Reading Topic: Reading Topic: Pros and Cons of FWD/RWD/etc
Wheels have a 'circle of grip', if you will. Their grip can be used to propel the car forward or laterally, but total grip is divided between these two directions. So if you are accellerating forward, the powered tires will not grip as well laterally as the ones not getting power.
If you throttle too hard in a turn in a FWD car, you'll end up going straighter than you are steering. This is understeer.
If you throttle too hard in a turn in a RWD car, you'll end up spinning further than you are steering. This is oversteer.
In ANY car, accelleration shifts weight to the rear of the car. The weight will help a RWD press its wheels to the pavement so they don't spin out. When a wheel spins, it looses its grip. In a FWD car, the wheels getting power become light, which takes away their grip. That's one big reason why it's impractical to have a powerful engine in a FWD car.
Combine these concepts: RWD will cause a car to oversteer under throttle, BUT under throttle, the rear of the car will grip better. Consequently, RWD cars can be driven harder through turns before they lose their grip.
RWD cars, because of the position of their transmission, typically have a better weight distribution. Ideally, you want as much of the car's weight centered between all the wheels to avoid weight shifts during corners. Less weight in the front of the car helps a car turn quickly since the front moves first. Rear-engine, RWD cars are fantastic.
It is harder to start spinning an AWD system than a simple two wheel layout. Simply, there are more, heavier parts to turn in a larger drivetrain. It requires proportionally more torque to get these parts to rotate. In general, the more (or larger) the axle and drive shafts, the more loss your drivetrain will have. This takes away from the engine power, so FWD engines are typically more efficient than RWD and especially AWD. Consequently, AWD gets poor gas mileage. FWD cars have torque steer because the transmission is not centered in the vehicle, making the drivetrain heavier on one side of the vehicle.
A good AWD vehicle will send its power only to the tires that are gripping by using advanced differentials. Differentials are what allow your tires to spin at different speeds than one another. Every car has one because in a turn, your inside tires do not turn as fast as your outside tires. A limited slip differential prevents this difference from becoming too great, preventing one-wheel spins. AWD cars have an added differential between the front and rear wheels. I don't think 4wd vehicles do this. Hence, if you ever spin all four tires in a 4wd vehicle, your car will drive like it's on ice- no traction in any wheel. This is also why there are no full-time 4WD cars.
The Mazda6 is pretty sweet. If you don't throttle through a turn, it'll oversteer. It's quite an amazing FWD car- unlike any other FWD car I've driven. With the '6, a little throttle in the turns will cause the car to do what's called a 'drift'. This is where all four wheels are just barely not gripping, and is the fastest possible way to take a turn.
Ask AJ about a 'waggle'.
Edit: the whole dang post was revised. If any of that is incorrect, tell me!
