Advantages & Disadvantages of Front And Rear Wheel Drive

Advantages & Disadvantages of Front Wheel Drive

 

Advantages of Front Wheel Drive:

1.    Interior space: Since the powertrain is a single unit contained in the engine compartment of the vehicle, there is no need to devote interior space for a driveshaft tunnel or rear differential, increasing the volume available for passengers and cargo.

2.    Cost: Fewer components overall

3.    Weight: Fewer components mean lower weight

4.    Fuel economy: Lower weight means better gasoline mileage

5.    Improved drivetrain efficiency: the direct connection between engine and transaxle reduce the mass and mechanical inertia of the drivetrain compared to a rear-wheel-drive vehicle with a similar engine and transmission, allowing greater fuel economy.

6.    Assembly efficiency: the powertrain can be often be assembled and installed as a unit, which allows more efficient production.

7.    Slippery-surface traction: placing the mass of the drivetrain over the driven wheels improves traction on wet, snowy, or icy surfaces. Although heavy cargo can be beneficial for traction on rear-wheel-drive pickup trucks.

8.    Predictable handling characteristics: front-wheel-drive cars, with front weight bias, tend to understeer at the limit, which is commonly believed to be easier for average drivers to correct than terminal oversteer, and less prone to result in fishtailing or a spin.

9.    Better crosswind stability.

10. Tactile feedback via the steering wheel informing the driver if a wheel is slipping.

11. Front-wheel drive allows the use of left-foot braking as a driving technique.

 

Disadvantages of Front Wheel Drive:

1.    The center of gravity of the vehicle is typically farther forward than a comparable rear-wheel-drive layout. In front-wheel-drive cars, the front axle typically supports around 2/3rd of the weight of the car (quite far off the "ideal" 50/50 weight distribution). This is a contributing factor in the tendency of front wheel drive cars to understeer.

2.    Torque steer can be a problem on front-wheel-drive cars with higher torque engines ( > 210 N·m ) and transverse layout. This is the name given to the tendency for some front-wheel-drive cars to pull to the left or right under hard acceleration. It is a result of the offset between the point about which the wheel steers (which falls at a point which is aligned with the points at which the wheel is connected to the steering mechanisms) and the centroid of its contact patch. The tractive force acts through the centroid of the contact patch, and the offset of the steering point means that a turning moment about the axis of steering is generated. In an ideal situation, the left and right wheels would generate equal and opposite moments, canceling each other out, however in reality this is less likely to happen. Torque steer is often incorrectly attributed to differing rates of twist along the lengths of unequal front driveshafts. However, Centre-point steering geometry can be incorporated in the design to avoid torque steer. This is how the powerful Citroen SM front-wheel-drive car avoided the problem.

3.    Lack of weight shifting will limit the acceleration of a front-wheel-drive vehicle. In a rear-wheel-drive car the weight shifts back during acceleration giving more traction to the driving wheels. This is the main reason why nearly all racing cars are rear-wheel drive. However, since front-wheel cars have the weight of the engine over the driving wheels the problem only applies in extreme conditions.

4.    In some towing situations, front-wheel-drive cars can be at a traction disadvantage since there will be less weight on the driving wheels. Because of this, the weight that the vehicle is rated to safely tow is likely to be less than that of a rear-wheel drive or four-wheel drive vehicle of the same size and power.

5.    Due to geometry and packaging constraints, the CV joints (constant-velocity joints) attached to the wheel hub have a tendency to wear out much earlier than their rear-wheel drive counterparts? The significantly shorter drive axles on a front-wheel-drive car cause the joint to flex through a much wider degree of motion, compounded by additional stress and angles of steering, while the CV joints of a rear-wheel-drive car regularly see angles and wear of less than half that of front-wheel drive vehicles.

6.    The driveshafts may limit the amount by which the front wheels can turn, thus it may increase the turning circle of a front-wheel-drive car compared to a rear-wheel-drive one with the same wheelbase.

7.    In low traction conditions (i.e.: ice or gravel) the front (Drive) Wheels lose traction first making steering ineffective.

Advantages & Disadvantages of Rear Wheel Drive

 

Advantages of Rear Wheel Drive:

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

2.    More predictable steering in low traction conditions (i.e.: ice or gravel) because the steering wheels maintain traction and the ability to affect the motion of the vehicle even if the drive wheels are slipping.

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

4.    No torque steer.

5.    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.

6.    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 the front-wheel drive, resulting in a smaller steering radius.

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

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

9.    Drifting - Drifting is a controlled skid, where the rear wheels break free from the pavement as they spin, allowing the rear end of the car to move freely left and right. This is of course easier to do on slippery surfaces. Severe damage and wear to tires and mechanical components can result from drifting on dry asphalt. Drifting can be used to help in cornering quickly, or in turning the car around in a very small space. Many enthusiasts make a sport of drifting and will drift just for the sake of drifting. Drifting requires a great deal of skill, and is not recommended for most drivers. It should be mentioned that 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 emergency brake in order for the back wheels to stop and thus skid. This technique is also used for 'long' drifts, where the turn is accomplished by pulling the e-brake while turning the steering wheel to the direction the driver desires. With drifting, there is also the importance of 'counter-steering' - where while temporarily out of control, the driver regains it by turning the wheel in the opposite direction and thus preparing for the next turn or straight-away.

 

Disadvantages of Rear Wheel Drive-

1.    More difficult to master - While the handling characteristics of the rear-wheel drive may be more fun for some drivers, for others having rear-wheel drive is less intuitive. The unique driving dynamics of rear-wheel-drive typically do not create a problem when used on vehicles that also offer electronic stability control and traction control.

2.    Decreased interior space - This isn't an issue in a vehicle with a ladder frame like a pickup truck, where the space used by the driveline is unusable for passengers or cargo. But in a passenger car, rear-wheel drive means Less front legroom (the transmission tunnel takes up a lot of space between the driver and front passenger), less legroom 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).

3.    Increased weight - The driveshaft, which connects the engine at the front to the drive axle in the back, adds weight. There is extra sheet metal to form the transmission tunnel. A rear-wheel-drive car will weigh slightly more than a comparable front-wheel-drive car, but less than four-wheel drive.

4.    Higher purchase price - Due to the added cost of materials, rear-wheel drive is typically slightly more expensive to purchase than a comparable front-wheel-drive vehicle. This might also be explained by production volumes, however. Rear-drive is typically the platform for luxury performance vehicles, which makes read drive appear to be more expensive. In reality, even luxury performance front-drive vehicles are more expensive than average.

5.    More difficult handling on low grip surfaces (wet road, ice, snow, gravel...) as the car is pushed rather than pulled. In modern rear-drive cars, this disadvantage is offset by electronic stability control and traction control.