Nissan 370Z Tech Forums banner

1 - 9 of 9 Posts

·
Registered
Joined
·
2,946 Posts
Discussion Starter #1
Adhesion

Your car sticks to the road with four small contact patches from your tires. Each is about the size of your fist. Tire inflation changes the contact patch as does vehicle weight transfer from braking, accelerating or turning. What your suspension is doing to your tires determines how much adhesion you have.A tire has only so much adhesion to give. A tire past its limit of adhesion is either spinning, skidding or sliding. Once a tire is to this point it's of no use to you and you're no longer in control.

Car dynamics

When you brake or let off the throttle weight transfers to the front of the car. This increases the size of your tires' contact patches in front and lessens them in back. This means you have more traction in front than in back. So your steering feels great, but the rear end is more likely to lose traction. When you accelerate weight transfers to the back. This decreases the traction of the front tires making the car less responsive to steering inputs. You have extra traction in back.
Going around a corner transfers weight to the outside tires. So going around a corner while braking transfers most of the weight to the outside front tire.
You only have "x" amount of adhesion from your tires. How much do you need for turning, how much for braking or accelerating? Plan ahead for what you require from your tires!

Understeer (push) - The car under performs to your steering inputs. The front tires are skidding; they've passed their limit of adhesion. The front tires can't respond to your inputs. The car wants to continue to go straight

Oversteer (loose) - The car over performs to your steering inputs. The rear tires are skidding. The back end wants to come around.

Most cars are built to understeer at their limits. Sliding in a straight line is preferable to spinning and the natural reaction to a situation like this is to get off the gas. This transfers weight to the front giving those tires more traction and reducing the understeer.
Neutral handling or "drifting" - This is when all four tires will lose traction at the same time so the car drifts instead of plowing straight ahead (understeer) or spinning (oversteer). This is the ideal situation for the race track. Some cars are easier to set up than others. Car like the mid-engined Porsche Boxster or Toyota MR2 or an RX-7 (front engine, but it's behind the front wheels) are easier to set up for neutral steering as opposed to a Mustang or a FWD car.

Skid Control

Proper hand position on the steering wheel either at the "9 and 3" or "10 and 2" position gives you good control of the wheel and makes it easy to determine when you have the front wheels pointing straight ahead. If you are trying to recover from a spin it's good to know when the wheels are pointing straight ahead because when you regain traction the car will head off into whatever direction it's pointing at the time.
If you skid look where you want to go. If you're looking off the side of the road chances are you will mentally and physically steer there. Steer in the direction you want to go. This is where looking in that direction helps! If you lock the brakes you lose steering control. "If in doubt both feet out", that is don't use the gas or brakes if you don't have control of the skid.
If you lose it and spin then "both feet in" (the clutch and brake). You'll stop sooner and slide in a straight line. If you are out of control, but try to regain control (that is, regain traction) guess what happens when traction is restored? The car takes off in whatever direction it's facing when traction is regained--like into oncoming traffic. Once you've lost control lock up the brakes and slide out of the way!

Braking

Brake in a straight line. Remember the part about braking shifting weight to the front and away from the rear tires; plus turning transfers weight to the outside? It's too much to ask of your tires to brake and turn at the same time if you're near the limit of adhesion.
Trail-braking is a more advanced technique to help bring the rear end of the car around (oversteer) in a controlled manner when entering a corner.
The best braking is just short of lock up. Lock up means the wheel is no longer turning; it's skidding and it actually takes longer to stop. If the front wheels are locked they will not respond to steering inputs because they've passed their limit of adhesion.
 

·
Registered
Joined
·
2,946 Posts
Discussion Starter #4
You want to straighten out the corner. The larger your arc through the corner the faster you can go through.

Braking. Point "B" in the picture is the braking zone. All braking should be finished in a straight line then your foot is back on a constant throttle before turning into the corner.

Turn in. Point "I" is your entry into the corner starting at the outside edge of the track. You should have a steady steering angle and a constant speed to the apex.

Apex. Point "A" is where you are closest to the inside edge of the corner. The proper apex is usually not in the exact middle of a turn, but a little "late." Hitting the apex right determines how fast you can exit the corner. From the apex you should begin unwinding the steering and adding power as you now have available adhesion for accelerating. If you think about the Car Dynamics and Adhesion information above you will see that accelerating out of the corner will be an understeer situation. You won't require much steering input to "push" the car towards the outside of the track.

