|A Guide to Autocrossing|
A Guide to Autocrossing
By The Golden Gate Lotus Club
Autocrossing & Fun
Q: Why autocross?
A: Because first and foremost it's FUN!
Q: But, do you learn anything?
A: You can learn to be a more competent, safer driver.
Q: How can I become a safer driver by "autocrossing"?
A: Autocrossing is a low speed, timed driving event. Cars are allowed onto the "course" one at a time. Drivers can test their skills and the capabilities of their cars in a safe atmosphere under controlled conditions. By experiencing their own limits and those of their cars, the driver learns how to control and avoid unsafe situations.
Q: What do I need to autocross?
A: Very little. A car in good mechanical condition; free of fluid leaks, good brakes, seat belts, tires in good condition and a helmet.
Q: What exactly is an autocross?
A: Quite simply an autocross is a low speed time trial. Cars are timed over a course laid out on a large paved area (free of obstructions). The course is defined by safety pylons and chalk line, thus off course excursion cause no physical damage. Cars are timed one at a time, there is no wheel to wheel racing.
Car preparation can take on many levels from the casual autocrosser to the avid, serious autocross competitor. At the beginning level simple safety oriented items should be checked. These are typical items that would be checked in the normal course of daily driving.
1) Check tire pressures. Typically over-inflate to 6-10 lb. over factory recommended settings.
2) Check engine oil, brake fluid and coolant levels. Top off as needed.
3) Check battery tie-down. Be sure the battery is securely fastened to the car.
4) Check brake linings for wear. Check for firm brake pedal.
5) Check for fluid leaks.
6) Check your shock absorbers by the bounce method.
7) Check your steering for looseness.
8) Check your fuel level. Have at least 1/2 tank full.
9) Check your tires for condition and tread depth. Cracking, odd wear patterns, baldness of the tires are indications of excessive wear and weathering. Replace tires as needed.
10) Remove all loose objects from your trunk and from within the passenger compartment.
11) Check condition of seat belts. Look for fraying and excessive wear. Check seat belt mounts.
12) Remove wheel covers and hub caps.
13) Check lug nuts for tightness. Tighten to proper torque.
Correct preparation of the driver is essential for maximum performance. Like any athletic endeavor a driver that is well rested and in good health is more alert, has superior reactions, and can perform at full potential.
1) Get plenty of rest the night before.
2) Eat properly.
3) Drink water, don't allow yourself to become de-hydrated.
4) Wear comfortable clothing.
5) Wear comfortable shoes, with low heels and flat grippy rubber soles.
6) A helmet that fits properly, snug, but not too tight. Z.90 or DOT specification or better, in good condition.
Sitting In The Car
It may sound silly, but many drivers do not sit behind the controls of their cars in a position that allows them to comfortably control the vehicle. Often they are too close to the steering wheel, or too far away from the pedals. Find a position where simultaneously:
1) When full depressing the brake your knee is slightly bent. (by adjusting the seat.)
2) When holding the steering wheel at 9 and 3 o'clock there is about a 45° bend in your elbows. You can comfortably reach the top of the steering wheel without stretching or lifting your shoulder blade off the seat back. (by adjusting the rack of the seat back.)
3) Your back is comfortable and well supported. You are able to move your hands on the steering wheel completely around without straining.
4) You can adjust your seat belts so you feel secure and held tightly in position. (A trick is to shove a wad of folded paper or cardboard into the take-up reel to hold the seat belt in a tight position.)
Turning On A Long Corner
There are two types of long corners; 1) Long constant or nearly constant radius corners and; 2) tight 180° U-turns. First long constant radius corners: These types of corners can be treated like two corners, a corner off a straight leading immediately into a corner onto a straight. As such the entry is taken as described previously for a corner at the end of straight and the exit as a corner leading onto a straight. Thus, an early apex is used in the first half, the car travels to the outside edge of the track in the middle of the turn and then while accelerating a late apex is used during the corner exit.
