How Off-Roading Works


Off-Roading Image Gallery Driving on paved roads might be a snooze after climbing the sand dunes in the Wonder Desert of the United Arab Emirates. See more off-roading pictures.
Hamish Blair/Getty Images

For most people, a bumpy, muddy, rocky road would be a driving nightmare. But for some, the rougher the road the better. In fact, for a group of adventurers known as off-roaders, no road is best of all.

Off-roading is a term used to describe driving on unpaved ground. This surface can be almost anything other than typical smooth pavement, including fields, riverbeds, muddy bogs, sand dunes, beaches, mountainsides, gravel, boulders and even roads that have fallen into disrepair. If it's not paved (or paved well), it's fair game for off-roaders.

Some off-roaders enjoy the natural scenery, while others love the technical challenge that driving on unpaved ground presents. Whatever type of off-roading you're into, it can be a great pastime as long as you know what you're doing.

The natural terrain is uneven and can be unpredictable, so it's important that you have the proper equipment for off-road driving. While technically you can go off-roading in any vehicle, trucks, SUVs and other high-riding vehicles are best suited to handle the bumps and bruises found off the beaten path. You might also want to use four-wheelers, dirt bikes, dune buggies or all-terrain vehicles (ATVs), which are specially designed for off-road driving. If you're taking up off-roading as a hobby, a low-riding compact car probably isn't going to cut it.

Depending on what type of off-roading you're into, the type of vehicle -- and vehicle modifications -- you will need can vary. For instance, the same tires you use to drive over steep sand dunes probably aren't going to be great for traversing boulders.

One of the best things about off-roading is that you get to adopt a new vocabulary. For example, are you into mudding, rock crawling, dune bashing or green laning? Do you know the break-over angle on your car? Do you know how to pick a good line? Find out more about these terms and what they're all about in the next sections.

The Physics of Off-Roading

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One of the most important factors for success in off-roading is traction, or the grip your tires have on whatever surface you're driving on. Traction is largely affected by the type of tires you're using, their size, and their air pressure, as well as whether you're using four-wheel drive (4WD). For instance, some tires have bigger treads meant to give you better traction when driving in mud. And using 4WD gives all four of your tires better grip and control on the ground. Lowering the air pressure of your tires also increases traction because it allows more of your tire surface to grab onto whatever you're driving over.

Momentum also factors into off-roading. Momentum -- the mass of your vehicle multiplied by its velocity (speed) -- gets you to the top of a hill. Although the mass of your vehicle is fixed (mostly), you can control your speed. Friction with the ground and the force of gravity acting on your vehicle kill your momentum. And you don't want that to happen, unless you like being stuck on a hill.

Before going off-roading, you'll want to be familiar with three different angles on your car: the approach angle, the departure angle and the break-over angle. Knowing your vehicle's angles will help to keep you from scraping it on rocks and other obstacles or getting stuck.

If you're going off-roading, you first need to understand some basic principles about how your car interacts with the outside world. Traction, momentum and your car's angles each play a part in getting you over, or through, the obstacles in front of you. 

Picture yourself driving a car toward a ramp. If the ramp is too steep, your front bumper will hit the ramp, like a wall, before your tires are able to reach it. The maximum angle (from the ground) that a hill or obstacle can have and that the front of your car can still clear is called the approach angle. The same principle applies to the rear bumper and wheels on your car; this is the departure angle.

Likewise, when coming down off, say, a rock, you have to know how much clearance you have in your car's midsection so that it won't scrape the rock. The angle between your tires and the middle of your car's underside is dubbed the break-over angle. If you don't know the break-over angle of your car, you can wind up balancing on a rock like a teeter-totter with all your wheels off the ground.

All of these factors are important to off-roading, but they differ depending on where you're driving. We'll address that next. We'll also find out what kind of off-roading you're into.

