Weight Transfer under Braking and Acceleration

One of the key skills that all good drivers have is the ability to control the weight of their car. We are not talking about removing or adding actual weight to the car, but the transfer of the car’s weight as it accelerates, decelerates, or turns.

The Water Bottle Metaphor

A common metaphor for weight transfer in a vehicle is to visualize a half-filled bottle of water on its side. Here, the bottle represents the car and the water represents the distribution of weight in the car.

Constant velocity - balanced distribution

When accelerating - front gets lighter, rear gets heavier

When braking - front gets heavier, rear gets lighter

When the car is not moving or moving at constant speed, the water line is flat, which indicates no inputs to the car. The weight is evenly distributed, making the car easy to control.

When the car accelerates, we can imagine the bottle tilting backwards, with water now rushing towards the back. The weight shifts to the rear of the car, resulting in less traction on the front wheels (harder to steer) and more traction on the rear wheels (easier to accelerate for a RWD car). In this scenario, the car is more prone to understeer as there is less grip for the front tires to turn.

When the car brakes, the front of the bottle fills with water. The front wheels get more grip and the rear wheels get less, which makes it is easier to steer and harder for RWD cars to put down power. When weight shifts forward, the car is more prone to oversteer as there is less grip on the rear tires.

Still water, high speeds

The point of the water bottle metaphor outside of visualizing weight transfer is that you should minimize abrupt movement of the "water". Weight shifting destabilizes your car and makes it less predictable, which is the antithesis to going fast. As you become more advanced as a driver, being able to manipulate weight and balance smoothly is a key skill that you will develop.

Your gas and brake pedals do more than just slow down or speed up your car. They control the weight distribution and physics of your car as you drive around the track. Smooth inputs may seem boring on videos, but it’s the secret to becoming a better driver.

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