Handling Characteristics & Cornering

When the front tires have less traction than the rears do, the car tends to “push” or plow relatively straight ahead, rather than turning as much as you’d like. That’s understeer. The car has not steered as much as you’d like, so it is understeering. 

Understeer is a function of car’s inherent dynamics, a lack of weight transfer to the front wheels, and/or too much entry speed.

Therefore, the front tires don’t have enough traction to change the direction of the car as much as you’d like.

When the rear tires have less traction than the front tires do, the rear of the car will slide more, causing the car to turn — or steer — more than you wanted. Therefore, it has oversteered.

Oversteer can be caused by too much weight transfer to the front, too much (or too sudden) application of throttle, or by the car’s inherent dynamics.

If you don’t manage the weight transfer properly, the car will oversteer. Or the combination of suspension setup, aerodynamic downforce balance, and tires can also lead to your car oversteering. It’s important to learn how to identify each one, so you can “fix” the problem (and not something that you think is the problem).

A tire’s slip angle can be viewed as the difference between the direction the wheel is pointing and the direction the car is heading.

When driving at the limit, there is a certain amount of slip (actually, twist between the tire and the wheel).

Surprisingly, tires generate more traction when there is some amount of slip (see Slip Angle vs. Traction graph).

SLIP ANGLE IS THE DIFFERENCE BETWEEN WHEEL DIRECTION & DIRECTION THE CAR IS HEADING

The first graph compares traction/grip to a tire’s slip angle.
As the slip angle increases the tire actually gains traction until it plateaus and then falls off, resulting in sliding and potential loss of control.

The graph below shows 4 different drivers: Driver A spends most of the time driving at less than the limit. Driver D is over-driving the car, spending too much time with the tires beyond their limit (note that this doesn’t necessarily mean spinning or crashing — it can just be too much sliding through corners).

Drivers B & C would have roughly the same speed around a track because they spend the same amount of time in the peak traction zone, but Driver B would be faster over time. Why? They’re putting less wear and tear on the tires.

There’s a lot going on in these illustrations and  all are related. So, take time to fully understand what’s going on here.

The track illustration shows a car going through a corner and what is happening with braking, cornering, and accelerating through the turn.

The accompanying Traction Circle shows the amount of traction the tires have and the direction of the force during the turn. Think about how your body is forced forward when you break hard, or how you are tilted to the left when you turn to the right. The same forces are at play on your tires.

Keeping your tires within the circle (maintaining traction) is what driving “the limit” is all about.

Note the relationship, or interplay, between the steering wheel and the throttle and brake pedals. You’re constantly trading off braking for cornering, cornering for braking, acceleration for cornering, and cornering for acceleration.

You can only ever use 100% of your tires’ traction, no more. If you want to use 5% for accelerating out of a corner, you can only use 95% still for cornering. In other words, you’re going to have to unwind (straighten) the steering wheel by at least 5% to use that for accelerating.

HOW YOU MANAGE YOUR TIRES BY BLENDING BRAKING, CORNERING AND ACCELERATING IS AT THE CORE OF HIGH-PERFORMANCE DRIVING.

Imagine having a string attached to the bottom of the steering wheel, and to the top of the gas pedal when it’s fully depressed to the floor — it’s tight. As you turn the steering wheel, the string will pull the top of the gas pedal upward, right? 

Once it’s pulled all the way up — zero throttle — the steering wheel is fully turned to use up all the tires’ traction. Then, as you come out of a corner and squeeze on the gas pedal, it’s going to straighten the steering wheel.

The interplay of the throttle and steering wheel are critical when exiting a corner. Step on the throttle too soon (when you still have too much steering angle in), and you’re asking for more than 100% from the tires. Expect to experience a skid, slide, or spin.

Every corner can be described by three reference points: Turn-in, Apex, and Exit (or “Track-out”). The simplest instruction is to keep two goals in mind: Straighten the corner out as much as possible, and drive it in such a way that it allows you to begin accelerating early (the speed on the straight after the corner is usually more important than the speed through the turn).

