by Ross Bentley
In general, the shorter and tighter the corner and the longer the following straightaways on either side, the more the line should be altered from the geometric line. In other words, a later turn-in and apex. Similarly, the greater the acceleration capabilities of the car, the later the turn-in and apex.
Many drivers seem to fall into the habit of driving all corners the same. They fail to adjust their driving appropriately for the different conditions—corners or cars—even though they may drive the car at its traction limit. This may explain why some drivers can be very fast in one type of car or at one track and yet struggle when they get into another car or drive another track. A true champion driver can quickly alter his or her line to suit the track and car, and of course, always drive the limit.
CONTROL PHASES
Breaking the cornering technique down further, there are six activities or phases you go through with your feet on the throttle or brakes in a corner (Illustration 8-3): braking, trail braking, transition, balanced throttle, progressive throttle, and maximum acceleration. The length and timing of each of these phases vary, depending on the car you’re driving and the type and shape of corner. When you add the turn-in, apex, and exit reference points to the equation, you have the formula for a successfully completed corner.
Taking a closer look at the braking phase, think of the brakes as a waste of time. Brakes are merely for adjusting speed, not for gaining much. So if you are looking to improve more than one-tenth of a second on an average road racing circuit, don’t just look at the brakes. Don’t think that by braking later you’ll gain a great advantage. You’re going to make up more time with the throttle on, not off.
SPEED SECRET
The less time spent braking, the faster you will be.
Racers are always talking about brake reference points. They’re always comparing and bragging about how late they begin braking for a corner. But the important reference point is not where you start braking, but actually where you end maximum braking. Only use brake reference points as back-up.
Instead, when you begin braking for a corner, focus on the turn-in point to visualize and judge how much braking is necessary to slow the car to the proper speed for entering the turn. Your speed at the start-of-braking may be different due to how well you entered the straight, so that reference point will constantly need slight adjustment. You need to analyze and sense the speed and adapt your braking zone to be at the correct speed at the turn-in reference point so you enter the corner at the ideal speed.
I always wondered why I could never remember where I started braking for a corner, where my braking point was. This was until I realized that I concentrated more on where I needed to have my maximum braking completed, the turn-in point, and the speed I wanted to slow to, instead of the start-of-braking point. Every driver has his or her weak and strong points. One of my strong points has always been in the braking area, which I attribute to my concentration on this “end-of-braking” point.
The most controversial control phase is definitely trail braking. Some “experts” say you should never trail brake. Complete all your braking and be back on the gas by the time you reach the turn-in point. Others say you should trail brake at every corner on every track. Of course, the truth lies somewhere in between. In some corners in some cars, you need to trail brake a lot, and in others use little to no trail braking. It varies depending on the corner and the car you’re driving. Your job is to determine what works best and the ability to vary how much you trail brake.
How do you determine how much to trail brake in each corner (and car)? Begin by asking yourself, “Does the car turn in to the corner well?” If not, try trail braking a little more, gradually easing (trailing) your foot off the brakes as you turn in. Or, does the car feel unstable or unbalanced going through the turn? If so, try coming off the brakes and getting back on the throttle just as you turn in. In this case, there may not be a trail-braking phase at all.
ILLUSTRATION 8-2 The control phases of a corner.
The transition from braking to acceleration is one area of your technique that may adversely affect the balance of the car most. You should be able release the brakes and begin application of the throttle without feeling the transition whatsoever and as quickly as possible. It should be immediate, as fast as you can possibly move your foot from the brake pedal to the throttle.
ILLUSTRATION 8-3 The effective length of any corner is from turn-in to the point where you get back to full throttle. This illustration demonstrates how much less time you spend cornering by using a late apex. Note how much more straightaway there is prior to the turn-in point for braking, or how much longer the straightaway is for maximum speed, with the later turn in.
Practice this when driving your street car. You should never be able to feel the point where you ease off the brake pedal and begin to squeeze on the throttle.
A correctly executed transition from braking to acceleration is paramount. It must be done with perfect smoothness. That’s one big reason why one driver can make a car turn into the corner at a slightly higher speed than another driver. Just because you cannot make your car turn into the corner at a specific speed, does not mean Michael Schumacher or Dario Franchitti couldn’t. Maybe you are not using the correct technique, not being smooth enough, turning the steering too quickly, unbalancing the car, and so on. Again, how you lift your foot off the brakes is absolutely critical. It has to be eased off the pedal—quickly—so as not to upset the balance of the car. Then, you have to transition over to the throttle so smoothly that you never actually feel the exact point where you have come off the brakes and where you start to apply acceleration.
Remember the traction circle. The relationship between steering position and throttle position is interactive. Steering input must be reduced (“unwound”) in order to apply acceleration. Since a tire has a limited amount of traction you cannot use all of it to turn the car and expect it to accelerate at the same time. You have to trade off steering input as you begin to accelerate, otherwise you “pinch” the car into the inside of the corner on the exit, often causing the car to spin and always scrubbing off speed.
