Introduction
In the previous article, What Is the Friction Circle? Understanding Braking, Cornering, and Acceleration on Track, we looked at braking, cornering, and acceleration as different ways of using the same limited tire capacity.
On a straight, most of that capacity is used for braking.
During turn-in, braking force is reduced while lateral force for cornering increases.
At corner exit, lateral-force demand decreases while the driven tires use more of their capacity for acceleration.
In terms of actual driving inputs, one principle becomes especially important:
Reduce one input while progressively increasing the next.
During turn-in, reduce brake pressure while increasing steering angle.
At corner exit, unwind the steering while increasing throttle.
This article follows the process from the end of the straight to corner exit and looks at how braking, steering, and throttle overlap over time.
1. Maximum Braking | Build the Required Braking Force
At the end of a straight, the first task is to generate the required deceleration.
As brake pressure increases, the tires generate longitudinal force and the car slows down.
At the same time, load transfers toward the front of the car. Vertical load on the front tires increases, while vertical load on the rear tires decreases.
The amount of force each tire can generate depends on factors such as vertical load, speed, road conditions, and tire condition.
The key during maximum braking is therefore to:
build braking force in line with the tire capacity available at that moment.
The driver increases brake pressure until the tires are being used effectively for deceleration, then prepares to release the brakes as turn-in approaches.
Practical points
- Build brake pressure smoothly
- Use the car’s deceleration and balance as feedback
- As turn-in approaches, begin transitioning toward brake release
2. Turn-In | Reduce Brake Pressure as Steering Angle Increases
Near maximum braking, a large part of the available tire capacity is being used for deceleration.
To begin cornering, the tires need to generate more lateral force.
During turn-in:
brake pressure is reduced as steering angle increases.
Reducing brake pressure decreases the amount of tire capacity being used for longitudinal braking force.
That allows more capacity to be used for lateral cornering force.
At the same time, carrying some brake pressure into the beginning of the corner maintains some forward load transfer and changes the balance of available capacity between the front and rear tires.
The car therefore moves from braking toward cornering by overlapping two inputs:
less brake, more steering.
In general, brake pressure decreases as steering angle increases.
The exact point at which brake release begins, and how much brake pressure is carried into the corner, depends on the corner, speed, and vehicle characteristics.
Viewed through the friction circle, this is the basic idea behind trail braking.
Practical points
- Release brake pressure progressively as turn-in begins
- Reduce brake pressure as steering angle increases
- Treat brake release and steering input as one continuous transition
3. Mid-Corner | Avoid Sudden Changes in Tire Demand
During the middle of a corner, a large part of tire capacity is being used to generate lateral force.
At this stage, abrupt changes in braking, throttle, or steering can quickly change both the forces demanded from the tires and the load distribution across the car.
Examples include:
- suddenly adding brake pressure
- abruptly lifting off the throttle
- rapidly increasing steering angle
Each of these can quickly change the job being asked of all four tires.
If the front tires approach their limit first, the car tends toward understeer.
If the rear tires approach their limit first, the car tends toward oversteer.
The useful question during cornering is:
Which tire am I asking to generate more force, in which direction, and by how much?
Practical points
- Pay attention not only to how much input you use, but how quickly you change it
- Make changes in brake, throttle, and steering progressively
- As the car begins to point toward the exit, prepare for the transition to acceleration
4. Corner Exit | Unwind the Steering as Throttle Increases
At corner exit, the process shifts from cornering toward acceleration.
As the car becomes aligned with the exit and the steering wheel begins to unwind, the required lateral force decreases.
The driven tires can then use more of their available capacity for longitudinal acceleration.
The basic relationship is:
less steering, more throttle.
While a driven tire is still generating a large amount of lateral force, its remaining capacity for acceleration is limited.
As steering angle decreases and lateral-force demand falls, more drive force can be used.
This creates an important distinction between:
beginning to apply throttle early
and
being able to use a large throttle opening early.
A small amount of throttle may be introduced relatively early in some corners.
A large throttle opening becomes possible as the car is better aligned with the exit and the lateral demand on the driven tires falls.
Which tires generate the drive force depends on the drivetrain layout.
In a front-wheel-drive car, the front tires handle both cornering and drive force.
In a rear-wheel-drive car, the front tires mainly handle cornering, while the rear tires generate both lateral force and drive force.
In an all-wheel-drive car, drive force can be distributed between the front and rear tires.
Practical points
- Begin using throttle as the car starts to align with the exit
- Increase throttle as steering angle is reduced
- Use larger throttle openings as lateral tire demand decreases
5. Why Sudden Inputs Tend to Cost Lap Time
When the tires are already operating near their limit, very little spare capacity remains.
If an abrupt input pushes the front or rear tires beyond their available grip, the car may move into understeer or oversteer.
The driver then has to correct the situation by doing things such as:
- reducing throttle
- correcting steering
- delaying acceleration
The time and distance spent making those corrections cannot be used to follow the intended line or accelerate out of the corner.
It is faster to keep the tires within their usable capacity from the start than to exceed that capacity and spend time correcting the car afterward.
Conclusion | Fast Cornering Is About Overlapping Inputs
From the end of the straight to corner exit, the basic sequence is:
Heavy braking
→ Reduce brake pressure while increasing steering angle
→ Transition toward primarily cornering
→ Unwind steering while increasing throttle
→ Build toward stronger acceleration
Braking, steering, and throttle overlap in time as one input hands over to the next.
What matters is not only how much input the driver uses, but also:
how quickly brake pressure is released,
how quickly steering angle is increased,
how quickly steering is unwound,
and how quickly throttle is added.
By matching those rates of change to the car’s balance and the tires’ available capacity, the driver can move smoothly from braking to cornering and from cornering to acceleration.
The friction circle provides a useful map for understanding that process.
Fast cornering is less about finding one moment of maximum grip, and more about carrying tire capacity smoothly from braking into cornering, and from cornering into acceleration.
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