It also shows how you want to use all the track, entering from the outside edge of the track (at the Turn-in point), to the inside at the Apex, and then back to the outside edge at the Exit.

This also illustrates what is referred to as a “late apex line,” as the apex is beyond the middle of the corner.

Using this line allows you to begin accelerating earlier, and therefore end up with a faster straightaway speed (possibly even for accelerating onto a freeway).

As you can see from this illustration, if you turn in early, you’ll clip an early apex, and ultimately “run out of track” at the exit.

Your Turn-in point is critical, so having a good reference point for it is key.

ACCELERATE EARLY TO END UP WITH A FASTER STRAIGHTAWAY.
AVOID EARLY TURN-IN SO YOU DON’T RUN OUT OF TRACK.

THE BENEFITS OF A LATE APEX (IDEAL LINE)

• It allows later braking, since you’re going to turn in later;

• You spend less overall time in the corner, and that means more time spent accelerating;

• It means you can start accelerating earlier;

• What’s not really indicated here, but is an important benefit, is that it allows you to see, or “peek” around the corner better.

The gray line demonstrates the geometrically largest radius – the fastest way to drive through the corner in isolation – but as you can see, you spend practically all of the 300 feet cornering. Until you begin unwinding/straightening the steering wheel, you can’t start to accelerate. 

By turning in and apexing later, it allows you to accelerate earlier, meaning you’ll be faster on the following straightaway. As the speed trace diagram shows, you will be a little slower at the beginning of the corner, but you’ll more than make up for it later in the corner and down the straightaway. This is why the late apex line is referred to as the “Ideal line.”

Speed in vs. Speed out

If you have a corner with very little straightaway after it, your focus should be on carrying as much speed into it, and not worry so much about exit speed. 

Having said that, there are very few corners like this, so don’t get carried away with this!

Snaking around

Here’s how you would approach and drive a series of corners like Esses. The lesson here is that you’ll have to compromise at least one corner to maximize your exit out of the final corner. In other words, your priority should be how quickly you get out of the last corner.

Don’t Get Crabby

Here, we’re illustrating how NOT to do it. 

This driver is “crabbing” into the corner, pulling the car away from the edge of the track before the Turn-in point, reducing the radius of the corner – meaning the car will not be able to carry as much speed through the corner.

In the first illustration, the driver has turned in too early (before the Ideal Turn-in point), resulting in an early Apex. The driver would have to delay beginning to accelerate to avoid driving off the track.

In the second illustration, the driver has turned in too late, resulting in a super-late Apex. While safer than the previous mistake, the amount the driver would have to slow down for the very tight radius early in the corner would be impossible to make up for – the driver would be slow down the straightaway. 

The key indicator here is the space between the car and the edge of the track at the Exit. Next lap, the driver should aim to turn in at the right point and clip the ideal Apex.

In the third illustration, the driver turned in at the right place – at the Turn-in point – but they turned too abruptly, too sharp, resulting in an early Apex. Ultimately, it ends up very similar to the first illustration – delayed acceleration to avoid running out of track at the Exit.

Which is best? That depends on: 

• Track conditions 

• How the car handles 

• Car’s acceleration capabilities 

If it were raining, the Exaggerated Late Apex might be better, providing a straighter line for acceleration. In contrast, if the car had little power, the momentum you could carry through the corner with the Standard line might be better. 

EXPERIMENT WITH THE LINES THAT YOU DRIVE TO FIND THE IDEAL COMPROMISE.

Use All the Track

Not using all the track width is a big no-no.

Even just being 1 foot away from the edge of the track as you enter a corner can have a big negative impact — reducing the turn radius more than you might imagine. 

Subtle Differences

The differences in the line you drive can be subtle, as this illustration demonstrates. The corner on the left is a slightly tighter radius than the one on the right, so it requires a later Turn-in and Apex line. 

However, both of these illustrations are showing early Turn-ins – both would benefit from a later Turn-in and Apex to maximize straightaway speed.

YOU PAID TO USE THE TRACK — USE IT ALL!