Rear-wheel drive

From Wikipedia, the free encyclopedia

This article or section does not cite its references or sources.
You can help Wikipedia by introducing appropriate citations. This article has been tagged since September 2006.

Rear-wheel drive (or RWD for short) was a common engine/transmission layout used in automobiles throughout the 20th century. RWD typically places the engine in the front of the vehicle, but the front mid-engine, rear mid-engine and rear engine layouts are also used.

The vast majority of rear wheel drive vehicles use a longitudinally-mounted engine in the front of the vehicle, driving the rear wheels via a driveshaft linked via a differential between the rear axles. Some FR layout vehicles place the transmission at the rear, though most attach it to the engine at the front.

Rear wheel drive has fallen out of favor in passenger cars since the 1980s^{[citation needed]}, due in part to higher manufacturing costs, and because on slippery roads and snow, front wheel drive is safer. However, some automobile brands, including Mercedes-Benz, BMW and Porsche continue to use rear wheel drive platforms.

It still sees heavy use in taxi and police fleets in some countries, due to cheaper maintenance, and in the case of police fleets, better handling performance on dry surface.^{[citation needed]}

1 Advantages
2 Disadvantages
3 Current or recent rear wheel drive cars to 2006
4 External links

[edit] Advantages

Better handling in dry conditions - accelerating force is applied to the rear wheels, on which the down force increases, due to load transfer in acceleration, making the rear tires better able to take simultaneous acceleration and curving than the front tires.

Less costly and easier maintenance - Rear wheel drive is mechanically simpler and typically does not involve packing as many parts into as small a space as does front wheel drive, thus requiring less disassembly or specialized tools in order to replace parts.

No torque steer.

Even weight distribution - The division of weight between the front and rear wheels has a significant impact on a car's handling, and it is much easier to get a 50/50 weight distribution in a rear wheel drive car than in a front wheel drive car, as more of the engine can lie between the front and rear wheels (in the case of a mid engine layout, the entire engine), and the transmission is moved much farther back.

Steering radius - As no complicated drive shaft joints are required at the front wheels, it is possible to turn them further than would be possible using front wheel drive, resulting in a smaller steering radius.

Towing - Rear wheel drive puts the wheels which are pulling the load closer to the point where a trailer articulates, helping steering, especially for large loads.

Weight transfer during acceleration - During heavy acceleration, the front end rises, and more weight is placed on the rear, or driving wheels.

Enjoyment factor - As RWD cars are commonly associated with drifting, it is much easier, as power can be applied to keep the drift going--more power aids the drift. Front wheel drive and four wheel drive cars may also drift, but only with much more difficulty. When front wheel drive cars drift, the driver usually pulls on the hand brake in order for the back wheels to stop and thus skid.

[edit] Disadvantages

On snow and ice, rear wheel drive is dangerous because once the car has started skidding, the car can often spin several laps before it regains traction. With front wheel drive, the driver can control the skidding by steering, throttling and move the rear wheels by pulling the hand brake. With rear wheel drive the only thing the driver can do is disengage the clutch and wait for the car to stop spinning.

Decreased interior space - In a passenger car, rear wheel drive means: Less front leg room as the transmission tunnel takes up a lot of space between the driver and front passenger, less leg room for center rear passengers (due to the tunnel needed for the drive shaft), and sometimes less trunk space (since there is also more hardware that must be placed underneath the trunk). There are some exceptions to this as rear engine designs do not take away interior space. (See Porsche 911, and Volkswagen Beetle)

Increased weight - The components of a rear wheel drive vehicle's power train are less complex, but they are larger. The driveshaft adds weight. The transmission is probably heavier. There is extra sheet metal to form the transmission tunnel. There is a rear axle or rear half-shafts. A rear wheel drive car will weigh slightly more than a comparable front wheel drive car (but less than four wheel drive).

Oversteer (also deliberately used in drifting) and the related problem of fishtailing.

[edit] Current or recent rear wheel drive cars to 2006

While the popularity of rear wheel drive has declined, it is still relatively prevalent, and has been making something of a resurgence. Here is list of current or recent rear wheel drive vehicles. See also Category:Rear wheel drive vehicles.