And remember, given relatively equal cars, the driver who begins accelerating earliest and hardest will be the fastest on the straightaway. I think that tells you everything you need to know about the progressive throttle and maximum acceleration phases.
I want to start the discussion on how to master the line with a reasonably obvious (if not, perhaps, something that you are consciously aware of) piece of physics: Corner speed is proportional to corner radius.
What does this really mean? Simply that the more speed you carry through a corner, the larger the radius of the turn must be. Alternatively, the tighter the radius of the corner, the slower you must drive. Simple enough, right? And, like I said, even if this is something you had not consciously thought of before, I’m sure you knew this at the intuitive or subconscious level.
Of course, I’m talking here about driving at the limit, with the tires at their very limit before breaking loose and beginning to slide the entire way through the turn.
Now, let’s take this physics discussion a step further. As you also know at the intuitive level, the tighter the radius or the faster you drive through a corner, the more you feel the g-forces and the more g-forces the car is generating. Again, I know you know what a g-force is from an intuitive point of view, but what does it really mean?
G-force is the lateral force acting on the car and you while going around a corner, with 1.0 g being equal to the force of gravity pushing laterally (sideways) on the car.
Now, let’s put these two facts (speed is proportional to corner radius, and the faster you drive or the tighter the radius of the turn, the higher the g-forces) together into one mathematical statement: S = g/R (S represents speed in miles per hour, g is lateral g-force, and R is the radius of the corner in feet). In other words, the speed you can drive through a corner is proportional to the amount of g-force generated, divide
d by the corner radius.
What does this really mean, and why do you need to know this? You probably don’t need to know the actual physics and math that goes along with this. What you do need to know, and what this really means is that the speed you drive through any particular turn is determined by the g-force your car is capable of generating—which is determined by the mechanical and aerodynamic grip the car has, along with your ability to balance the car to maximize the tires’ grip—and the radius of the corner.
In terms of your driving, then, there are two areas you can work on to maximize your speed: balancing the car (to maximize tire traction) and increasing the radius of the corner. I’ll discuss balancing the car in the sections on corner exit, entry, and midcorner. For now, let’s look at the corner radius.
Driving through a turn using the largest possible radius means following what we call the “geometric line.” This is the line that you would draw with a compass, using up every inch of the track surface, from outside edge to inside edge and back out to the outside again, on a constant radius. See Illustration 9-3.
ILLUSTRATION 9-3 The geometric line may be the fastest way to drive through one corner in isolation, but it isn’t necessarily the fastest way around the track.
If you decrease the radius of a turn by not using all the track, your maximum speed will be significantly reduced. For example, by entering a corner even one foot away from the edge of track, the radius of the turn may be reduced by as much as 1 percent. What’s 1 percent worth? As much as half a second on some road racing circuits. What’s half a second worth to you? From this I’m sure you see how critical using every inch of track surface really is.
ILLUSTRATION 9-1 Which corner do you think you can drive through the fastest? Right, the one with the largest radius. The same theory applies to the line you drive: The larger the radius or arc you follow, the faster you can drive.
ILLUSTRATION 9-2 Compare the apex point in these corners. The one on the left, with the smaller or tighter radius, uses a later apex than the larger radius turn. As a general rule, the larger the radius of the corner, the earlier the apex. Why? Because you don’t have to rely so much on accelerating hard out of the turn, since the larger radius allows you to maintain more speed through the corner.
Back to our geometric line. Although the geometric line is the fastest way to drive through each particular turn, it is not the fastest way of getting around the entire track. The reason for this has to do with the fact that there is usually something following the turns that is more important: the straightaways. If you have driven at least one race in your life, I’m sure you already know that it is far easier to pass a competitor on the straights than it is in the turns. What may not be so obvious at times is that there is more time to be gained, resulting in lower lap times, by being fast on the straightaways. In other words, it is far more important to be fast on the straights than it is to be fast in the corners.
Obviously, that doesn’t mean putt-putting around the turns at a crawl. What it does mean is driving the turns in such a way as to maximize your straightaway speed. And that means altering the line you drive from the geometric line to one that allows for earlier acceleration, one we call the “ideal line.” In most cases, that means driving a line with a later turn-in, apex, and exit. See Illustration 9-4 for an example.
The benefits of a line with a later turn-in, apex, and exit are listed here:
• You spend less overall time in the corner. When do you have the most control over your car, when you are on the straight or in the corner? And didn’t we already decide that the larger the radius the faster we could drive? Less time in the corner equals more time on the straight—or at least near straight—which is about as large a radius as you can find.
• You are able to begin accelerating earlier. The sooner you get back on the throttle and begin accelerating out of a corner, the faster you will be down the ensuing straightaway.
