RWD vs FWD advantages and disadvantages

Question

I want to know the advantages and disadvantages of rear wheel drive and front wheel drive cars I know that cars with FWD can't drift. Are there any other advantages or disadvantages?

Answer 1

To this question, there are quite a few perspectives to answer the question from. For example, advantages to the vehicle manufacturer of using transmission + engine types that are already developed and have passed emissions (Notice that manufacturers seem to use variants of the same engine for multiple vehicles) or are lower cost, may not include any advantages or disadvantages this causes the vehicle mechanics such as access to areas in the engine bay. The same can be said about the existence of different trade offs from the consumer's perspective.

To stay on topic, lets look at this from the driver's perspective and ignore the placement of the engine, relative the to the drive wheels[This will have a profound effect on the vehicle as well]. As was pointed out in your original question, the handling characteristics of a vehicle will be affected by which wheels are applying force to the road. To help visualize the differences, let us look at 3 different scenarios, vehicle is accelerating, vehicle is keeping constant speed, and vehicle is decelerating.

Vehicle Accelerating: While accelerating, the weight of your vehicle is is being shifted to the rear of the vehicle. This effectively reduces the maximum amount of traction available to the front wheels and increases the amount available to the rear wheels. Regardless of your vehicles drive type, there is less traction to change the direction of your car with the front wheels than there would be while maintaining constant velocity.

Front Drive - Because of the weight transfer to the rear, away from the drive wheels, less torque can be applied to the road before the wheels break and begin to spin. In theory this should decrease the the peak acceleration possible for a vehicle under hard acceleration.

Rear Drive - Because the weight is transferred to the rear, onto the drive wheels, more torque can be applied to the wheels before they break and begin to spin. This should increase the peak acceleration possible for a vehicle under hard acceleration. As an interesting sidenote to consider, in a rear drive car at in a the turn, the best way to keep the rear end from sliding out is to shift weight to the rear that requires the driver gently use the accelerator.

Vehicle Decelerating: The opposite can be said about weight transfer during deceleration. The weight should shift to the front of the vehicle, increasing the the maximum traction available to the front wheels. This will increase the amount of traction available to turn the vehicle using the front wheels.

Front Drive - With more traction available at the front, more torque can be applied before the drive wheels begin to slip. So while decelerating, a Front Drive car will be more able to punch the gas and keep traction on the drive wheels.

Rear Drive - With Less traction available in the rear, less torque can be applied to the drive wheels before they begin to slip. This slipping of the rear wheels outwards is often called oversteer.

Vehicle at Constant Velocity: While at constant velocity, the weight of the car should be at it equilibrium state and the base amount of traction should be available at all 4 wheels. Once additional power is applied, or taken away, one of the other two states apply.

This is a very simple explanation that only covers a portion of what could be with this question. Here are a few other questions that might be good to consider. I am sure that others here can add additional good questions to ask as well.

What are the trade offs of each type of engine layout? http://en.wikipedia.org/wiki/Automobile_layout

How does Load Transfer affect vehicle performance?

Answer 2

Both methods of drive have their advantages.

FWD is generally cheaper to build, and gives more space inside the vehicle (as there is no need for a transmission tunnel). It is also generally easier for a less skilled driver to control - Most ordinary people don't want to need to learn how to drift or control a slide. On the other hand, smaller FWD cars can be at risk of snap lift-off oversteer...

RWD on the other hand is simpler, and can be argued to give better balance and control near the limit, as the front wheels aren't being asked to both drive and steer, which puts more demands on the limited amount of grip available.

4WD has more grip than either, and is invaluable for getting out of slippery conditions, but is more complicated and expensive to make, and tends to result in worse fuel economy.