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. Out of these four available options, I am going to pick only two: front wheel drive & rear wheel drive. Each has its advantages, and no single layout is best for all situations.

It will help to understand a device known as the differential. If you imagine a pair of wheels on an axle going around a turn—and a turn, for this discussion, is anything that is not absolutely straight—then it becomes apparent that the wheel on the outside of the turn must travel a greater distance than the wheel on the inside. Therefore, it must also rotate faster. To allow this “differential” rate of speed between the wheel on the inside of the turn and the wheel on the outside, there is a device called, appropriately enough, a differential. It is comprised of a set of gears, arranged so that power will be delivered to both wheels, while still allowing them to rotate at different speeds if need be. Another characteristic of a common, “open” differential is that it will deliver power equally to both wheels as long as they both have equal traction. But, if one wheel is easier to turn than the other—as, for example, if one wheel is on ice—the open differential will send the power to that wheel which is easiest to turn, causing that wheel to spin and resulting in the vehicle not having enough traction to keep moving. Thus, there are a variety of systems, under the term of “limited-slip differentials,” which “limit” the “slip” that might occur if one wheel is on a slippery surface. These limited-slip differentials are popular with people who must drive in conditions in which they frequently encounter poor traction, such as ice or snow.

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.

With those things in mind, let’s discuss some characteristics of front wheel drive and rear wheel drive layouts.

Rear wheel drive:

rear wheel drive

With rear wheel drive the rear wheels drive the vehicle. For decades, rear wheel drive was the system of choice, primarily because it is easy to manufacture, simple, inherently robust and reliable. The typical rear wheel drive layout consisted of an engine in front, connected to a transmission, then the power went through a driveshaft to the rear-axle gears and then the rear wheels. Almost all trucks—except a few light-duty models—have been rear wheel drive. If you look under the rear of a typical pickup truck you will see the rear axle housing, which has a big lump, or bulge, in the center, roughly the size of a pumpkin or basketball. Inside that bulge will be found the ring-and-pinion gears—which transfer power from the driveshaft to the wheels, provide the appropriate gear ratio and also allow the power to make the right-angle turn from the driveshaft to the wheels—and the gears and assembly that make up the differential. By the way, the ring-and-pinion gears—also known as the final drive—are not the differential, and you can have one without the other.

With rear wheel drive the rear wheels move the vehicle and the fronts provide steering. Thus, there is somewhat of a division of labor. The advantages of rear wheel drive are based upon the application. For trucks and heavy-duty vehicles, rear wheel drive offers rugged durability and, as the load is increased, the traction also increases, because that load pushes down on the driving wheels. For passenger cars, rear wheel drive offers the capability to deal more effectively with higher engine outputs and higher vehicle weights. Luxury cars, for example, tend to have rear wheel drive. All true sports cars have rear wheel drive, and all purpose-built race cars, such as those raced in Formula One Grand Prix racing, or in NASCAR, have rear wheel drive. For performance applications, a primary advantage of rear wheel drive is that weight transfer causes traction to be increased with acceleration—the more acceleration, the more weight transferred to the rear wheels and the more available traction, all of which enhances acceleration.

A rear wheel drive vehicle also has a more equitable balance of the vehicle’s weight front-to-rear, so each tire carries a more equal share of the load, which leads to improved cornering response and higher potential cornering limits. Finally, a rear wheel drive vehicle can offer potentially superior braking performance because, when the brakes are applied, the weight is more equitably allotted among all four wheels.

By the way, in case you’re interested, the ideal weight distribution, as it is known, for maximum performance—as with a pure race car—is to be rear wheel drive and tail-heavy. This helps acceleration, because there is more weight on the rear, driving wheels, and also helps braking because, under the extreme weight transfer that occurs during braking in racing conditions, the vehicle’s weight then becomes more evenly distributed among all four wheels, so each of the four wheels can make a maximum contribution to stopping power. A high-powered, pure race car, such as those that race at Indianapolis or in Formula One, will have roughly 35 percent of its total weight on the front wheels and 65 percent on the rear wheels.

Front wheel drive:

front wheel drive

With front wheel drive the engine, transmission, final drive gears and differential are in a single unit and drive the front wheels. Most modern sedans, and particularly those in the medium and lower price ranges, or with more moderate power levels, have front wheel drive. There are two basic reasons for front wheel drive: better fuel economy and enhanced space efficiency. By combining the entire powertrain into one unit, the remainder of the vehicle can be made much lighter in weight. It can also be made roomier inside for passengers and cargo, because the engine, transmission and other powertrain components intrude less into that available space. Therefore, all minivans are front wheel drive; without front wheel drive they simply could not offer the space efficiency that makes them so popular.

Front wheel drive has some operational advantages, as well. With all that weight concentrated over the driving wheels, it offers very good traction on slippery surfaces at relatively lower speeds. Thus, front wheel drive cars perform very well in snowy conditions, or on ice. People who live in places with frequent bad weather understand these benefits of front wheel drive.

A typical front wheel drive car will carry about 65 percent of its weight on the front wheels, so a major disadvantage of front wheel drive is related to weight transfer. Under harder acceleration, weight is transferred off the driving wheels, so traction is reduced. Under harder braking, even more weight is transferred to the front wheels, so they have to do the vast majority of the work. Therefore, on a front wheel drive car, the front tires and the front brakes wear out much faster than those on the rear. But, on the flip side, a front wheel drive car, with all that weight on the front, will generally be very good at what engineers call “directional stability,” or the tendency to keep going straight. This can tend to make a front wheel drive car very stable at highway speeds during crosswinds, for example.

It is true that there are several front wheel drive cars which offer quite exemplary levels of performance but, in absolute terms, and assuming equal levels of power, weight, expense and engineering sophistication, a front wheel drive car will never match the maximum performance capability of a rear wheel drive car.

Which should you pick? 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. You have to decide what’s best for the driving you do. let’s now head back to our facebook page for more technical discussion on the topic.