The other type of long corner is a tight U-turn. Typically autocrossers call these "give-up" corners, meaning they are the type of corner where lots of time can be lost, but extremely difficult to make up any time. In the business world management might refer to these corners as "high risk", lots of downside, but little upside. So, the best course of action is to treat them conservatively. Brake early, staying to the outside of the course, stay wide as if you were going to do a very, very late apex.
Turns Between Turns
Turns between turns sounds rather silly, but these corners are those that tie a series of corners together. Properly call transitional corners, there is only one key objective to accomplish in these corners. That is to keep the car balanced and in position to enter a corner leading onto a straight. Thus, the driver could apex early for what intuitively appears to be an late apex corner in order to be on the very outside of the track at corner exit (turn-out).
Turning Off A Straight
The objective is the opposite of getting onto a straight. At the end of a straight the driver wants to carry and maintain speed for as long as possible. To achieve this the driver alters the driving line from a constant radius to one where the first half of the turn is straighten out and the second half is taken as a sharper turn.
Approach the corner at the end of a straight from the outside edge. Apply the brakes and slow. At the Turn-In point begin to steer into the corner while simultaneously releasing pressure on the brake pedal. The more you turn-in the more you release the pressure on the brakes. Clip the inside of the corner before the mid-way point. Still slowing, you now turn-in harder (remember to continue to release brake pressure).
This may seem like the most simple thing to do in a car. You want to go fast, right? So, just mash down on the throttle as hard and as fast as you can with your right foot! Right? Nope! Doing that will create a plethora of reactions from your car. The dynamics of a car follow the irrefutable laws of physics. So, when you mash down on the throttle, what happens?
a) The driving wheels may lose traction.
b) A portion of the car's weight shifts to the rear. This unloads the front tires. Thus the front tires will lose traction and they have lose some of their capability to change the direction of the car. To maximize the overall traction available a driver must try to keep the car "balanced". By balanced it means keeping the car's weight as evenly distributed on the four tires as possible.
So, does this mean accelerating like that little ol' grandma from a stop light with all the traffic back up behind her honking? No. But, it does mean that as a driver you squeeze the throttle down smoothly, yet quickly, but not faster than the engine can take more air/fuel mixture.
The benefit of this method is keeping the car from jerking, and instead staying relatively level, with as little weight transfer as possible.
Similar to accelerating, braking on the surface seems simple. Want to stop in the shortest distance possible? Well, stomp on the brake pedal with all your might! And, what happens? The nose of your car dives into the pavement, the wheels lock-up and your tires effectively become four blocks of black rubbers sliding over the pavement belching gray smoke.
If you've ever watched Indy or Formula 1 racing on TV you might have noticed that usually the drivers don't go smoking into corners. In fact if you see a puff of smoke from even one of their tires while being challenged by another racer, they immediately get passed!
So, the lesson here is brake, brake hard, but not so hard as to lock-up the wheels. This is call "Threshold Braking". It's braking a the point where your wheels are almost ready to lock-up, but they're still spinning every so slightly.
To execute this you treat the brake pedal as if there were a raw egg between your foot and the brake pedal. So, you ease the brakes on by adding steady pressure until you feel that you're at the threshold of lock-up. This method will accomplish three important things: a) Because the wheels are still spinning you will retain steering (blocks of rubber sliding over pavement can not change the direction of you car); b) You will minimize weight transfer to the front. Thus the nose of your car will not suddenly dive for the pavement (instead it will "squat"); c) Because the nose of your car stays more upright the front suspension of your car remains closer to its optimal settings and thus you retain more traction.
First, let's discuss how to hold the steering wheel. In car cameras are wonderful, it allows the lay person to climb inside the race car with the driver and pretend we are there with them. Have you ever noticed how the race driver holds the steering wheel? It's not what we were taught in driver's training; 10 and 2. No, rather you'll see the race driver holding the steering wheel at 9 and 3. And, for good reason. With your hands in the 9 and 3 position you have the greatest amount of leverage to turn the wheel and you're less likely to get your arms crossed.
