Skidding Advice

[zcacogp]

I can only assume I was traveling too quickly, given the conditions and my level of skill. Had you tried to persuade me of this 5 minutes before It happened, I would have vehemently denied it. However, 40mph on a wide, open, empty A-road in Warwickshire is perhaps made a little more tricky by 4 inches of snow on the ground, and more of the stuff coming down thickly.

Thankfully, there was no-one coming the other way when I negotiated the sweeping left hand bend. Because at that point the rear end of the car decided that following the front was altogether too tedious and the taillights decided they would prefer to arrive at the destination before the headlights. The car span gracefully to the right, and once it was more than slightly underway I was no more than a passenger, although a passenger who had the sense to let go of the steering wheel, dip the clutch and NOT to brake.

Someone was watching out for us because not only were there no other cars in sight, the pirouette took us onto a grassy verge and we didn't have quite enough speed to fall into the ditch beyond it. I was deeply, deeply grateful that while the front of the car was well over that ditch, the front wheels were two inches short of it, and we had missed the last road sign by four feet or so. Getting on our way again took no more than putting the car in reverse, backing back onto the carriageway and driving off again (at not more than 20mph this time.)

I was lucky. It was a nasty moment. (Mrs zcacogp had so many kittens we had to stop to let them out a little further up the road.) And while my S2 has bitten me three or four times in the last 6 years, this was the worst by some measure. Usually I can recover things by dipping the clutch and steering into the skid, but this time there was too much momentum, too much speed and no chance of bringing things back into line.

A salutatory lesson for me, for sure. What could I have done better? What advice do you have concerning 944's getting out of line? What can you do when the back of the car swings out - I am aware that the neutral weight distribution of the 944 (engine in the front, gearbox in the back) is what makes them so stable, but will also make them fiendishly difficult to get back in line once the back is moving in the wrong direction.

And another one; does the means of recovering from a skid differ depending upon what you are driving on? I am assuming not; the handling dynamics are the same regardless of what is underneath the tyres, although slippery surfaces will mean that everything happens at lower speeds than on more grippy surfaces. (This is disregarding factors such as differing behavior of different tyres in different conditions, if not every wheel is shod in the same rubber.)

Thanks for your input.


Oli.

 

[Copperman05]

I had a similar experience a couple of weeks ago when negotiating a cold, damp roundabout on the A414 in Herts, back end came round and momentarily I was staring at the central reservation and thinking this is going to be costly (note how I was more concerned of the car than myself[]) However nearly as soon as I came off throttle the back came back and I continued (nervously) on my way.

Both incidents being a typical example of driving too fast for the road conditons it seems. I was glad my reaction was the correct one, off throttle (or as in your case, clutch in) and steer into the slide, time on the skidpan for driver training at work taught me the earlier you notice the slide and the earlier you get 'off gas' the much earlier (and more safely) you can recover the skid.

I think at least you have found the boundary of what level of grip you have in such circumstances and you surely acted in the appropriate way, definitely much better than learning from the lesson but still paying for it. Something both you and I will certainly be thankful for.


Edd

 

[Mike_Pollock]

Glad you Mrs Z the kittens and the car are ok. (we have a couple of kittens too)
When there is no grip - there is NO grip, it is easy to use all of what little there is to build up speed over a given period of time (this tends to be true whatever level of grip!), the problem is that we tend to allow less time to slow or turn ( usually your brakes are better than the engine accelerates) and we also tend not to realise how much grip is required to deviate a tonne and a half of metal, human and cat!
I think the 944s fair better than most rear drive cars of their era, but as you say because of their inherent balance de clutching and steering into a skid, will usually work, if there is some grip.
Which is where I came in...

 

[Neil Haughey]

I have had a few spins on track, ISTR 2 of my 5 offs in race 3 at Silverstone last year were spins, would have to check the vid. What I can say is this; the car is pretty well recoverable as long as the angle of dangle is not to big, beyond that your going round or worse having a horrific tank slapper.

