First, let's be clear that the skills we will be working on today really are fundamental, not advanced racer techniques or professional stunt-car driver tricks. In Germany you would have to demonstrate proficiency in these same skills just to get a driver's license - and they require you do so in both fair and inclement weather! If you are interested in track or autocross, these skills will give you a sound foundation on which to build. If you just want to feel more confident driving your car on the street, we think you will accomplish that easily and have a great time while you're at it. You'll learn how to stop as fast as possible - even on a curve! - and how to control that unexpected skid. And you'll get lots of practice too, because knowing is not enough. To drive well in tough situations your responses have to be automatic.
So, what are we going to be doing today, and why?
Simply put, we'll be exploring traction limits in a progressive way that will develop an intuitive feel for how our cars respond, in order to make us better, safer drivers.
A key trait of a good driver is the ability to recognize the feel of approaching traction limits. It all comes down to where the rubber meets the road- the tire contact patch. As this little patch of rubber gets stressed- from braking, say- it starts complaining. At first you just hear a little scrubbing sound. The tire is starting to "work". Push it a little harder and it starts to squeal. This is the point at which the contact patch is just barely sliding a little. It's not sliding much, so you still have control. This represents maximum traction for most tires and is the reason Bob Bondurant says "a squealing tire is a happy tire." When pushed beyond this point tires start to howl. You are sliding!
The two most important things we will teach you today are how to get your car into tire-squealing mode in a controlled manner- quickly, smoothly and consistently- and just as importantly, how to respond when the tires howl and you are sliding. We'll start with the two simplest situations: straight line braking and steady-state cornering. Next, we'll throw in turning while braking, and give you some experience learning the effects and control of weight transfer while cornering. Along the way we are going to try and get you looking where you want to go.
In the second half of the day we'll really get into the art of controlling weight transfer. Using two ovals we'll work on how to maximize traction while cornering safely, and practice controlling over-steer and under-steer. Finally, we'll work on spin-control (not the Clinton kind!) and heel and toe downshifting.
Things to check before you start driving
Here are a few things to check before you even start driving. At some point during the day you may want to have an instructor go over each of these with you:
- Remove or stow anything that might shift around while driving!
Check under and behind seats. Don't forget the trunk either- a loose jack or wrench is not only noisy, it might even damage your car.
- Check your seating position carefully.
There should be a slight bend in your knee when fully depressing the clutch. You should be able to place both wrists on top of the steering wheel while keeping your shoulders in full contact with the seat back.
- Check tire pressure.
Cars and tires vary enough that you'll have to determine for yourself what your ideal tire pressures are. They should be the same from side to side of course, but the ideal front/rear differential depends on several factors. Also your tire pressures will change throughout the day, as the tires heat up. This is something you will want to check frequently and experiment with until you get a feel for what works best for you.
- Check your mirrors.
Your rear-view mirror should give you a view directly behind you. Your side-view mirrors are NOT intended to duplicate this view! There should be some overlap, but if you can see the side of your car they are probably not pointed far enough out
The first three exercises are all designed to gain handling experience at the limits of traction, in relatively simple situations. When you know which station you'll be doing first, start reading that section. The best strategy for getting the most from this program is to concentrate on reading the guide, driving, and talking to instructors and the other drivers. Then, just before you begin each run, take a moment to relax, focus on what you are about to do and visualize yourself doing it. OK, lets get going!
Threshold braking. Doesn't that just sound a heck of a lot cooler than stopping as fast as you can? You know you are in a professional situation when the instructor says "demonstrate threshold braking" instead of "hit the brakes!" So what exactly is the difference between threshold braking and slamming on the brakes? Well, for one thing, it has to do with how you control weight transfer.
Consider what happens when you are just cruising along and then suddenly slam on the brakes. The car starts out with just a light load on the front tire contact patches, when suddenly this tremendous braking force is exerted on the brakes. The tires stop turning. You are slowing down, but with no directional control because the tires are skidding. As the cars weight transfers forward, the increased pressure on the front will give you more traction, helping you stop faster. But because that weight has transferred forward there is now much less weight at the rear, so those tires also start to skid. The simple act of slamming on the brakes has transformed your Porsche into a ballistic object with all the responsiveness of a Seriously Unmaneuverable Vehicle!