Turning the steering wheel begins with your grip. Avoid the "Death" grip, that is grabbing the steering wheel so tightly that your knuckles turn white. Instead hold the steering wheel firmly passing from the heel of your palm diagonally up between your thumb and index finger. Your fingers can gently wrap around the wheels and your thumb is pointed up (avoid wrapping your thumb completely around the wheel).
There a number of various methods to turn the steering wheel, but they essentially have one thing in common, you never cross your arms (this means that classic "hand over hand" method is avoided). Instead you can initiate turn the wheel by pushing one hand upward and pulling the opposite hand down. Then just before your upward moving hand reaches the top of the steering wheel you slide your opposite hand up to the top of the steering wheel, grip the wheel and begin pulling the wheel down. This creates a smooth steering motion. Now, as you begin pulling downward the other hand drops down to the bottom the wheel and you can use it to push upward. Repeat the motion if needed.
Most commonly drivers allow the steering wheel to "self center" to straighten out. This entails letting go of the steering wheel and allowing it to spin freely back to straight. Unfortunately, during that time the steering wheel is spinning freely, you the driver have no control over the direction of the front wheels or the car! So, better to "unwind" the steering by repeating the above in the opposite direction.
A straight is just that, straight. It is the place where a driver can travel the greatest distance in the shortest amount time. Thus the straights become the most important part of the track. Drivers prioritize straights in terms of their length, longest is the most important. Hence the race driver wants to get to full throttle as quickly as possible and hold full throttle down the straight and stay on full throttle as long as possible. Between the straights are corners.
Generally speaking the race driver attempt to straighten out the roadway, as much as possible. To do so the driver tries to use the largest arc possible through a corner. This entails entering a corner from the outer most edge of the pavement, then swinging into the inside edge in mid-corner and then allowing the car to drift to outside edge as the driver exits the corner. The most common mistake of a novice driver is not using the entire width of the track. Between the corners are straights.
Turning Onto A Straight
The objective of a taking a corner leading onto a straight is to begin accelerating as early as possible. To achieve this the driver alters the driving line from a simple constant radius arc to a driving line where the driver can straighten the later half of the corner. This is called a late apex.
Enter the corner from the outside edge of the track. Brake early, and complete your braking for the corner while in a straight line (before turning into the corner). Turn-in the corner a bit later than you might think, and initiate a turn a bit sharper than you might normally execute. Once the car is pointed into the corner begin feathering the throttle, and moving the car toward the inside edge. Now, begin adding throttle, unwinding the steering wheel and clipping the inside of the course (apex) just beyond the mid-way point of the corner. This is called a late apex. You should be at or nearly at full throttle. Continue unwinding the steering wheel and onto the straight.
Slaloms test the car's ability to turn from one direction to another; left to right; right to left. Typically the quickest way through a slalom is to be gentle with the throttle, do not abruptly lift or depress the throttle. Such throttle application will likely end in a spin or gross understeer. So, set the throttle and gently steer. Try to have the car pointed in the overall direction of travel at the apex of each slalom.
Apex Refers to the point or region where the car is closest to the imaginary center of the corner.
Balance Refers to the weight distribution of the car. A car that is balance has equal (or as near as possible) weight on each wheel.
Braking Point The point as which you begin applying the brakes.
Lock-Up Applying the brakes so hard that the wheels stop spinning.
Neutral A cornering condition where the front tires of the car are cornering as hard as the rear tires.
Opposite Lock A steering motion where you steering away from the corner in order to neutralize the rear of the car sliding away from the corner.
Oversteer A cornering condition where the rear tires are cornering harder than the front tires.
Threshold Braking The point under braking where the tires are just about to lock-up.
Traction The frictional force developed by the tires against the pavement.
Turn-In The point at which steering motion is applied to turn into a corner.
Turn-Out The point of corner exit where the car returns to traveling is a straight line.
Understeer The cornering condition where the front tires are cornering harder than the rear tires.
Wheel Spin The condition where the driven wheels have lost traction and are spinning due to throttle application.