I was discussing a customer’s recent spins on track with him and I ended up writing enough about catching a slide that I thought I would share: (in addition to working at Forged I run a small driving school and instruct for all the _CA's - PCA, BMWCCA, FCA, SCCA, NASA, Chin, MVP, etc...)

As for getting the wheel back to the right angle, they call it CPR - Correct, Pause, Recover -

Correct - As the tail goes out (yaw angle increases), you have to Correct (put in counter-steer/opposite lock/lock). Honestly, this is usually the “easy” part. Most people intuitively steer into a slide and catch the “first” slide. That said, when you are really on the limits you sometimes need to put in a LOT of lock (often 180 degrees of steering wheel angle, also known as “crossing elbows”) QUICKLY. There have been a few videos circulating lately where someone new to the track counter-steers 1/8th of a turn of the wheel (45 degrees of lock) slowly and is surprised when they spin off the track. If you watch pros that are really “wheeling it” they often put in 90-180 degrees of lock almost INSTANTLY. I honestly think that the people that put in 45 degrees of lock and then go through a slow lazy spin that should have easily been caught might play too many video games with a wheel that only has 180 degrees from lock-to-lock. A real car usually has 540 degrees from lock-to-lock.

Pause - you have to feel for the yaw to Pause. Basically, as the tail swings out (increasing yaw angle), the yaw RATE (speed that the yaw angle is CHANGING) goes from near zero to a lot in a hurry. *IF* you are going to "catch" the slide, you should be able to feel the yaw RATE (how fast the yaw ANGLE is increasing) slow, and then stop or Pause. This will be at the largest yaw ANGLE, but as soon as the yaw stops increasing, your yaw RATE is zero, or Paused. A drifter tries to hold the angle here at the max yaw angle (with near zero yaw rate). A road course driver wants the yaw angle to reduce. The trick is to get the yaw angle to reduce under control and stop at zero yaw angle.

Recover - If you have "caught" the slide, your yaw angle should begin to reduce. As the car swings back toward pointing in the same direction as it's traveling (zero yaw angle) you must get the wheel back to straight, or Recover the "lock" you put in. This is really the most important part; you *MUST* get the steering wheel back to straight before the car gets back to straight (zero yaw angle). If the car swings back to zero yaw angle and you still have the wheel pointed into the slide, the momentum of the tail will just keep swinging to the opposite side like a pendulum. Most people catch the first slide; it's being too slow on the Recovery that makes them snap in the other direction.

It's generally MUCH better to recover too quickly, than too slowly. If you recover too quickly the yaw RATE (remember, rate is how fast yaw ANGLE is CHANGING) will slow or even stop - when the yaw RATE is zero, the yaw angle isn't changing. Ideally the yaw angle stops as the car is straight, but if you recover too quickly the yaw rate might go to zero while there is still some yaw angle in it. Usually the yaw angle will begin to increase again - another tail-slide in the same direction it was. Putting a little more lock in it should again slow the yaw rate - feel for the Pause, and then you can Recover again. This is MUCH better than having it whip back and forth.

Siegel

 

We had discussed throttle control in a previous e-mail...

There are generally two types of over-steer (tail-out) - trailing-throttle (off throttle) and power-on (on throttle) oversteer.

Trailing-throttle oversteer is generally on the way INTO a corner. Braking or being off the throttle transfers the weight down onto the front tires, and up off of the rears. This increases grip in the front (good for turn-in) and reduces grip in the back (good if you are trying to get it to rotate into the corner, bad if you didn't want the tail to slide). In this situation you need to get some weight onto the rears to help them grip. Generally you will reduce the braking, or even give it a LITTLE gas. With the AWD, a little throttle will also let the front tires pull the front toward straight.

In a low-speed corner it's often good to get a little rotation - you will sometimes be braking / off-throttle all the way to, or even past the apex.

In a mid-speed corner you will usually be going to the throttle at or before the apex.

In a high-speed corner it is important to be back on the throttle (usually before the apex) to balance the car.

Power-on oversteer is another story. Power-on oversteer is from asking the rear tires to do more accelerating than the blend of cornering and accelerating will allow.

This is known as the "Traction Circle." You have a circle with acceleration and braking on the x axis (6 o'clock to 12 o'clock) and cornering on the y (9 o'clock to 3 o'clock). The amount of grip available from a tire can be represented as the outer edge of the circle.

At max braking there is nothing available for cornering (imagine having all 4 tires locked, the direction that the front wheels are pointing doesn't matter, you're sliding on 4 rubber nubs). If you had enough power, at max acceleration there is nothing left for cornering (taken to the extreme, the front tires would be in the air). At max cornering there is nothing left for acceleration or braking (either will cause one end to slide out).

As soon as you reduce any inputs from there absolute max, you can begin to "blend" them. There is LOTS of room to blend braking and cornering (trail-braking), and cornering and acceleration (getting off the corner).

Mid-corner there is generally a section (sometimes VERY short) where you are at max cornering and "neutral throttle" (no accel or decel). As you add power on the way off the corner, if you ask for too much acceleration for how much cornering grip you are already using, you have "asked" for something outside the traction circle. It can't do that, so there is not enough grip to keep that end of the car on your desired line.

As the tail slides, reducing the throttle will bring your "request" back inside the traction circle. Once the requested grip is less than the required grip, the yaw rate should begin to reduce... See above

Siegel

 

Should add this information to the FAQ.

 

One small suggestion:

 

I guess I should be more clear, by Recover, I've always taken that as "Recover the WHEEL" - or get the steering wheel back to center.

It's better to get the wheel back to straight too fast than too slow. If you get the wheel straight too fast, the car might not get all the way back to straight, and you might have to put a little counter-steer back into it. If you get the wheel back to straight too slow, it tank-slaps back the other way.

If you take "Recover" to mean getting the CAR back to straight, yes it's absolutely better to have it come back to straight slowly.

Siegel