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Aug 22, 2018

Front Wheel Drive (FWD) vs. Rear Wheel Drive (RWD).

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Edited: Aug 22, 2018

The numbers suggest that two-wheel drive just isn't enough for many consumers.

Still, most passenger cars sold in the Indian market today use a two-wheel-drive system in which the entire drive package — engine, transmission, differential and the wheels that are driven by the engine — are all in the front of the vehicle.

 

It is called front-wheel drive (FWD) and has become ubiquitous in cars since the late 1970s.

Trucks as well as many SUVs and some cars still use rear-wheel-drive (RWD) systems, in which a long driveshaft transmits power from the engine in the front of the vehicle to the driven wheels at the back. A differential is used to let the power from the driveshaft make a 90-degree turn so it can get to the to the wheels.

 

With all those choices, what's right for you?

It all comes down to what you need most from your vehicle in terms of passenger and cargo capabilities as well as what kinds of terrain and weather conditions you deal with on a regular basis.

A low-slung sports car with rear-wheel drive is not a good choice if you live at the top of a steep hill accessible via a rutted dirt road that usually is buried under ice and snow all winter and slick with mud all spring. Nor is a raised four-wheel-drive utility vehicle with huge knobby tires ideal for the driver whose daily commute via a nicely paved highway is from a suburban house to a high-rise office in a metropolitan downtown area.

Rear wheel drive vs. Front wheel drive Compared to rear-wheel drive, front-wheel drive reduces weight and production cost, improves fuel economy, and typically delivers better traction. That's because the weight of the engine and transmission is directly over the driven wheels. Rear-wheel drive offers better initial acceleration than does FWD when a quick start is of the essence. That's because weight is transferred to the rear of the car upon accelerating, thus boosting traction. RWD also permits expert drivers to use various techniques to slide the rear end around corners, which is a skill most useful in racing. Additionally, by keeping part of the drivetrain in back, a rear-wheel-drive car usually has weight distribution closer to the optimal 50 percent front and 50 percent rear than can be achieved with a FWD system. Equal weight distribution improves a vehicle's overall balance and handling.

Ups and Downs of FWD In two-wheel-drive trucks, RWD is essential because the back of the truck is so light that putting the entire drive system up front would make an empty pickup nearly impossible to drive. The rear wheels would almost be floating and would easily lose contact with the surface on even moderately bumpy roads. Conversely, adding load in the rear of a RWD truck or SUV that's hauling cargo or a towing a trailer or boat improves traction. Having the driven wheels close to the point where the trailer is connected to the vehicle via an articulated hitch also helps with steering while towing. Front-wheel-drive systems are less complex and thus cheaper to make than other drivetrain systems, so economics has played a role in their growing use. But fuel efficiency is the main reason most cars today are FWD models. Keeping the motor's weight directly over the driven wheels also improves acceleration and traction on roads made slippery with things such as water, ice, sand, gravel or snow. Finally, using the front wheels to pull the car around corners also helps reduce a common problem in rear-wheel-drive vehicles: loss of traction, or "fishtailing," when entering a curve too fast

The Downside of Front-Wheel Drive Despite its practical advantages, front-wheel drive has several performance disadvantages. Some exhibit a characteristic called torque steer, in which unequal power application to one of the front wheels causes the vehicle to pull to one side or another under heavy acceleration. Additionally, a front-driver's turning radius can often be greater than the same vehicle with RWD. That's because cramming all that powertrain and drivetrain equipment under the hood doesn't leave enough room for the front wheels to be turned as sharply as in a rear-wheel-drive application. FWD systems also tend to wear out faster than the less complex RWD systems. Further, the lifespan of front tires can be compromised because so much weight is placed on them and they have to handle all of the acceleration and steering forces as well as much of the braking.

Ups and Downs of RWD Everything about front-wheel drive is reversed for vehicles with rear-wheel drive. Performance goes up: When you punch the accelerator pedal in a rear-wheel-drive vehicle, the weight transfers to the rear end, just where you want it during acceleration. As a result, the front wheels focus on directing the vehicle. You can also "steer" a rear-wheel-drive car with the gas pedal by applying power and sliding the rear end while in a corner, although this is a tactic best reserved for expert drivers on racetracks.

This performance advantage doesn't necessarily make rear-wheel drive the better configuration. RWD has its own disadvantages. RWD cars require a driveshaft, and to accommodate it, they have that space-robbing interior hump down the middle of the passenger cabin. They also need a rear differential to make the 90-degree turn necessary to transfer engine power from driveshaft to the rear wheels. These components add extra cost and weight to a vehicle while robbing horsepower and making RWD cars generally less fuel-efficient than front-wheel-drive vehicles.

Rear-wheel drive also is more challenging in inclement weather. Without the aid of traction control, a RWD car can more easily end up on somebody's front lawn or stuck in a ditch. Fortunately, traction control is standard on most cars and trucks today.

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