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Conquering Off-Road: Limits of Geometric Cross-Country Ability and Proper Use of Wheels

In off-road adventures, the correct use of tire properties guarantees maximum efficiency. The vehicle’s cross-country ability can also significantly increase, with geometric capabilities complemented by the reliable grip of the wheels on the ground. The all-terrain qualities of your car will not change too much, as if you add another pair of wheels, like on a dually truck, but it is possible to use them to their fullest extent.

Geometric cross-country ability of the car

The first thing that determines the SUV’s cross-country ability is ground clearance б it’s the minimum distance from the ground to the lowest part of the vehicle. Typically, such lowest item is the rear axle gear housing or suspension arms. Sometimes a muffler. Ground clearance makes it possible to understand the height of an object that can be safely passed between the wheels or the depth of a rut that you can surmount without getting stuck.

It would seem that the choice of tires cannot influence this parameter. However, the off-road SUV and truck experts from Indy Auto Man note that if the tires have a powerful straight grip and an aggressive sidewall, then in the case of soft ground, the car will crawl on its belly, clinging to the ground with the tread. And, if the soil is soft and your vehicle is sufficiently protected from below, there is no need to worry about damage. Read how to choose the right tires on indyautoman.com.

Approach and departure angles

Other, no less important parameters of cross-country ability are approach and departure angles and the length of the front and rear overhangs. They give an idea of what kind of obstacle, for example, a step or a steep hill, the car can drive into and out of without the help of sand trucks. However, they can also be overcome by cunning, using the tire hooking. For example, if a car rests its bumper on a high ledge (step, log), then in many cases, you can approach from the side at an angle. By turning the front wheel towards the obstacle, we significantly reduce the angle required for entry and neutralize the length of the front overhang. And we hit the obstacle not with the bumper but with the wheel. The aggressive shoulder sipes of the tire crawl onto the step, leaning like a person on their elbows.

The same happens when driving off a step at an angle – the car does not hit the bumper, and a good grip helps you avoid slipping and falling. It is crucial at this moment to select the correct tire pressure. High pressure is not suitable for this type of work. It does not allow the tire to wrinkle and wrap around an obstacle, including the lug lamellas, but forces it to turn. Trialists, for example, set the pressure in the front tires to within 0.45-0.35 atm on rocks and concrete blocks, and in the rear tires – even lower. But if your car does not have special locks on the rims (padlocks) that allow you to hold the rubber on them, you should not reduce the pressure below 0.8 atm. For regular wheels and medium-sized tires (31-33 inches), 0.5 atm will be critically low, and there will be a danger of the tire spinning on the rim, after which you will have completely different problems.

How to overcome obstacles

So, most geometric obstacles, such as a step, a stop, a ditch, or a log lying across the path in the forest, are better to attack at an angle and overcome diagonally. As for the log, if its thickness exceeds the ground clearance, it is better to remove it from the way, using the SUV as a tractor. If the log approximately corresponds to the ground clearance, you can take a risk, not forgetting that steel is always stronger than wood, but you risk torning off the muffler. If the log is not very thick, you can move it, choosing a trajectory at a slight angle. However, if the selected angle is too large, and the log and soil are slippery, the vehicle can easily slide, and the log will stand along the track. In this case, you should stop and reduce the tire pressure. Otherwise, you will forever slide along the log. Low pressure and aggressive side sipes of the tire mud tread will do their job, and the car will climb onto it.

When moving in a ditch, especially a deep one, the absence of inter-wheel locks can immobilize the car at diagonal hanging. Therefore, enable the necessary options in advance if, of course, they exist. If not, then having chosen the optimal, in your opinion, trajectory for moving, use inertia and do not let the car stop at the moment when the wheels hang diagonally. Thus, you can overcome many obstacles with the correct use of tires with a good grip. Just remember these recommendations and practice regularly.

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