It’s far more complex and difficult than I'd imagined. Stating the obvious, first you have to figure out what you are supposed to do, that how you're supposed to do it, and finally you have to practice it enough such that you can do it really smoothly, really fast, and (occasionally) while you’re scared shitless. Fortunately, it's really a lot of fun.

Driving fast is mostly turn exit speed. Only in a Hollywood car chase does the good guy catch the bad guy by using the clever "shift gears and floor the throttle" trick. In real life, the other guy knows that trick too. If both you and I have the same horsepower and you come out of a turn with 1mph more than I, nothing I can do will prevent you from leaving me as we accelerate down the stretch that follows.

Maximizing turn exit speed requires being at the limit of your tire traction. Not just visiting the limit, but living there, turn after turn. There is an oft quoted remark that states, "your tires can only do a 100% of something". If you are using 90% of a tire's traction for braking and you suddenly turn the steering wheel demanding 20% traction for turning, the car is not going to turn. You've got four tires. The traction that each can give you, instant by instant, varies because the amount of weight on that corner varies. As you gain skills, you will intuitively sense the amount of traction available at each corner, hearybeat to heartbeat, and the use your driver inputs to use 100% of what's available. If you use only 90% you'll be slow. If you use 110%, you'll be in the grass.

Planning mode, not reaction mode. Our daily commute is characterized by "reacting" to changing conditions. Approaching a busy intersection or merging on to a freeway doesn't normally require "a plan." In contrast, on the track, the execution of every turn is a carefully planned event. As you head towards a turn you start forming your plan for braking. You choose where to start braking based on the geometry of the turn. So just before or early in the braking your eyes need to be on turn exit so that your brain will have the information necessary to calibrate how much speed you can take into the turn and how much steering input will be needed. You're not thinking about what you are doing, present tense--standing the car on it's nose braking at 125mph towards a turn-in point at track edge. You are thinking about what you are about to do, future tense--getting off the brakes and turning. The objective is for your eyes, and therefore your brain, to always be focused on forming the "next plan" while you are executing the current plan.

What you are aiming for is to keep your eyes way up and looking as far down the track as there is useful information. This is so important that you might have to imagine what you can't actually see. If the geometry of the turn is such that you can't see the turn exit, don't focus on the visible first half of the turn. Instead, resolutely imagine the geometry of the turn exit that you can't actually see. Only by focusing on the turn exit can you calibrate brake, steering, and throttle to maximize your exit speed. Otherwise your brain won't have enough information to drive fast, and you'll find yourself making corrections as more of the turn become visible.

Forebrain vs. reptile brain.  Your forebrain plans. Your reptile brain reacts and executes. Your goal is to always have a plan and then, at the appointed moment, unhurriedly execute your plan. As long as you are executing your plan, you won't feel rushed--You won't feel overwhelmed by all the sensory input. In fact, if you do feel overwhelmed on the track, it's probably because you are no longer keeping your eyes well ahead of your bumper and focusing on turn exit while still in the turn's braking zone. When people start feeling overwhelmed, they often make the mistake of letting their awareness contract.

Control your brain by controlling your eyes. You will think about what you are looking at. Force yourself to look at turn exit well before you enter a turn. This will give your brain the information necessary to calibrate entry speed and steering input. While approaching or in the braking zone, your eyes won't want to move to turn exit. Force yourself. Get your eyes back up, 5-10secs ahead of the car, and get back into planning mode.

Novices get overwhelmed and exhausted easily. It takes time to train up the reptile brain so it can handle "immediate action" tasks without the forebrain, wearing itself out, having to think through and guide every little step. To a novice 20min at the limits of their skills will be exhausting. The veteran, with his reptile brain handling most tasks on autopilot, can go for hours and hours and not be mentally as worn.

Braking. "Threshold braking" is braking at the very limit. That is to say, all the braking you can do without skidding. Surprisingly, at least to me, when you are braking at threshold your tires are turning ~10% slower then you are moving. So a fair amount of skidding is actually already occurring. ABS and Traction Control systems vary significantly in sophistication so different cars will react differently when approaching threshold conditions.

A novice starts out by carefully doing all his braking in a straight line. They are generally taught a mantra of slowly saying "Brake and then turn" that helps them create a clear separation in time between doing one thing, and then doing the other. That way you can brake at 100%, get off the brake, execute the turn-in, and have 100% available tire adhesion to resist the lateral forces of the turn.

