The Role of Air Pressure in Rugged Terrain Tires

But why? Is there a problem with the tires? Did the driver ignore a series of low-pressure warning lamps? Can I possibly work any more question marks into this paragraph? The answer to all those questions is negative. In fact, the tire’s appearance is quite intentional and serves as a great tool with which to grab a skiff of extra off-road traction from the already capable rugged terrain type of tire. Allow us to explain.

While not generally given much thought, the air inside a tire plays a vital role in supporting the vehicle and dictates how the tire interacts with the surface into which it is being pressed and is generally measured around these parts in pounds per square inch (PSI). Having too much of the stuff in a tire is called overinflation and can diminish how much tire surface, referred to as a contact patch, touches the driving surface. This can lead to reduced grip and odd wear.

Conversely, too little air pressure can make a larger and wider contact patch, creating extra rolling resistance the vehicle must overcome to maintain speed. Think about how difficult it was to pedal yer bike as a kid when there wasn’t enough air in its tires. The same principles apply.

But in an off-road situation, it can be advantageous to have a less-than-normal amount of air in one’s tires – particularly when navigating soft sandy surfaces or scampering up some slickrock at Moab. Reducing tire pressure (airing down, in off-road parlance) is a way to intentionally increase the tire’s contact patch, spreading the vehicle load over a wider surface area of rubber and permitting more elements of a tire’s tractive properties to be in contact with the ground.

In fact, tire companies have long caught on to this practice and have begun adding gripping surfaces to the sides of rugged terrain tires. The Saliun Terramax RT, for example, has a squared profile and staggered scalloped shoulder lugs with stone ejectors to maximize traction while removing debris in the voids. This is designed to dig into tough terrain when aired down. Other brands like BFGoodrich with its legendary KO2 and Nitto with the Ridge Grappler incorporate the same tricks to tremendous effect. It’ll take some creative or clueless wheeling to completely stymie these tires when properly inflated for the conditions. As a bonus, an aired-down tire will ride a bit smoother, as well.

Speaking of, finding the correct tire pressure for all conditions can take a bit of trial and error. This is why it is a decent idea to ask other drivers who have tackled the particular off-road obstacle you’re about to traverse for a bit of advice, or at least pay attention to posted suggestions in popular off-road areas like Moab or on the Rubicon. Invest in a high-quality tire pressure gauge (no, one from the dollar store doesn’t count) since they often include a deflator setting which can take a tire’s PSI down to a very specific measure. There’s no substitute for experience, so keep a few notes in yer phone or on a scrap of paper tucked into the console of your rig as reference points for the next time out.

Most off-road gearheads will suggest a higher pressure for rocky terrain than for sandy surfaces in order to ward off punctures and rim damage from jagged outcroppings. A lower pressure helps tires adapt and all but mold to the terrain, effectively gripping rocks and such like a human closing their fingers over an obstacle. Plus, slashing a sidewall far from roadside assistance is no joke. Meanwhile, the aforementioned sand (or mud) conditions often benefit from a relatively low tire pressure to promote better flotation. That said, if one plans on travelling at sustained felonious speeds on dunes, too little inflation can cause damage and loss of steering control

Generally speaking, it is better to err on the side of caution and not stray too far from the recommended pressures which are generally listed on a sticker in the driver’s door jamb of a vehicle. One can usually deflate their tires a bit further, if it safe to do so, more easily than adding air on the fly. Considering the last point, you’ve remembered to pack a portable air compressor to air up those rugged terrain tires after wheeling, right? Remember to immediately pump the tires to recommended factory pressures once returning to surfaced roads so you’ll have a safe drive home.

[Images: Manufacturer, Tricky_Shark/Shutterstock.com]

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