Mudding

If you’re brave enough, you could always go mudding on a bike. Just prepare to get really, really dirty.
If you’re brave enough, you could always go mudding on a bike. Just prepare to get really, really dirty.
Michael Kienzler/Bongarts/Getty Images

Have you ever seen a big muddy pit and wanted to drive through it, spinning your tires and making the mud sling everywhere? Do you embrace your car being caked in layer upon layer of dirt? Then you might be into mudding.

Mudding, also known as mud bogging, mud slinging or mud racing, is a type of off-roading that centers on getting dirty. In its simplest form, mudding just means driving through its slimy, grimy namesake.

Mudding is tricky for the simple fact that you don't always know what's hidden under the mud -- rocks, tree trunks, anything you can imagine. There are also many types of mud, from thin and soupy to thick and slimy. In fact, driving in two different kinds of mud can be as different as driving on sand and ice. Each type of gunk presents its own challenges and requires variations in your driving technique.

This brand of off-roading hinges on maintaining and controlling your speed: You want to drive fast enough so that you'll make it through without stopping or sinking, but slowly enough so that you can manage any hidden obstacles beneath the mud. And if you do come to a stop, getting moving again in mud is difficult because it is hard to gain traction on such a slippery surface. If you're not careful, you might wind up spinning your tires and digging yourself deeper into the muck.

The key to mudding is maintaining a steady speed the whole way through. How fast you drive when mudding really depends upon the type of mud you're in and your vehicle. The important thing is to assess the terrain and make a safe judgment about your speed.

While you can go mudding with just about any tires, specially designed mud terrain tires are the best. Mud terrain tires have extra large lugs, or the part of the tire treads that sticks out, with wider and deeper spaces in between them. This arrangement keeps mud from getting stuck in between the lugs, allowing you to maintain traction.

Mudding is so popular that there are even mudding competitions. Organizations like the National Mud Racing Organization, the American Mud Racing Association and the Championship Mud Racing Organization have been holding mud racing competitions throughout the United States since the 1970s. With competitive mudding, the object is to see either how far you can drive through a muddy pit before getting stuck or how fast you can drive the entire length of the pit.

Mud isn't the only type of ground that you can sink into; sand can get you stuck as well. Read on to find out the basics of scaling sand dunes with your off-road vehicle.

Dune Bashing

The Sespe Condor Sanctuary in Los Padres National Forest, Calif., isn’t eager for off-roading enthusiasts.
The Sespe Condor Sanctuary in Los Padres National Forest, Calif., isn’t eager for off-roading enthusiasts.
David McNew/Getty Images

Dune bashing involves guiding your off-roading vehicle over sand dunes. In technique, it's like a combination of driving in mud and driving over hills. It's a popular tourist activity in parts of Saudi Arabia and the United Arab Emirates, where sand dunes are plentiful and organized dune bashing excursions are available, but is illegal in many places where off-roading has been deemed a threat to the dunes.

When scaling sand dunes, like any hills, knowing your off-roading angles is important. If you don't know your approach angle, you might wind up bumper-first in the sand. If you don't know your break-over angle, you may become stuck at the top of the dune.

Momentum also figures prominently in dune bashing. Like any hill, you have to gain enough momentum to reach the top without stopping. If you do start to slow, you'll have to either back down the dune or make a wide arc to turn around. Turning around on any hill is extremely dangerous because you're at greater risk of rolling your car over and ending up upside down. Cars are designed so that they are less at risk of rolling over if they are pointing directly uphill or downhill. When they sit sideways or at an angle, they're more likely to tip.

Wider tires work best for dune bashing. Think about how a snowshoe works: The wide shoe disperses your weight across a larger surface area, making it easier for you to stay on the surface and not sink too far into it. The same principle is true for tires -- the wider the tire, the less you will sink into whatever you're driving through. Dune buggies, special recreational vehicles designed to drive on sand, tend to have wider tires for this purpose. In addition, reducing your tire pressure can help to give your tires a wider surface area.

You also might encounter hills when you're green laning. Read on to learn why green laning is a popular pastime for even the non-hard-core off-roaders.