Turning.  As mentioned, the key to being fast is turn-exit speed. Useful, but not as important, is getting through turns quickly. Those two ideas are more different than they might appear. Turn exit speed means an advantage down the whole straight that follows. Being faster in the first half of a turn is only a fleeting gain. 

There are lots of ways to take a corner. The "line" that you choose is dependent on what’s before and after the corner, and anything that might impact traction in the corner like camber and/or elevation changes, and corner’s road surface. But to make things easy, we’ll stick with an isolated theoretical corner.

The diagram to the left is intended to show why the theoretical standard racing line is more efficient than an inside line or an outside line. Note the 3 different "lines" thru the turn, each with a different radius and theoretical max speed.

Inside line. Car enters and exits the turn at the inside. Turn radius 103' and speed a relatively slow 39mph.

"School line". Car enters and exits turn from the outside. But car used the whole track width to open up the radius of the turn. Turn radius 195', speed 54mph. The point where this car hits the inside of the corner is called the Apex. This "using the entire track width" is the classic line that novices start with.

Outside line. Car enters and exits turn from the outside. Car does not use the width of the track to open up the radius of the turn. Turn radius 130', speed 44.1mph.

Not that also the School line, the line that uses all the track width, is also the longest way around the turn, the greater exit speed hugely dominates the result.

 The "apex" of a turn is a critical issue. Note the "rumble strips" on the inside edge of the turn, those are brightly painted bumps designed to punish those that would try to gain a little track width that god hadn't intended.  The apex of the turn at left is depicted by a small circle in the center of the rumble strip. The idea is that the apex is the halfway point of the car's change of direction. 

Like everything else, it’s far more complicated then this simplification describes. The apex that a driver chooses doesn't have to be at the geometrical halfway point of the pavement's inside edge.  A driver will often choose to "late apex".  This means that he deliberately "turns in" late. As a result of turning in late, the driver will initially turn a bit sharp, also. The result of getting a bit more turning done early will be that, by the turn's half way point, the "late apex" type can start straightening out his steering wheel--the whole purpose of the late apex line. Less steering input at the turn's halfway mark means more traction available for throttle. Getting on the throttle early is good for turn exit speed.

The interaction of gas pedal and your car's willingness to turn is all pretty easy to control after a while. Noting that this is a bit of a simplification--if you're near 100% of your traction budget and simultaneously accelerating and turning, briefly asking for less acceleration or less turning gives you more of the other. The softer your tires are the harder this is to control. Street tires are generally forSoft race slicks, for example, tend to have lots of grip, right up until they don't have any grip. So they have a narrow envelope of controlled slip.

Turns that are tied together. If there are a couple turns in rapid succession and a straightaway follows, the second turn is probably the important one because it will set the speed for the straightaway. In that case try a line that compromises the first turn in order to set up for a really good run out of the second. Usually this means exiting the first turn on the inside of the track in order to have the car ideally placed to use all the track width for the second turn.

Driving fast is as much art as science. There is no perfect line for your car in a turn. For a specific turn, listen to different ideas, watch them in practice, study data if so equipped, then try to make those ideas work. Some of the ideas will work for you, some won't. Two classical painters might both do amazing work, but they both do it their own way. I had a hard time with this when I was starting out. As an engineer, I pressed my every instructor for the "optimum" line through a turn and was frustrated by the ambiguous answers. I have a vivid memory of sliding through a turn I knew very well, at the absolute fastest speed that was possible in that turn for my class of car. Which is when one of the best drivers in the nation passed me on the inside, something that should not have been possible. His greater skills found traction that I'd have sworn didn't exist.

The car’s balance. A tire’s ability to hang on to the road is a function of how much weight is on that tire. Obviously when you brake, the weight of the car shifts forward. That means under braking your front tires gain traction and your rear tires, because they become light, lose traction. When you accelerate the opposite occurs. Weight is added to the rear tires so they gain traction, and weight is removed from the front tires so they lose traction. To make things more interesting, there is an opposite traction variable at work. Braking gave your front tires more traction, but your front tires also do most of the work of braking. So the front tire traction went up, but the demands on that traction also went up. When you accelerate the weight on your rear tires makes their traction go up, but the demands on that traction also go up.

When you turn left, the right-side tires are weighted and the left side is light. So your right-side tires get more traction, but it's also those right-side tires that are doing most of the work of turning. So once again you're adding traction and also taking it.

