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Wednesday, December 19, 2007
Four-Wheel Drive Basics
What’s four-wheel-drive? It's where the engine drives all four wheels either part of the time or all of the time. Most vehicles are two-wheel drive, or in other words, either the front or back wheels are driven by the engine.
Four-wheel drive (4WD) is an option on many SUVs, and there are pros and cons to this expensive and complicated feature.
The extra cost of 4WD differs by model because some systems are more complex than others. Certain SUVs, like the BMW X3 and X5, Mercedes-Benz M-Class and Honda Pilot are available only with 4WD, so your options will narrow if you decide that you don't want 4WD.
The reason these systems are now so popular is the added traction, the biggest advantage to four-wheel drive. The first 4WD systems were designed for crossing rough terrain with boulders, mud and steep landscape. Newer, electronically controlled 4WD systems enhance traction on asphalt and pavement. The added traction offered by these systems can be especially useful on slippery roads (in rain, snow, dirt, gravel and mud), because it reduces the danger of losing control of the vehicle should one or all of the wheels lose grip.
When towing and hauling heavy loads, four-wheel drive can also help. The additional weight of a large payload or trailer can make a vehicle less stable and create tractions problems, which 4WD drive can correct.
4WD becomes more justifiable if the winters are harsh where you live. But two-wheel drive will be fine for most drivers, particularly now that greater numbers of vehicles have electronic traction control and stability control as standard or optional equipment.
A two-wheel-drive vehicle (whether front- or rear-driven) will perform safely and securely even in all but the harshest of snowy conditions, in snow with the proper snow tires mounted on all four wheels. Comparison tests performed in the snow by automotive magazines have shown that a 2WD drive vehicle with snow tires on all four wheels will outperform a 4WD vehicle with regular tires.
The added assurance of having four-wheel drive can be largely psychological. The instances in which most drivers who don't travel off-road actually benefit from having 4WD are relatively few, unless winters are harsh where they live.
Along with motor vehicle safety, driver education helps ensure the safety of young Americans. Whether they're getting their Learner's Permit or a Motorcycle License, America's Driver License Headquarters is TestQuestionsandAnswers.com.