• You can maintain your speed on the approaching straightaway longer by braking slightly later. Because you are turning into the corner later, the straightaway approaching the turn has effectively become longer, and therefore, you can maintain your speed longer.
• And, you can actually see through the corner better. By turning into the corner a little later, it allows you to see around the turn better. On most road-racing circuits this is not a big benefit, your vision is not blocked anyway; but on street circuits particularly, with the cement walls on the inside of the turn, it can make a big difference.
Along with those benefits comes a negative, however. In this case, due to the later turn-in, your line through the early part of the turn is a tighter radius. You know what that means: lower speed. But this tradeoff is an easy decision. Yes, you have to go a little slower early in the corner, but you more than make up for it down the following straight by beginning to accelerate earlier.
Now that I’ve convinced you of the benefits of using a late apex in each corner, think about something. Does this analysis of turns and the resulting late apex line work for every corner? Not necessarily. Let me give you a general rule, a very general rule:
SPEED SECRET
The faster the corner, the closer to the geometric line you should drive; the slower the corner, the more you need to alter your line with a later apex.
Let’s take a good look at why this is the case.
CHANGE OF SPEED
Change of speed. Remember that phrase. The greater the potential for change of speed from corner entry to corner exit, the straighter the line you want your car pointed to allow for acceleration. In other words, the slower the corner, the later the apex you should use. A corner taken in first or second gear is certainly going to allow a greater change of speed than one taken in fourth or fifth gear, so you would use a later apex in the former than you would in the latter.
Based on what you now know about corner radius versus speed, you could also interpret my general rule as: The tighter the radius, the later the apex; the larger the radius, the earlier the apex, or closer to a geometric line. In simple terms, a slow hairpin will require a later apex than a fast sweeping turn.
Once again, the reason has to do with your change of speed. In a hairpin turn you will be accelerating hard out of the corner. Your change of speed will be relatively high. Your change of speed through a high-speed turn will not be so high, due to your car’s reduced ability to accelerate the faster you are traveling.
If that does not make sense, ask yourself this question, “Can my car accelerate from 100 to 110 miles per hour as quickly as it can from 50 to 60 miles per hour?” The obvious answer is no. Any car, no matter how much engine torque it has, can accelerate quicker in the lower gears than in the higher gears.
ILLUSTRATION 9-4 Driving the ideal line (the white striped line) does mean you will have to enter the corner a little slower, due to the tighter initial radius, but it allows you to begin accelerating earlier, which will result in faster speeds on the following straight. Also, you spend less overall time cornering, more time braking and accelerating.
So a general theme or objective in slower corners is to turn in and apex late, which allows the car to be driven on an increasing radius (a straighter line) when heavy acceleration is required. In faster corners, where acceleration is limited anyway, you want to use an earlier turn-in and apex, allowing you to maintain or carry more speed into the turn.
The other factor to consider here is how sharply you have to make the initial turn-in. Obviously, to turn in and apex later in the corner, you have to drive a sharper radius early in the turn. And you know what that means. Slower speed. In faster corners, the initial turn-in will be less sharp, allowing you to carry more speed.
Using a later turn-in and apex requires a significantly different speed of turning the steering wheel and a different amount and timing of trail braking than a fast corner’s turn-in technique.
ILLUSTRATION 9-5 The graph shows the speed at various distances throughout the corresponding corner. Th
e red-dotted geometric line is faster through the actual corner; the solid green ideal line is a little slower in the early part of the corner, but allows earlier acceleration, resulting in a much quicker exit speed. The extra speed at the exit will continue, and multiply, all the way down the following straightaway.
G-FORCE JUNKIES
Most people who race or are involved in any type of performance driving—myself included—are what I call “g-force junkies.” We are addicted to g-forces, that feeling of being pushed sideways or backwards in the seat, or forced up against the seatbelts. The more g-force, the better. For those who are competing on a racetrack, at least, that is usually a good thing, because as we saw earlier, the more g-force, the faster we are moving. However, that is not always the case. In fact, there are really two ways to feel more g-force:
• Increase your speed, which is one of the objectives of race driving the last time I checked!
• Reduce the radius of the corner; the tighter the line around a corner, the more g-force you will feel. But what’s wrong with that? Every time you decrease the radius of the corner, you have to reduce your speed, which certainly isn’t the objective.
So to satisfy your g-force addiction you may, without even being consciously aware of it, begin to tighten up the radius of a corner. Or, at least, not drive in such a way as to lessen the g-forces. Where this often shows up is at the exit of a corner, in not unwinding the steering wheel and releasing the car out of the turn.
The ultimate goal is to only increase g-forces by increasing your speed. In fact, one of the goals of driving the ideal line is to minimize g-forces so that you can then increase them by increasing your speed.
