Weight Transfer

The Relationship Between Steering and Pedals

One of the most important dynamics we need to learn about car racing is the strong relationship and interference between the steering and the pedals. You can turn the steering a lot and have the car not rotate like you want or you can steer just a little bit and send the car into a spin. As beginners, we struggle to grasp the concept of weight transfer, where the state of acceleration or deceleration heavily influence the rotation of the car.

Understanding Weight Distribution at Constant Speed

Imagine a car with 50% weight distribution between front and rear. The front and rear axles are being compressed against the track equally. This 50/50 balance is true as long as the speed is constant, whether the car is moving or just stopped. Let's assume the car is slightly understeer in this scenario.

Weight Transfer During Braking and Acceleration

If we start braking slightly, just like you would be thrown forward inside a bus if you're standing when the driver breaks, inertia makes the weight of the whole car move forward, making the front tires receive substantially more weight on them while the rear tires get unloaded.

If we start accelerating slightly, just like you would be thrown backwards inside a bus if you're standing when the driver accelerates, inertia makes the weight of the whole car move backwards, making the rear tires receive more weight on them and unloading the front tires.

How Weight Transfer Affects Steering

When we turn the steering, the front tires initiate a rotation by pointing the front of the car first and the rear tires react to that by resisting or limiting that rotation.

If the car is accelerating, then the turning effectiveness of the front tires is dramatically increased, making the car turn way more and potentially oversteering. If the car is accelerating, the unloaded fronts struggle to rotate the car as much because the rear tires are holding most of the weight of the car and their job is to resist the rotation requested by the front tires.

Common Causes of Crashes and Spins

One of the most common causes of crashes and spins in beginners is unintentionally shifting weight to the front tires and inducing oversteer by breaking or lifting while turning, especially when overshooting a corner by carrying a little bit too much speed on entry.

Key Principles of Weight Transfer

The key thing to learn here is:

• The acceleration will bring extra rotation to the car whether you want it or not

• If you start breaking while turning, you will amplify the rotation of the car whether you want it or not

• If you start accelerating a little bit while turning, you will lift the front tires and have less rotation whether you want it or not

Trail Braking and Weight Transfer

That is why when we trail break into a corner, we need extremely relaxed hands to be able to handle the oversteer tendency, making micro-correction to any excessive rotation that happens. Most of the exercises in this course are heavily related to these dynamics.

Effects at Different Input Levels

These effects are more pronounced and obvious at smaller inputs because too much breaking or too much throttle can cause opposite effects due to locking under breaking or due to wheel spend under acceleration.

Adjusting for Different Cars

The middle point between when the car starts oversteering or understeering depends on the car setup and the very nature of the car, so we always have to adjust slightly to compensate for that and get the effects that we want.

That means that depending on the car, you might need a little bit more weight on the front to compensate its laziness or its unwillingness to turn and in other cars you're going to have to shift more weight to the rear, break less and stay on the throttle a little bit earlier to compensate for the fact that that car wants to rotate too much. We will practice all this in Module 3.