Now lets try threshold braking. Squeeze on the brakes by increasing braking pressure quickly but smoothly. As braking forces build up the increased weight transfer forward is compressing the suspension, giving you progressively more traction on the front tires. Because you are squeezing smoothly these forces will build up smoothly, allowing you to control them. The tires are going to start squealing! At the first hint of tire squeal you immediately begin to modulate the brakes, easing off just the tiniest bit to avoid skidding and then squeezing again, keeping the tires working at their limit. Now you have fully loaded the front suspension, getting the most traction possible from the front tires, but because the brakes are not fully on you have little risk of locking the rear wheels. Tires squealing merrily, modulating the brakes skillfully, you maintain full control the whole time while stopping in the shortest distance possible.
Exercise #1 - Stopping in a straight line in the shortest distance possible
Accelerate to 50-60 mph. Be aware of your speed and be consistent each run. This will make learning easier and make your stopping distances more comparable. Begin braking at the marker cone and note where you end up on each run. Your goal is to be able to initiate threshold braking (tire squeal) quickly, maintain it until stopped, and do this consistently enough that your stops are no more than about 5 ft apart. When you can do this several times, talk to your instructor about trying it a bit faster- 70 mph max!
Exercise #2 - Emulate braking to enter a corner
This time, instead of using a cone to tell you where to start braking, you'll have to figure this out for yourself. The goal is to stop your car at the same point each time. Remember, you must threshold brake all the way until you are stopped! Do not ease onto the brakes and do not ease up if you see you are going to stop too soon. Stop as fast as you can each time. If you stop short, brake later next time. Talk to your instructor about trying different speeds if you are consistently within a few feet of the cone.
Exercise #3 - Combine braking and cornering
You really need to maximize traction in order to corner while braking. And what is the key to maximizing traction? Controlling weight transfer! When threshold braking you are using every bit of available traction just to stop in a straight line. All your weight is going forward. Now if you simply turn the wheel, what happens? The cars weight shifts outside, putting less weight on the inside front wheel, which promptly locks up. To maximize traction, ease up on the brakes as you begin turning in. Continue easing as you turn and more of the cars weight transfers onto the outside tires. Coming through the turn, increase braking again as soon as you feel the cars weight balance coming back.
This is a balancing act. The front end, especially the outside front tire, has lots of traction because of weight transfer. But you are asking it to do so much that despite all that weight it is pushed to its limit. The rear end is so light from weight transfer that even though you are just asking it to follow along, it is barely able to do even that much and is threatening to spin around on you. You can lock the inside front in a split second or spin the car if it gets off balance. Is this fun, or what??!
Done properly, you should hear the fronts squealing under threshold braking. The sound will change as you begin turning in and the outside front takes on more of the load. There will be a transition point where, if you are right at the limit, you will hear one or both rear tires squeal briefly. Then you are through the turn and back to front tire squeal until you stop. Other important feedback comes from your seat, informing you of the cars attitude, and your steering wheel, which will give immediate feedback if the inside front locks.
Check your tire pressure. The tires will have warmed, probably increasing pressure by a pound or two. Is the front/rear balance where you want it? Which tires heated up most, front or rear? If you haven't formed any clear impressions yet then either leave it alone or let just enough air out to get back to where you were at the beginning of the day.
The skid-pad is a cornering lab. We'll develop quite a few skills on this simple circle:
- Looking ahead to where you want to go.
- Using smooth steering and throttle inputs.
- Getting your car into its maximum cornering stance.
- Using throttle steer to change your line.
- Controlling under-steer and over-steer.
- Understanding how tire pressure affects handling.
If you've been paying attention then you've probably noticed that four of the six bullet points above pertain to controlling weight transfer! That's right. Your cars maximum cornering stance is simply the attitude of the car when its weight is distributed onto the tires so that it maximizes traction for a given cornering situation. Under-steer and over-steer result when that balance is off.
Skid-pad exercise #1: steady-state cornering.
Accelerate very gradually until the tires start working. Notice how steering is affected as the tires work harder, how the balance of the car shifts, the way the suspension gets settled if you are steady, unsettled if you are jerky. As soon as tire scrubbing is heard, but before they start to squeal, carefully ease back the throttle and do a few laps with the tires just scrubbing. Notice how if you get just a bit off line and correct too quickly you get tire squeal? Concentrate on smoothness, using very fine inputs to maintain the cars attitude. Look ahead, not from cone to cone, concentrating on maintaining a steady, precise circle. Try to do several laps of steady tire scrubbing without tire squeal and staying within a few inches of the line.
Next time out bring the car up to tire scrubbing speed a little more quickly. Do one or two nice, steady laps. Then carefully roll on the throttle, very gradually increasing speed until the tires are squealing nicely. Ease back and do a few laps, trying to keep a nice steady squeal going while staying precisely on line. Listen to your tires and engine. Feel the feedback coming from your seat and steering wheel. There is a lot going on when cornering at the limit, even on a flat, repetitive circle. Listen to your car and learn.
