Even all-wheel-drive crossovers, whose transmission has an electromagnetic or hydraulic clutch in the rear axle, have the main front axle, and the rear one only helps “push” the car during slippage. Motorists like such a scheme and give it their preference. However, on sports cars and premium models, front-wheel drive is considered unacceptable. Until now, classic layouts with a leading rear axle have been used there. A powerful Lamborghini or Mercedes-Benz is impossible to imagine as front-wheel drive. Is there a sense in it or it is simply a tribute to traditions?
Layout secrets
The classic layout is a separate market niche today. Mercedes-Benz, BMW, Porsche, Bentley, Lamborghini and other automakers are loyal to rear-wheel drive, which has become part of the image of premium and luxury cars. A powerful, comfortable and solid car should also have a longitudinal arrangement of the motor and transmission. The fact is that a large and powerful motor can be used in the car only if it is installed longitudinally. This is the only way to install a long eight-cylinder V-shaped unit under the hood.
To free up space, engineers are trying to increase the engine compartment, move the wheel axle forward and move the cab back a bit. The transmission is also installed. Behind the engine there is a gearbox, which is installed in the center of the body and connected to the rear axle through a cardan shaft. As a result, the weight is evenly distributed across the body, which has a positive effect on steerability. The rear gearbox and fuel tank balance the engine and box stretched along the body. Engineers on classic cars manage to achieve an even weight distribution along the axles, and the center of mass of the car is at the level of the hips of the people sitting in it. It’s the ideal choice, because cars are less prone to skidding, and can go around tight corners at higher speeds.
In general, the classic scheme of car layout with rear-wheel drive can work with engines of unlimited power, which is what the developers of sports cars like. When accelerating, the rear drive wheels are loaded much more heavily than the front ones. The car piles on them with all its weight, pressing them to the ground, and the higher acceleration, the stronger the hook of the leading wheels. This is why sports cars in drag racing are exclusively rear-wheel drive. For the same reason, a rear-wheel drive car is more confident going uphill than a front-wheel drive car.
Why is front-wheel drive limited in terms of power?
Test of the fastest 911 – what six letters did to the Porsche coupe
The front-wheel drive car has a different layout. On compact models, the powertrain and transmission stand transversely under the hood and are angled vertically. The right and left output shafts that go to the wheels are unequal in length. As they rotate, they create parasitic moments that pull the car sideways during acceleration or braking. To compensate for these peculiarities, a number of technical devices have to be implemented.
Besides, it is considered that the front-wheel drive cannot cope with power over 250 hp. It is impossible to insert a big motor transversely into such car, and also during acceleration the torque lifts the nose of front-wheel drive car and shifts its weight backwards. Due to forces of inertia, the body unloads drive wheels at startup, and that is why they lose load and slip under the traction.
The designers try to compensate for this peculiarity of the front-wheel-drive scheme by placing the transverse engine and the box in front of the drive axle. However, this is not always enough. The motors with power more than 250 hp will quickly lead the wheels to slipping. That is why you can forget about powerful motors.
The best maneuverability
Classic premium cars are more maneuverable. The front wheels are not limited by the angle of rotation of the CV joints, as in front-wheel drive cars. Therefore, in a tight yard or on a narrow road, the rear-wheel drive makes it easier to turn around.