Green Laning

Cruising through the "Land Rover Experience Center" in Wuelfrath, Germany, looks pretty fun. These centers teach off-road driving skills to amateur and pro drivers.
Cruising through the "Land Rover Experience Center" in Wuelfrath, Germany, looks pretty fun. These centers teach off-road driving skills to amateur and pro drivers.
AP Photo/Michael Sohn

Green laning is typically the mildest, least technical type of off-roading. It involves driving anywhere without a paved road -- usually forest trails, the countryside or on roads that have fallen into disrepair. The name green laning comes from the fact that the path you're driving on is likely to have lots of natural (green) vegetation. Many people enjoy green laning because of the adventure and scenery involved in taking a trip off the beaten path, but without risking too much damage to their vehicle.

Green laning does have a reputation for causing another type of damage: damage to the environment. If the driver isn't careful, driving in the wilderness can harm plant life, tear up paths used for horseback riding and cycling, erode the ground and scare or harm wildlife. For these reasons, it's important to know the laws where you go off-roading, as well as take care not to cause unnecessary damage to the natural environment. You can minimize your impact by driving slowly and always being aware of where your tires are falling.

Off-roading enthusiasts like green laning because it usually requires few or no vehicle modifications in order to enjoy it. In most cases, no special tires are needed. You'll still want a higher-riding car, however, because there's a good chance of encountering small rocks and hills that a lower car might not be able to clear. Green laning is also great for four-wheelers and dirt bikes.

Holes and ditches pose the biggest threats in this type of off-roading. When approaching a ditch, you want to approach at an angle, not head-on. That way, one tire at a time will cross it, while the other three remain on a surface where they have traction. Approaching any obstacle head-on could mean that both of your front tires will lose traction at the same time, which could cause you to slip. The same is true for any obstacles you might come across, including logs and rocks.

If green laning seems too mild, read on to learn about rock crawling, arguably the most challenging type of off-roading there is.

Rock Crawling

One of the most challenging forms of off-roading is rock crawling, or driving over rocks: small rocks, big rocks, boulders and even mountainsides. The activity requires precision, planning and prior knowledge of your vehicle.

The key to rock crawling is the speed at which you slowly pass over the rocks; thus, the "crawling." Some recommend crawling at no more than 3 miles per hour (4.8 kilometers per hour) [source: DeLong]. Unlike mudding, speeding over rocks can get you stuck or damage your car. With rock crawling, you have to maneuver your car precisely; you need to know exactly where your tires will fall at all times.

Off-roading involves a lot of picking your line, or planning out the path you are going to take before you start driving it. This level of forethought is especially important in rock crawling, since you need to make sure your path, or line, can be managed by your vehicle. Sometimes you might want to get out and walk the line first to get a better idea of the terrain. Some off-roaders also use a spotter, a person who stands nearby and guides the driver in getting over the rocks.

A lot can go wrong when you're rock crawling. First, rocks can be sharp and jagged. The sidewalls of your tires are the weakest part, so you need to be careful where they come into contact with rocks to avoid puncturing them. Second, if you're moving too fast, the side-to-side rocking motion of your car as the tires move over rocks can build up and cause your vehicle to tip.

Knowing the angles on your car is very important in rock crawling. For each rock you encounter, you have to be able to judge whether your vehicle can clear it. This is yet another reason why speed isn't on your side when rock crawling: If you go too fast, you might not be able to accurately judge the obstacles in front of you. You also want to avoid straddling large rocks because there's always a chance they could damage the underside of your vehicle. The best option is to take a rock on with your tires instead of trying to pass over it. In other words, line up your tires with the rock so you'll drive over it. Don't expect the middle of your car to be able to clear it.

For more information about off-roading and other outdoor adventures, look over the links on the next page.

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Sources

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  • Quinnell, Cole. "Off-Roading 101 - How to Wheel in Rocks, Mud, Snow, and Sand." Off-Road Magazine. (October 28, 2009)http://www.off-roadweb.com/tech/0911or_off_roading_101_how_to_wheel_in_rocks_mud_sand_and_snow/index.html
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