The Physics of Off-Roading
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 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 , 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 yourcar 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 breakover angle . If you 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 .
MEASURING YOUR ANGLES THE CARDINAL RULE OF OFF-ROADING
You don ' t need a protractor to measure your car ' s angles . If you don ' t want to risk damaging your car through trial and error , try this : Take a long , straight object such as a yardstick , broomstick or board , and place one end where the front of your front tire touches the ground . Lift the other end up until it hits the lowest point of the front of your car , usually the bumper . The angle of the object is your approach angle . You should never try to climb a hill steeper than this , or attempt to go over a rock higher than the point at which the board makes contact with your bumper .
By nature , the possibility of getting stuck while off-roading looms large . No matter how prepared you are or how many times you ' ve driven through an area , the unexpected can always happen . This brings us to the cardinal rule of off-roading : Never go alone . You never know when you ' ll need someone to tow your vehicle out of the mud .
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