As part of my driver education in a 911, I am learning what happens when you accelerate towards a turn point, lift off at around 45 mph in 2nd on a wet tarmac ( airfield - large space) then turn in sharply.....OK what you experience is a spin. ( lift off oversteer, back wheels lost grip)

If you let go of the steering wheel immediately after the turn in, it spins itself rapidly to full lock and also unwinds itself. If however you continue to hold onto the steering wheel you do nothing useful. Obviously there is a right thing to do, probably a combination of getting back on power and corrective steering. You got time as spin seems to take about 3 seconds.

I've read plenty about how transfer of weight loads up front at same time as unloading back, and how tyre grip varies with weight load and slip angle.
I've not seen any good explanation anywhere of what causes the steering wheel motion reaction eg a series of diagrams of wheel direction and car direction. Can anyone explain what is happening ?

 

Well i guess i'll take a shot at answering your question. The main reason your steering wheel turns in the direction of the drift is the side slipping of the front wheels. As you start to spin, the car is pointing ~10-45 degrees away from your actual direction of travel (disregard your position in the corner). So at that split second as you let go of the steering wheel, the front tires are pointed away from where they are going, and logically a wheel wants to roll so it oreints itself to roll.
Same thing happens on a bike, once you're rolling, the bike wants to go straight.

If you let the front wheels correct the spin, by letting go of the wheel, you will probably end up spinning in the opposite direction b/c it will over correct. Its pretty hard to correct fast enough for severe lift throttle oversteer, you just need reeeeaaally quick hands.

Sometimes in autocrosses i will let go of the wheel for a second when the car gets close to spinning, but i let the wheel slide through my hands and catchit before it overcorrects.

-Phil

 

thanks Phil - since I posted I got a toy car out ( actually a 911 Speedster with 'live' suspension and steering ( ackermann, half turn of wheel being full lock ! ) and played with it on the tabletop to figure out what happens. my wife thinks I am reverting to childhood.
I think what you suggest is good, ie letting the car feedback some steering movement but taking over before it winds too much on. I guess if car is still moving forwards there is some castor action - ie self centreing - based on steering geometry ( toe -in, camber).

 

in a spin you should get your wheels pointed straight relative to the car, this will result in a more predictable spin. Plus often it will stop the car from spinning beyond 180 degrees and you stay on the track and roll backwards to a stop. Very predictable for those around you.

This is why most teach keeping you hands at 3 and 9 on the wheel so in a spin you can just turn the wheel to straight, if you shuffle steer, it is much tougher to instinctively get to straight

Jim

 

Yes, as long as your hands are off the wheel, may as well use them to cover your eyes...

That way you won't have to worry about which way the wheel is spinning or how long it takes it to do so...

 

'If you let go of the steering wheel immediately after the turn in, it spins itself rapidly to full lock and also unwinds itself.'

I may be wrong but I am under the impression that this 'unwinding' is due to castor.

 

LOL ! might try that if entry speed was above 120mph which was the case the last time I left the track, not a spin but more of a 'straight on ', you sit there a 'passenger' watching the tire wall coming up , hands on wheel, wheels on grass, zero grippo.

The exercise I am doing is to deliberately induce a spin at low speed ( 45ish) in a big space and try to get a feel for what is going on. wet conditions make it easier. Its an enlightening experience as all my past years of driving have concentrated on avoiding spins / slides. Starting with zero corrective input - no throttle no brake no hands on wheel.....then adding these as required !!!

 

Does

a) my driver education in a 911,

have anything to do with,

b) entry speed was above 120mph which was the case the last time I left the track, not a spin but more of a 'straight on ', you sit there a 'passenger' watching the tire wall coming up , hands on wheel, wheels on grass, zero grippo.

perhaps I`ll see you soon.

 

Hi Tony, the answer to your question is a definite maybe. I wont be out on track again till next March , meantime am subjecting the 996 to some challenges. Have you got any pearls of wisdom on the art of rotating a 911 ??

 

My personal favorities that may not have ben covered by Don are;

a) getting close behind someone at a slow speed 2nd gear corner and turning inside them on the exit of the corner whilst simultaneously giving it the full moo on the throttle, and

b) changing down from 4th to 2nd on a third gear corner just after you`ve turned in without heel and toeing.

both will generally help you rotate the car, especially in the wet.

 

Yes, I confess I've released the wheel to let it unwind and the move arrested my spin. I don't think I've ever read about this technique but as a number of you have mentioned, caster is probably the reason the front wheels turn out to save the car.

I've only done it a few times and once in the wet. It was entirely instinctive and I've felt guilty about it ever since. It's comforting to know I'm not alone.

 

Hi Joey, I always follow your posts with interest ...the exercise I have described is ( I think) meant to give repeated experience of the feel of the back end going...the full sight + sound + gut feel. Where it will lead to is deliberate use of roll oversteer to rotate car in a turn....controlled of course

 

Thanks, Oldtimer, for the props.

This sounds like a great exercise. I actually tried go karting for the first time a few weeks back and realized the value of being able to practice controlled techniques in a relatively safe environment.

These carts did maybe 30 mph but if you lifted a bit and cranked the wheel hard into a corner, the tail would step out which was then easily controlled with some gentle throttle inputs. After a while, I was able to "balance" the inputs and slide around the corners like some WRC racer.

The problem with our cars is that they stick so damn well that you need to carry some pretty good speed to loosen things up. I may lift occasionally if I find myself running out of track, but the "balancing act" is not something I practice often at the track--not at 50+ mph and with all that traffic.

I'd sure love to toss my car around like that go kart, though. Yes, it's probably not the fastest way around the track nor is it conducive to tread life, but it's a heckuva' lot more entertaining than that relentless search for the perfect line.