Turn out. Point "O" is the exit from the corner on the far edge of the track. At this point the steering wheel should be straight and you should be on full power.
So essentially, you take a corner "outside-inside-outside." That is, you start at the outside edge for the turn in point and drive an arc to the inside near mid-corner, the apex, then drive to the outside again for the turn out.
If you turn in too late you won't be able to straighten out the corner as much as possible so you will be slower through the corner. If you turn in too early you'll hit the apex too early and you'll run out of track before you get to the turn out (you tried to straighten the corner too much.) As you can see turning in too early can be bad because you can get yourself in a situation where you have to turn in more after the apex where you should be unwinding the wheel and accelerating. If you're at maximum adhesion you have nothing left for turning and you will go off the track or spin trying to adjust. It's important to know that you hit the apex correctly. When starting out always turn in a bit late and apex late until you learn the corner.

If you have a series of curves to go through (S-curves) you want to be sure you're set up correctly for the last one so you can have the most speed going onto the straight at the end. This means you have to "give up" the first corner to get set up correctly for the last. This usually means very late apexes for the earlier corners so you have proper turn in for the next.
 

·
Registered
Joined
·
2,946 Posts
Discussion Starter #5
and finally


Some common beginner's mistakes

1. Turning in too early. This happens because you think you're going to get through the corner faster because if you turn in early you're not turning in as tight, but by doing this you wind up sliding through the apex to turn out. It's gotta be "slow in fast out."

2. Entering the slower corners too fast, then scrubbing off speed as you squeal all the way through the turn. This may sound like #1 above, but it's not. Most new drivers are too fast into the slow corners, but too slow through the faster ones.

3. Braking while turning in. It's best to brake too early then be back on a constant throttle well before turn in. Then on later laps you can slowly move up the braking zone closer to the turn in. This is especially good for the faster corners.

4. Not looking ahead to your next reference point (apex, turn out, etc). Know where you're going next to prevent having to make any mid-turn corrections. Just before the turn in pick up the apex. When you get almost to the apex look for the turn out point. Hand-eye coordination is what's going on here. Look where you want to go.

5. Not using the whole track. Most of the first-timers quickly forget about hitting the turn in, apex & turn out cones. You shouldn't have more than a couple of feet between your wheels and the berms on the higher speed corners. Many inexperienced drivers will be eight feet away. On the slower ones actually being slightly on the edge of the berm may be good. When you pass by one of these points take a quick glance over to see how close you are. Sometimes having a rider or someone following helps critique this.
6. Coasting. Always be either on the brake or the accelerator. Coasting means indecision because you haven't planned ahead well enough.

7. Trying to be fast right away. Start off by worrying about technique & smoothness. Speed will come later. If you start off wanting to be the fastest car out there then after a couple of times at the track you'll get frustrated by a lack of progress in your times. Inexperienced, fast drivers are usually very unbalanced, choppy and very rushed in the driver's seat.

8. Frustration because even though you are doing everything you've been told you feel like you're getting slower. If you practice doing it right then after a few open-track or autocross events you'll come to a point where you think you've gotten slower, but you're actually faster. That's because if you're really smooth and anticipate your next moves then this lack of hurriedness on your part will seem like you're slow, but you're actually just better!
 

·
Premium Member
Joined
·
5,911 Posts
Originally posted by LBSOHK@Sep 5 2004, 01:47 PM
2. Entering the slower corners too fast, then scrubbing off speed as you squeal all the way through the turn.  This may sound like #1 above, but it's not. Most new drivers are too fast into the slow corners, but too slow through the faster ones.

3. Braking while turning in.  It's best to brake too early then be back on a constant throttle well before turn in.  Then on later laps you can slowly move up the braking zone closer to the turn in.  This is especially good for the faster corners.

To build off of these two points, remember, it's easier to gain speed coming out of a turn than it is to slow down during one
 

·
Registered
Joined
·
209 Posts
I have the book Speed Secrets and I highlited some good points. Thought i would share some.

Without track discipline, a driver will not be successful. Undiscipline drivers crash alot. They are not consistent. They do not give good feedback on what the car is doing. They are hard on the car, and therefore do not finish a lot. They are not good racers.

While driving, make note of the vibrations and feedback through the steering wheel. Does the steering get lighter or heavier as the tires slide more? Make note of the sound comming from the tire. Do they make more or less noise as they slide more? How much noise do they make before they slide too much?

The tighter the radious, the later the apex; the larger the radious, the earlier the apex. In simple terms, a slow hairpin will require a later apex than a fast, sweeping turn.

The more you try to keep the car away from the wall at the exit, the more likley it is you will end up hitting it. Unwind the steering and let the car track-out as cloase to the wall as possible.

Drive in your mind before driving on the track.

Delete you expectations. Focus on your possibilities.

Every inch of track you are not using is costing you speed. You paid for it, so use it.

The less change of speed in a corner, the faster you will be.

Sensory input and awarness are the keys to driving fast.
 
1 - 9 of 9 Posts
Top