest of the vehicle). Mud can unbalance the wheels and retain moisture, causing rust, scratching and wear. – BWS
Not all pickup owners face mud, rock and san in their adventures. Those in the snow belt face a lot of white and ice. Driving in those conditions requires special tires—not those factory “All Season” donuts.
There are two basic schools of thought about what makes the “best” snow tire. One says a good traction tire will handle snow equally as well as mud — but that works only if the snow is wet and heavy, like mud.
On the other hand, dry and light snow sticks to itself a lot better than it sticks to rubber. In those conditions, a better bet is a tire with small blocks, narrow voids and lots of siping where the snow will pack in and stay put, building up a layer (like rolling up a snowball) before shedding some of the accumulation to make room for more.
“All-Season” radials, indicated with a variant of the letters “MS” on the sidewall, are compromise tires that work adequately in most winter conditions and on dry pavement but not superbly in either case.
What you want in heavy snow areas are true snow tires—those marked with a mountain/snowflake symbol on the sidewall.
The best snow/ice tires for a sportsman’s pickup or SUV are the following: Nokian Hakkapeliitta Sport Utility 5; Michelin Latitude X-Ice; Bridgestone Winter Dueler DM-Z2; Bridgestone Blizzak WS60; Nokian Hakkapeliitta LT; and the Nokian Hakkapeliitta SUV.
These tires can be purchased through a number of tire stores, or on the internet. Check these sources if you can’t find what you’re looking for in ice/snow tires: www.tirerack.com; www.tiresbyweb.com. —Bruce W. Smith