Honestly in the dry on track best thing is to put both feet down, clutch and brake. I did this testing at Mallory the other year had a massive spin going into to Gerrards braking too late too much speed (close on 3 figures). Its amazing how much speed can be quickly scrubbed going sideways on dry tarmac. Could honestly have destroyed the car in different circumstances but I had scrubbed enough speed whilst still on the tarmac that the car didn't travel too far once of it. Damaged my confidence short term that one but longer term did me the world of good as I just don't worry about crashing the car now.

 

[simdel1]

I generally follow a simple rule - stop doing whatever it was that caused the problem.

So, if the back is coming round because of too much throttle, get of the throttle and steer into the slide. If the back is lost under braking, reduce braking pressure and steer into the slide (or effectively stop steering into the corner). If you're steady state (steady speed, steady throttle, constant steering angle) then back off enough to quell the possible wheel spin, but jumping off the throttle can throw the weight of the car forward and cause the rear to slide even more (lift-off oversteer). I apply this rule in the dry, wet or snow. the dynamics of the car change little...only the speed at which everything happens

Of course, as Mike says, if there's no grip there's no grip and you are just a passenger.

 

[Lowtimer]

I am aware that the neutral weight distribution of the 944 (engine in the front, gearbox in the back) is what makes them so stable, but will also make them fiendishly difficult to get back in line once the back is moving in the wrong direction.

It's not so much the neutral weight distribution as the high polar moment of inertia - the fact that there are widely spaced weight masses. This characteristic means it takes quite a bit to start it yawing, but then takes a lot to stop it yawing. On a 944 this means that avoiding a slide rather than correcting it is a preferable approach on a low friction surface.

And another one; does the means of recovering from a skid differ depending upon what you are driving on? I am assuming not; the handling dynamics are the same regardless of what is underneath the tyres, although slippery surfaces will mean that everything happens at lower speeds than on more grippy surfaces. (This is disregarding factors such as differing behavior of different tyres in different conditions, if not every wheel is shod in the same rubber.)

Speaking from personal experience, frosty and icy conditions are especially treacherous because conditions can be different under every wheel at the same time, and can then vary during the course of a slide. Changing road cambers, frozen puddles, drifts, unseen road bumps and potholes, and frost shadows are just a few of the mechanisms for this happening.

Cars do handle differently on low friction surfaces to how they handle on high friction surfaces. The effect of the throttle is greatly magnified, and momentum is a much more powerful force in comparison to anything the tyres can do. Also, on low mu surfaces you don't really get any of the generally helpful effects of weight transfer that we learn to use on our cars.

If you haven't driven your car much on a very low friction surface, it is very much worth taking it to a skid pan and spending a good long time playing with it there - it will help. But on the confines of the public roads, the best two things you can do are fit tyres good for the conditions, keep the speed down and think as far as possible ahead of teh car so that you do stay as far within each tyre's friction circle as possible.

I won't make it a Turbo vs S2 point, but a proper mechanical LSD changes quite a lot in these conditions, and can both help and hinder in different situations. I prefer to be with one, all other things being equal. That said, I am driving the BMW rather than the Turbo at the moment, partly to keep the salt off the Porsche but also because I have proper winter tyres on the BMW.

 

[will lyons]

Wow Oli. At least your all ok and hopefully didn't cause any damage to the s2. Realising what good friends I have here is giving me second thoughts of selling the turbo. Ohhhh hummmm. Watch this space. [:-]

 

[Super_Marv]

I find my 968 pretty useless in snow and ice. Near 50:50 weight distribution and RWD isn't very good on snow/ice, not enough weight pushing over the driven wheels.

Hate to say it, but perhaps for the 944/68 winter driver, winter tyres are the answer... [:'(]

 

[Lowtimer]

Huh? What's wrong with winter tyres? (Used in the winter, of course.)
In fact, what's wrong with anything that improves the performance of the car in a given set of circumstances?

