ALL WHEEL DRIVE
All Wheel Drive - Do You Need It?
All Wheel Drive - Do You Need It?
Many drivers would never choose a vehicle without all-wheel drive (AWD), yet most of them will never take it off road. With today's traction controls and electronic systems, is AWD really necessary, especially in California? Let’s take a closer look.
Many car buyers are confused by the matter of which wheels actually drive the vehicle, and which is best for their particular needs. There are four main choices: front-wheel drive, rear-wheel drive, four-wheel drive or all-wheel drive. Each has its advantages, and no single layout is best for all situations.
Most passenger vehicles on the road today use front-wheel drive (FWD), where the engine’s power is routed to the front wheels. In fact, all but a handful of SUVs are primarily front-wheel drive vehicles, with additional components that send some power to the rear wheels as the need arises.
Front-wheel drive designs are cheaper to manufacture and more space-efficient than rear-drive systems. Plus, FWD has the added advantage of better traction while climbing hills because the engine’s weight is poised over the front wheels. From a packaging standpoint, front-drive also precludes the need for a space-robbing driveline hump running down the middle of the cabin floor.
Rear-wheel drive (RWD) is commonly found on pickups and old-school truck-based SUVs, along with sports cars and high-performance and luxury sedans. For trucks, RWD allows the use of bulky, heavy-duty components, and it provides better traction with a hefty load.
On a performance car, rear-wheel-drive improves handling by balancing the car’s weight more evenly front to rear. And because the front wheels don’t have to do double duty—both driving and steering—designers can optimize the suspension for handling prowess. However, RWD provides less traction on slippery roads. These days, most high-end cars offer all-wheel drive either standard or as an option.
For most SUVs the base model 2WD vehicles are actually 1WD, a single wheel transferring power from the differential to the road. If you opt for a 2WD SUV, be sure the manufacturer offers the option of a limited slip rear differential. This system allows power to be transferred to either rear wheel. A 2WD SUV so equipped can handle dirt roads and gravel washes with complete confidence. There are also a number of SUVs whose 2WD power is delivered via the front wheels. This arrangement offers superior traction in either rain or snow.
A 2WD SUV is also lighter (no extra hardware to drive all four wheels) and therefore earns a slightly better EPA fuel mileage rating. Maintenance costs should be lower over the life of the vehicle, again fewer moving parts to worry about. Most importantly, depending on your age and gender, insurance costs are generally lower for a 2WD SUV.
As the name implies, all-wheel drive (AWD) feeds power to each corner. Depending on the system (designs vary), AWD can provide maximum forward traction during acceleration. It is especially helpful in sloppy road conditions and when driving over moderate off-road terrain. It can help get you going and keep you moving through mud, sand, and other loose surfaces. Most AWD systems deliver power primarily to one set of wheels, front or rear. When slippage is detected at one axle, power is diverted to the other axle, in hopes of finding more traction there.
Drivers who opt for 4WD have numerous variations from which to choose. One of the most commonly used 4WD systems employs a simple high/low transfer case which routes power equally to the front and rear differentials. When engaged, both front and rear wheels turn at the same rate of speed. This system is called part-time 4WD and is intended only for use off road. Because a vehicle's wheels rotate at different speeds when turning a corner, part- time 4WD cannot be engaged on dry pavement (which doesn't allow the wheels to slip) or at speeds greater than 40 mph (taking a curve at this speed will damage the gearbox).
For rain and very light snow, 2WD will likely work fine, and for most vehicles, front-wheel drive is the preferred setup. (For performance cars, RWD is preferred, but AWD, if available, can increase traction. AWD is fine for most normal snow conditions or for light-duty, off-pavement excursions. If you'll be driving in severe snow or true off-road situations, or if you're interested in pursuing off-roading as a hobby, you should opt for a vehicle with 4WD and lots of ground clearance. Keep in mind that both AWD and 4WD systems add considerable weight to a vehicle, compromising fuel economy.
Other Factors To Consider
All passenger vehicles sold in the U.S. starting with the 2012 model year come equipped with electronic stability control, which along with traction control, significantly improves road-holding capabilities regardless of the drive wheels. Even so, we have found there are distinct differences in the driving, and traction, characteristics among drive types.
Another thing to consider is what engineers call weight transfer. As a vehicle accelerates forward, its weight is transferred to the rear, onto the rear wheels. As it stops, its weight is transferred to the front, onto the front wheels. This is why any vehicle "squats" at the rear when the driver steps on the accelerator, or "dives" at the front when the driver steps on the brakes.
Is all-wheel drive for you? If you live in an area frequently hit by harsh winter storms and paralyzed by slick streets, the answer is probably yes. But for those who don't have to deal with such difficult climates, like most of California, you might not need it as much as you think -- especially since it costs more to buy and lowers your gas mileage
For most people, most of the time, front-wheel drive, with its benefits of fuel economy, space efficiency and good traction in slippery conditions, is the best choice. For ultimate performance in decent weather, it's rear-wheel drive. For the serious off-roader or the tough work in really bad weather, it's four-wheel drive. And for the all-time, all-around, all-weather maximum traction, it's all-wheel drive. You have to decide what's best for the driving you do.
The benefit of all-wheel drive is that it is, typically, "on" all the time, so the driver doesn't have to do anything, doesn't have to move a lever or engage the transfer case, to make it work. If the vehicle is in motion, the system is working. However, for very heavy-duty off-road situations, all-wheel drive doesn't quite match pure four-wheel drive. To deal with this, many modern all-wheel drive systems have the capability to be locked into a pure, four-wheel drive mode, when the going gets really tough.
Bottom line, look at your driving situation, and associated costs with the choices, but driving carefully and safely is still of utmost importance. So drive safely and have fun!
Tags: All wheel drive, AWD, 4 Wheel drive, 4WD, 2WD, front wheel drive, FWD, rear wheel drive, traction, SUV, traction control, electronic stability control