Even a novice on their first day will be turning and accelerating simultaneously. As one improves, they'll work on braking and turning simultaneously. As a result, the weight at each corner of the car, and therefore traction at each corner varies rapidly, as does the demands for traction from that corner. With practice one gets reasonably adept at dancing driver inputs through a turn in order to optimize turn exit speed. It can be quite exciting.

The discussion of being within or exceeding available traction creates an image of tires gripping or slipping. The reality is more complicated because tires have the most grip when they are slipping a bit. Depending on the model, tires are most efficient in a turn at a slip angle of 4-7 deg. So if you compared a car's line though a turn to where it's tires were pointing, at optimum traction front tires would be pointing 4-7deg too sharply.

Quick definition of critical terms: Understeer and Oversteer. Understeer is when your front end is washing out so the car does not want to turn as much as you want it to. If your car understeers, you go straight off of the turn. Oversteer is when your rear end starts losing traction and the car wants to come around on you. If your car oversteers, you go off the turn backwards.

To reduce understeer, help the front tires grip. This could mean less steering input so you're not asking so much of the front tires. If on throttle, reduce it so weight will go forward and add traction to the front tires. If braking, reduce it because it doesn't take much braking to consume a lot of the available front traction.

To reduce oversteer, help the rear tires grip. Steer into the oversteer a bit so that the car will drift sideways instead of rotate. If on the throttle, back off just a little so the rear tires aren't working so hard. Don't back off all the way--a bit of throttle is keeping the rear weighted. Front wheel drive cars are pretty docile in over-steer. Give it a bit more gas and the front tires will probably pull you out of it.

Managing oversteer and understeer is a reptile brain task, and it takes a while to train up the reptile brain to handle it. The forebrain doesn't work fast enough to handle this sort of thing.

When you are going thru a turn at the limit of tire adhesion, you have to balance understeer and oversteer, second by second, with throttle and steering inputs. If you heard the phrase "steering with your accelerator", that’s what is happening. With your gas pedal you can change the amount of weight on the front tires vs. the rear tires, and the amount of traction your demanding from the rear tires, second by second. The changing inputs change how much slip you'll get, both front and rear, and therefore you can exercise some control over how the car is rotating in the turn. 

It’s important to note that understeer and oversteer can be significantly altered by tire size and suspension set up. Modern cars are all set up to understeer. This is to help shield car manufacturers from law suits. Apparently juries are more apt to blame the driver if their front end washes out (understeer) and they go off of the road, but more apt to blame the manufacturer if the driver spins off (oversteer) of the road.  You can "dial-out" some understeer by increasing the negative camber of the front wheels.  Negative camber looks like your wheels are leaning a bit inboard.

Heel-and-Toe. This is "blipping" the gas pedal while, you are still on the brake, to match rpms while downshifting. There's two common techniques. With the ball of the foot on the brake pedal, some drivers rotate their foot and blip the gas pedal with their heel. Others use the outboard portion of their foot, under the small toe, to blip the gas. Often drivers will modify their pedals to get them closer together. 

Anyone that has driven a manual understands the occasional need to downshift. Most folks understand that you should make an effort to match RPMs when you downshift and release the clutch, you'll get a smoother downshift, which is easier on your clutch. The issue of matching rpms in a downshift is more significant on the track because RPMs are high. You’re generally above 4k RPMs, because that’s where the power is. So instead of downshifting and trying to use the throttle to match rpms at 2-3k rpm, you could easily be downshifting and trying to match rpms at 5k. At the same time you're braking really hard, driving the car, and planning your line through the turn. Heel-and-toe is entirely a reptile brain activity.

If you fail to blip RPMs up in downshift your clutch will be forced to mate a transmission input that is spinning fast with an engine output that is turning slow. The result will be braking action at the drive-wheels. If you're already using all the available traction for turning or braking, the braking action of the failed RPM match will cause the drive-wheels to slip. Once again you asked for more than 100% of the available traction. Being in the middle of a high speed anything and suddenly your rear wheels slip is not ideal.

It's hard to practice heel-and-toe during your daily commute because on the streets one doesn't press their brake pedal very hard. With the brake pedal only barely depressed into the foot-well, the foot is the wrong location to rotate to the gas pedal and practice heel-and-toe. The only place that I found to practice was the garage. Not quite the same, but very forgiving of mistakes.