 

[MarkK]

Hi Oli Glad you and Mrs Z are ok,these things happen and it's just good that you got away with it.
My suggestions are as follows
As someone just said...get a spare set of 16 inch wheels of your choice shod with Winter spec tyres,you can put them on in late September and take them off in March sometime,the difference is amazing I just got some this year and they work great in rain and lower temps,also as we just discovered today really good in snow,your traction and stopping in a 944 would be great with these.

If you are really interested in sideways technique,Porsche do driver days at the experience centre at Silverstone for a couple of hundred quid you drive your car on low friction surface,skid pan,and a thing that whips you sideways it is called YOUDRIVE and they welcome you in any brand of vehicle.
The facility is brilliant and a lot of fun,I think Vicky butler Henderson does some of the YOUDRIVE days...


Here is a link to me getting it as wrong as I ever have, I drove over some oil dropped by a GT3 under full throttle and completey lost it,was having a ding dong with a certain Mr F that hangs around on the 968 forum[]
It happened so quick it was like something snapped...
http://www.flickr.com/photos/hockeyshooter/6200816197/

 

[zcacogp]

ORIGINAL: Lowtimer

It's not so much the neutral weight distribution as the high polar moment of inertia - the fact that there are widely spaced weight masses. This characteristic means it takes quite a bit to start it yawing, but then takes a lot to stop it yawing.

... and, as such, will mean it is quite different to the behaviour of the modern neutrally-balanced Porsche, the Boxster/Cayman. I am guessing that they will spin significantly more easily, but be recovered more easily as well, on account of the fact that that all of the weight is in one block in the middle of the car.

ORIGINAL: Lowtimer
Speaking from personal experience, frosty and icy conditions are especially treacherous because conditions can be different under every wheel at the same time, and can then vary during the course of a slide. Changing road cambers, frozen puddles, drifts, unseen road bumps and potholes, and frost shadows are just a few of the mechanisms for this happening.

Cars do handle differently on low friction surfaces to how they handle on high friction surfaces. The effect of the throttle is greatly magnified, and momentum is a much more powerful force in comparison to anything the tyres can do. Also, on low mu surfaces you don't really get any of the generally helpful effects of weight transfer that we learn to use on our cars.

Two very good points, thank you. The varied nature of the surface may have been something to do with the spin (note - I stress the "may"; I don't know for sure.) I do know that I was travelling with constant (mild) throttle and the steering input was fractional, to the left. However the car started spinning to the right, so there must have been other factors at play there.

I take your point about the momentum:grip ratio changing dramatically on low grip surfaces. So, yes, handling does change when things get slippy - not just grip. And the weight transfer is another good point. Thank you - I hadn't thought about those factors like that before.

Will, thanks. Yes, no damage (although - like Edd - my first concern was damage to the car, not damage to Mrs zcacogp or me!), for which I am quite grateful. And, yes, you really shouldn't be selling your turbo - we'll all miss you!

Nothing wrong with winter tyres at all. They are dramatically much better than all-weather tyres in snow/slush/frost; I recall driving with some studded tyres in Reykjavik a few years ago, and they offered uncannily good traction on snow and ice (but were bordering on dangerous on wet tarmac!)


Oli.

 

[zcacogp]

ORIGINAL: MarkK

If you are really interested in sideways technique,Porsche do driver days at the experience centre at Silverstone for a couple of hundred quid you drive your car on low friction surface,skid pan,and a thing that whips you sideways it is called YOUDRIVE and they welcome you in any brand of vehicle.
The facility is brilliant and a lot of fun,I think Vicky butler Henderson does some of the YOUDRIVE days...

Ooooh, now that IS interesting - thank you. I'll google that ... could be a couple of hundred quid well spent. (Although I'm not sure I can afford it at the moment. [:'(])


Oli.

 

[Super_Marv]

ORIGINAL: Lowtimer

Huh? What's wrong with winter tyres? (Used in the winter, of course.)
In fact, what's wrong with anything that improves the performance of the car in a given set of circumstances?