Finally, try pushing your tires really hard. Roll on the throttle from tire squealing speed. Something's got to give! This is where you find out if your car is balanced towards under-steer or over-steer. You may reach a point where as you try and accelerate, the car goes wide even if you try steering in tighter. That is under-steer. Or you may find your rear end sliding out on you. That is over-steer.
Check your tires. Look for the freshly-scrubbed edge from the cornering you've just done. It should be just past the shoulder of the tire, the point where the flat tread starts to wrap around onto the side-wall. Let some air out if you are barely scrubbing the shoulder. Put some air in if there is scrubbing beyond the shoulder too close to the side-wall. This is a judgment call, so talk to others, watch what they do and most of all, pay attention to how any changes you make affect your car's handling.
How tire pressure affects handling. Lets say you have been taking the advice above and got your tires pretty close to where they should be. Now you notice on the skid-pad that your car tends to under-steer. This can be fine-tuned a bit with judicious adjustments to tire pressure. To correct an under-steer tendency, either reduce rear tire pressure or increase front tire pressure. To correct an over-steer tendency, either increase rear tire pressure or decrease front tire pressure. Which is best? I knew you'd ask!
Changing tire pressure affects more than just absolute traction. It also affects responsiveness. With higher tire pressure you will notice quicker responsiveness, better feedback and road feel. So if you want to tame under-steer tendency and your car feels a bit slow up front, then put more air in the fronts. But if the steering already feels very lively and responsive, then try decreasing rear tire pressure. Make small changes, no more than 2 psi at a time.
Skid-pad exercise #2: throttle-steer.
Throttle-steer refers to the balance or tension between throttle and steering over which way your car will go. In other words, when cornering at the limit it is not only steering that determines your course. Throttle control also affects your line. Why? Weight transfer!
The goal of this exercise is to become familiar with the effects of throttle-steer. Bring your car up to speed, staying inside the center-line. When you are ready, roll on the throttle moderately, as if accelerating out of a corner. As weight transfers to the rear the front end will get light and start to slide. This is under-steer. Do not steer in the direction of the slide! Keep the wheel turned in tight, paying attention to the feel of the wheel and the cars direction of travel. Throttle is pushing the front end, forcing you into a wider line. Ease off as you start to cross the center line, letting weight transfer restore traction and steering.
Notice how the steering got light as you entered under-steer? First the steering gets a bit light as weight transfer lightens the front, giving less traction. Then as the fronts start to slide they have a lot less traction, so steering feel gets even lighter. If you are quick about it you can even "wag" the front wheels by turning quickly in (as if you want to go tighter) and back again. Doing this won't upset the car because the front's ability to control direction is so overwhelmed by throttle.
Experiment with different amounts of throttle and steering input. Get used to feeling the front end slide. Pay attention to balance. Learn to use just enough throttle, no more than is necessary to go where you want to go.
Next, over-steer. While cornering hard at the center-line, lift right off the throttle. By now you should know what to expect- the rear end is going to get light and start sliding very quickly! Immediately make a quick steering correction in the direction of the skid. It doesn't have to be a lot, just enough to get the front back in line with the rear. Then smoothly bring back just enough throttle to restore balance.
What happened? Coming off throttle lightened the rear, initiating the slide. Quickly steering in the direction of the skid stopped the rear end motion from developing into a spin. The sliding rear end scrubbed off some speed, so that once throttle was restored everything comes back into balance allowing continued cornering though at a lower speed.
Skid-pad exercise #3: advanced throttle-steer.
I lied. This isn't really advanced. Its the same stuff you just did. Only now we want you to do it a lot better. More consistent. More precise. More deliberate. Better.
Here's what to do. Start inside. Use throttle-steer to widen your line, power into the outside lane and settle into maximum cornering there. Then lift quickly and briefly, this time using throttle-steer to bring the rear end out just enough to tighten your line, scrubbing off just enough speed to allow the car to quickly settle into maximum cornering attitude in the inside lane.
Practice changing lanes from the inside to the outside and back again, repeatedly, without skidding and with only the briefest lapses in tire squeal. Listen to your tires and remember the scrubbing sound means you are approaching your traction limit, squealing means you are right on it and howling means you have passed the limit. Try to keep the tires always at least scrubbing, i.e. close to the limit, while doing these maneuvers
Ever notice how even the most minor little accident can snarl traffic for miles? After an eternity of waiting you finally get to where the big wreck should be, and it's just some little car off on the shoulder ran out of gas! Its clear off the road, impeding no one. But then just as you are ready to accelerate past, the road ahead finally almost clear, that's when you see the car ahead of you practically rear-end the car ahead of him! What are these people doing?!
