Few drivers ever ponder the physics associated with the drivetrain layout of their car, but those who do will grow to appreciate the importance of weight transfer and weight distribution. For race car drivers and automotive engineers the relationship between weight and traction is elementary, and it predicates why most racers prefer rear wheel drive (RWD) cars and most engineers turn to a RWD layout when attempting to build the fastest race car possible.
Consider that when a car is sitting at a standstill, the weight distribution between the front and rear axle is determined largely by engine and drivetrain layout. For instance, in a front-engine, front wheel drive car approximately 60 percent of the weight will rest upon the front wheels while the balance of 40 percent will rest upon the rear wheels. When braking hard for a corner on the racetrack or to avoid a collision on the road, dynamic weight transfer will add even more weight to the front axle while subtracting weight from the rear axle.
Weight and grip are correlated such that increased weight on a tire results in increased grip (try pushing an eraser along your desk with one finger, then try pushing down hard on the eraser while attempting to slide it across the surface). Therefore, if less weight rests on the rear wheels and then during braking more weight is subtracted from the rear wheels, little traction will be available to the rear tires while generous helpings of grip will be available to the front tires. This imbalance of traction can lead to a loss of control as the rear of the car feels ‘nervous’ and has a tendency to slide out, causing a spin.
Now consider the advantage a RWD car has during hard braking due to its inherently better balanced chassis (most RWD cars maintain a 50:50 weight distribution). With more weight resting on the rear wheels, more grip will be available to the rear tires during hard braking, thus the vehicle is more likely to remain stable, eschewing the tendency to spin.
The superior dynamics of RWD doesn’t stop there. When accelerating, weight transfer shifts weight onto the rear wheels, increasing grip on the tires responsible for acceleration. This bestows RWD sports cars with tenacious grip while exiting corners.
Finally, there’s the matter of steering feel. Both FWD and AWD vehicles send engine torque through the front wheels. This creates “torque steer,” wherein the steering is distorted by torque sent through the front wheels, tugging at your steering wheel. A RWD car is capable of conveying clear, undistorted, detailed sensation from the front tires to the driver’s hands, allowing the driver to accurately judge front axle grip.
Perhaps the biggest argument for RWD lies in the smile it often lands on your face while enjoying a spirited drive. The natural balance of the car feels good beneath you, and if you’re prone to such antics, nothing quite satisfies your automotive appetite like a lurid power-slide through a wide-open corner.