A Treatise on Spin Control

Sharif@Forged

This was posted by Scott Siegel who works for Forged, and is also a well know driving instructor. If you ever get the chance to have this guy ride shotgun with you around a track, you should jump at the opportunity.

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.

Thanks,
Siegel

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Sharif@Forgedperformance.com
General Manager/Certified Tuner/NASA-PCA-BMWCAA Instructor
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RCZ

Nice Siegel... Everything makes perfect sense to those who have been there and know the situation. Anyone who hasn't will understand NONE of this haha. Also, when the time comes for someone to make use of this, knowledge flies out the window and everything becomes instinct. For that reason, I think the only way to really master catching a slide is a closed off, wet, empty parking lot/skidpad/track. If you can get on some snow, even better. Its all the same, just slow motion. Practice, Practice and more practice.

Very cool explanation though, thats the theory!

IMWEZL

Or just autocross with VDC off.

travisjb

great post, thanks

+1 on autocross... this came up recently on another thread and it is a structured and low-risk way to practice car control... some clubs have 'autocross clinics' too, which are great for beginners

I remember on my old boxster, it was so easy to 'catch' an excessive yaw angle (or drift or slip angle or whatever) but an absolute bitch trying to get / keep control on the way back... there was almost always a big reverse oscillation, then another, etc despite getting the steering wheel back to 'zero'... whereas with the Z, I can hang it out all day long and find it easy to manage... the mid-engine car was great for being at the limit, not as great for recovering beyond the limit... didn't help that it was an open diff of course

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Sharif@Forged

Agreed....^^^Very safe way to practice, as it's a skill that is very difficult to teach.

__________________
Sharif@Forgedperformance.com
General Manager/Certified Tuner/NASA-PCA-BMWCAA Instructor
JRZ RS1's Available NOW...PM me
Cobb ProTuner, Uprev ECU Flash, FCON Vpro, Haltech, Motec Certified

bullitt5897

Great Post Scott!!! I know exactly what your talking about coming from an s2k world we have to act fast to catch that spin. The 370z is so much easier to catch the spin. I cant wait to get back on the track with you this time you got to get that subaru on the track

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