Well, they're not looking ahead, that's for sure!
This little exercise is about just one thing: if you want to avoid an accident, look where you want to go! Don't look at the accident or you will be the accident! This isn't just about avoiding accidents, either. Looking ahead to where you want to go helps you be smooth and fast on the track or auto-cross and safer in everyday driving.
In this exercise you will drive a slalom, skipping cones according to a signal from the person at the far end of the slalom. That person will occasionally signal you to skip a gate. The idea is to train your eyes to look ahead while still being aware of what is around you. Your first run should be taken very slowly and smoothly. Weave through the slalom normally until you get the signal, then smoothly change your line, getting set up to slalom at the next cone. Increase your speed a bit each run but never push your comfort zone. Remember the focus is on looking ahead, not car handling skills.
If you decide to catch a little autocross action during lunch, make the most of it. Watch the balance of different cars as they go through a particular section. The fastest cars are coolest to watch, sure. But you can learn just as much by watching the slower cars, because their softer suspensions make it easier to see the cars attitude or balance.
Now we are going to start combining the skills practiced individually earlier. We'll also introduce a couple new concepts: the late-apex cornering line and heel-and-toe downshifting. Our cornering so far has been simple, but that will change as we add braking and acceleration while cornering. If time allows we may even introduce increasing and decreasing-radius turns. Everything though still emphasizes the same basic concept: controlling weight transfer in order to maximize traction.
Line refers to the physical path a car takes around a corner. Apex area is the section of a corner where a car is in its most stable maximum cornering attitude. The apex is the point on a cars line where the car is closest to the inside edge of the turn. As we shall see, the late apex line is the safest and most efficient way to take a corner. In most cases it is also the fastest way round. This is just as true for the highway, where you want to use your entire lane to maximum advantage, as it is on the racetrack where the entire track can be used.
To see why this is so, take a look at the apex diagrams. The early apex line cuts inside too soon, forcing the driver to have to suddenly turn sharper right in the middle of the turn. Braking or even just lifting off the throttle to do this will transfer weight off the rear end, the perfect recipe for a spin. (A friend of mine almost spun like this coming off 520 in the wet- while doing the speed limit!) Even avoiding a spin, this is a slow line because throttle can't be used until very late in the turn.
The geometric or middle apex line is what most people consider the way to corner- go in wide, clip the inside exactly halfway through, swing to the outside at the end. The problem here is that if you misjudge speed or traction and find yourself going too fast, you are going to run out of road. Not as bad as in the early apex, but it will still happen. The other disadvantage is that again, you can't get on the throttle until you are exiting the corner.
The late apex line enters the corner way to the outside and then gradually comes in tighter, not clipping the inside edge until about 2/3 of the way around. Because most of the turning is done in the apex area just about midway through the corner, by the time the car is headed for the apex or clipping point it is nearly pointed out of the turn. This means you can begin rolling on the throttle just before the apex. If throttle steer widens your line it's OK because the late-apex line allows room to do that.
Small Oval Exercises
The small oval will be all 2nd gear. First we'll work on driving the late-apex line. Then we will explore traction limits, learning to transition from threshold braking to cornering while setting the car up to roll on the throttle through a late-apex for a fast exit. Next we will work on generating and controlling over-steer and under-steer. Finally, we will practice four-wheel drifts and spins. And grins!
- Late-apex line. Driving at a moderate speed, follow the late-apex line. Concentrate on smoothness and precision, not speed. Gradually pick up the pace to where the tires just start working. No hard braking. No hard acceleration. No tire squeal. Not for now, that is!
- Turn-in. Now pick up the pace a little, so that some good hard braking is required. Concentrate on controlling weight transfer. Ease off the brakes as you turn-in. Get the car settled on its chassis, on the late-apex line. Roll on some throttle coming through the apex, but only about 3/4 throttle at most.
- Throttle-steer and exit speed. Pick up the pace even more, this time by gradually using more and more throttle. Controlling weight transfer is critical here! Set the car up wrong, dial in too much throttle too soon, and you are off-line and have to slow down to save it. Concentrate on setting the car up to enable rolling on the throttle earlier while staying on-line.
- Under-steer. Generate under-steer in a planned, controlled manner. Get on the throttle too hard and early. As you get "push" or under-steer the first few times, simply pay attention to how it feels. When this becomes comfortable, prove it to the instructor. Quickly "wag" the front wheels, turning the wheel back and forth during under-steer.