Nothing wrong with them, no. If I used my car throughout winter, I'd buy a set of 16"s and bung some winter tyres on.

 

[MarkK]

Here's an idea that is less costly,what's the general on this,how about reducing tyre pressures just a little bit whilst it's slippery..?
The tyre would be less rigid,worth a try?Just a few PSI less nothing dramatic.
Someone raised a valid point about LSD,I think rear drive cars without LSD can be a bit hairy in lower friction conditions,one wheel can spin up quite violently maybe with weight off it in a corner?
(especially with the huge amounts of Torque an s2 spits out)[]

 

[simkin911]

Glad to hear that Mr & Mrs Z and Baltic Blue with linen are well despite the "scare".

 

[pauljmcnulty]

Ooooh, now that IS interesting - thank you. I'll google that ... could be a couple of hundred quid well spent. (Although I'm not sure I can afford it at the moment. )

Could have done it for £10 at the register day last year. Not trying to gloat here, just trying to point out that sometimes there are benefits to being a member! [&o]

I'm going to disagree with everyone here. Forget trying to be clever and explain it, there's no gain to be had from a formula that explains polar momentum over grip, extrapolated via tyre compound and ambient temperature, and gives you a safe speed in snow. The safe speed is VERY SLOW, as in, probably, walking pace. Any faster than walking pace and you can only blame yourself.

Last year we got stranded in the AWD Subaru. We found the limits, they are about 6" snow and 30 degrees incline on Conti sport-contact with near-limit wear. The missus' choice of tyre, if I'd known i would have changed them! [&:] This year we have winter tyres, and they are better; I got up the same hill today having bought the emergency Sunday Times. But, even with AWD and winter tyres, cornering on snow is walking pace or spin, only once did I achieve what the racing Gods would call "drift"! [&o]

I've not heard anyone who's got any real driving credentials, be that race, IAM etc., describe the 944 as anything other than incredibly easy to control through oversteer, unless it was inevitable oversteer. Not even an Fi driver can recover when he's terminally sideways, so the only answer is to slow down when conditions are that bad?

 

[peanut]

glad to hear that you are ok Oli. I've known for years that the rear end can come round and bite me so I am very cautious in the wet and I rarely drive in icy conditions in the S2.
I lost my Lux at 20mph on a roundabout and the car was written off. The front hit the central reservation and the rear hit the other barrier and we spun twice in heavy rain and diesel spillage.
You were very lucky.

 

[colin944]

2 things to say on this

1. Thankfully you Mrs Z and car are all ok .No harm done.I find in a slide situation my reaction can be very different depending if I was trying to get the car sideways or not.If it's intended then a bit of opposite lock and balance the throttle.If it is unexpected thenpanic feet off everything and steer into it.
2. Message for Will. Good man keep the car and stay on here.

 

[MarkK]

That's good sensible and fatherly advice!![]
I am in my 205 in the morning as it's quite good in the snow etc once rolling,I am praying I can get off my drive (slight incline) and then on to the main road as I need to open up work in the morning as my mrs gets the winter car for the kids run to school.
I have a Diesel BMW for work at the minute 530GT and I tried to move it today,fat tyres,too much torque and electronic aids made it impossible as I parked it next to the house and it kept sliding towards the bricks[&:][&:]
Hoping my phone weather prediction is right and it all is melted by rain tonite.otherwise it's all up to the little pug[]
In the words of Hill street blues opening bit "hey let's be careful out there!"
(Only 40s and above will remember that programme)

 

[Neil Haughey]

ORIGINAL: MarkK

Here's an idea that is less costly,what's the general on this,how about reducing tyre pressures just a little bit whilst it's slippery..?
The tyre would be less rigid,worth a try?Just a few PSI less nothing dramatic.

I am driving my old Rangie at the moment but that is pretty much how I run it, tyres down at the lower end of the pressure range. Feels a bit squirmy for the first mile but I reckon the movement makes them warm up much quicker, well at least that is how it feels as the car generally tightens up and grips really well after a mile or two even in our recent sub zero temps.