Putting it all together.
You exit a turn at 105mph and head down a 1/2mile long straightaway towards Turn 1. When the tach hit's the redline you shift to 5th. You glance ahead at the next flag station to see if there's any flags showing, particularly a waving yellow flag.

The Turn 1 Brake Zone Markers are approaching. You're doing about 125mph and you're are on the far outboard side of the track. Your brake point is Marker 2. Any later than that, and you'll end up in the trees. 

You get off the gas and push the brake pedal to 50%, then 100%. While violently standing the car on it's nose, your eyes shift to the turn's exit. Altho the turn's apex is plainly visible in the foreground, it's the turn's exit that you really have to concentrate on. This gives your brain the information needed to calibrate entry speed and plot your turn-in point.

This idea of "what do you look at in the braking zone" is so critical that it's worth going over a second time. You are braking so hard that you're barely in control. You're heading towards a turn-in point at high speed with barely enough distance to allow for sufficient braking. Because the turn in point is at track-edge, if you screw it up by more than a couple inches, you'll be off the track. So the calibration of speed and the timing of turning are significant emotional events. Yet, you aren't looking at the turn-in point. Instead, you must look at the turn exit. Everything about the turn-in, timing, speed, and the initial amount of steering input, is based on the geometry of the latter half of the turn. If you do it right, you'll be on the gas early and your sliding path will use every inch of track width. In fact, there will be a few heartbeats, while sliding thru the turn, that you won't think that you'll be able to stay on full throttle and still stay on the track. So you'll dance the driver inputs and somehow find a way to squeeze out just a bit more traction and somehow make it work. If you fail to concentrate on the latter half of the turn, prior to turn-in, nothing will go as well as it could have. Your turn-in speed will be wrong, your line through the turn won't exploit all the track width and will therefore be too tight, and your initial steering input will be wrong and therefore require adjustments on the fly. So you'll either be slow, or off the track.

If you can't yet see turn-exit, you tenaciously imagine it's location.

Back to the braking zone. As you pass about 90mph and while still pressing the brake pedal hard, you hit the clutch, and make the awkward shift from 5^th to 3^rd (Some folks execute 2 shifts, 5th to 4th, and then to 3rd, but it's not my preference). Then, while keeping the ball of the foot firmly on the brake, you sneak the outboard side of your braking foot over to the gas to give it a "blip" as you release the clutch. If it goes well, you won’t surprise the rear tires which could result in you suddenly being backwards.

With your eyes looking at the turn exit far away, and your foot reducing brake pressure, you start applying steering input just prior to completely coming off the brake. In a racing environment, you have to turn-in at a speed that seems not quite survivable becuase if you're not scared, you're slow.  The car is in now in a 4 wheel drift. You're going so damned fast that you don't dare add throttle, yet to keep the drift going exactly right, you have to dance with small steering input adjustments and yes, small throttle adjustments too. You sense that you soon will have some spare traction, so you press on throttle. Being on the throttle early is critical for turn-exit speed, so it's best to go to throttle before it really seems survivable. Somehow, find a little more traction.

You will drift past the apex and start sliding towards the track edge at turn-exit. Unless you're absolutely sure that you're going to die, stay at full throttle. Dance the driver inputs and changing track surface to find a way to keep the car from sliding off at turn-exit. If you just did much better than usual, you might have an additional 0.5mph to carry down the straight that follows.

Trail-braking.
As you get better, you’ll hear about "trail-braking" which is creating a bit of overlap between coming off of the brakes and the initial steering input at turn-in. It's an issue that gets confused a lot. Most people don't have any background in physics, and it's easy to fool one's self re. what the car is doing and why it's doing it. As a result, trail-braking discussions are usually a bunch of non-rigorous silliness where people start with different definitions of "trail-braking" and then break various laws of physics explaining it. Once you get pretty skilled, certainly experiment a bit with some overlap between brakes and steering at the turn-in point, and see if you can make something useful happen. Do this on slow turns.

Personally, I was not able to make trail-braking work. It just made me slow.

Everything I just wrote is rift with simplifications. There’s a number of exceptions and alternatives to every point I attempted to make. Like all human endeavors, it's harder then it looks.

There are all sorts of books on performance driving. A particularly good one is based on the Skip Barber Driving School’s. It’s called Going Faster. If you get the bug, get more then one book. Memorize the books and then take the apparent contradictions and ambiguities to instructors or licensed racers and get their input. Then get on the track and try to make sense of it all.

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