- Over-steer. Generate over-steer in a planned, controlled manner. Brake a bit late and turn-in a bit early, so that the rear end is lightened too much for the corner. (That's right- weight transfer again!) When the rear end starts coming around, don't correct too fast. We want you to get the rear end out there, at least a foot or three! Recover by steering in the direction of the skid and rolling on enough throttle to restore weight balance.
- Four-wheel drifts. Generate a small amount of over-steer, only this time set the car up to use throttle-steer to control the slide. Roll on enough throttle to keep the front end sliding too, so that the car drifts around the corner. This is not the fastest way to corner, but it is a great way to teach the fine art of throttle control!
- Spins. Yes, we want you to spin. On purpose. Under control. Spin the car to a stop midway around the turn. Remember- IN A SPIN, BOTH FEET IN! Any time you reach the point where the car is going to spin -- and that means more than 90 degrees to direction of travel -- push the clutch in! Otherwise, if the car goes backwards in gear you can get some serious engine damage!
The large oval will be used to practice heel-and-toe technique, in addition to the small oval exercises. The focus is about half on heel-and-toe, half on the other skills.
Its a common misconception that heel-and-toe downshifting is about braking. Its not. That idea came from olden days when brakes were poor and prone to fade and failure. Today's brakes are so much more powerful and reliable, and engines so much more expensive, that its foolish to use your engine for braking. Why then is heel-and-toe downshifting important? Because it helps to control weight transfer!
Downshifting without matching engine revs to the lower gear will cause the car to lurch, upsetting its balance. A real bad downshift may upset things enough to cause a skid or spin. But smooth shifting is important even in regular driving, if only because it increases the useful life of expensive drive-train components. Heel-and-toe technique is essential to smooth downshifting.
Here is the way to heel-and-toe downshift, step by step:
- Start braking, squeezing on the brakes with the ball of your right foot.
- Move your hand to the shift lever and position your foot on the clutch, to be ready to shift. Continue braking.
- Now push in the clutch and shift. As your clutch goes in, pivot your right heel and roll the side of your right foot onto the throttle.
- Squeeze on the throttle with the side of your right foot, and rev up to just above where it was in the higher gear. Continue braking as you shift, let the clutch out and roll off the throttle.
- Pivot your foot back to finish braking after a nice, smooth downshift.
Done properly, heel-and-toe downshifting can be so smooth you hardly feel it. One key to this is learning to match engine revs to your gear and speed. The more you do it, the better you will get. You can even practice while droning along on the morning commute! While cruising along at 60 mph in 5th, practice shifting from 5th to 4th to 3rd, back and forth, while maintaining a constant speed. This does not involve braking but it will help develop a feel for the car, ultimately enabling smooth downshifts without looking at the tach, or even thinking about it. It will just become automatic.
Secrets of Smooth Shifting
With any luck, this will not remain a secret for long. The secrets of smooth shifting are: throttle control and rhythm. Up-shift or down-shift, it doesn't matter. The gas pedal is not an on/off switch. When preparing to shift, don't just suddenly lift completely off the throttle. Lift smoothly, at a rate and in an amount appropriate to the rhythm of the car. Then when ready to let the clutch back out to complete the shift, bring the revs back up again by using throttle that suits the rhythm of the car.
A little more about the rhythm thing. Each car has a transmission that shifts well at a certain rate. Try to shift faster and it feels forced. Hard on the equipment and the chance of a missed shift goes way up. Find the right rhythm of clutch-shift-clutch though, get into that rhythm, and you will be smooth and consistent. And that equals fast and safe. Likewise, each car has an engine that revs up and down at a particular rate. Get into that rhythm too. Then bring it all together and groove on the sublime smoothness of it all.
Heel-and-toe downshifting practice
- Heel-and-toe. Execute heel-and-toe downshifts while lapping at a moderate pace. Concentrate on smooth shifting. This goes for up-shifts as well as down-shifts! Drive the late-apex line, keeping the speed down enough to allow full concentration on smooth shifting.
- Braking and cornering. Increase the pace, with emphasis on setting the car up on the desired line, as you become more comfortable with heel-and-toe. Everything listed above for the small oval applies here. When you have mastered heel-and-toe, and with your instructors approval, proceed to practice those same 7 skills here.
You've just completed a very demanding course in the basics of car control. You've learned some new skills, becoming a better driver in the process. Now don't let it all go to waste! Come on out and try Autocross or Drivers Ed. Or come back and try Skills Day again, to see how much better you do. Until then, drive safely, drive well, and most of all -- drive your Porsche!