Span 180 degrees today

[James]

I will give you the basic details and then go further into it as and when questiosare asked. It is such a short simple story that it shouldn't take long.

Today me and my wife were down in Dorset and driving back from a funeral to the wake to Corfe Mullen and eventually to Swanage. (We drove down this morning and returned this evening). Needless to say, it has been pi$$ing it down all day, and I managed to achieve my best MPG ever today on my way down as the spray and conditions were so bad. (I am hoping this coupled with where we were going builds an idea of how I "wasn't" driving ).







Anyway, at a roundabout whereby I take the 2nd exit, positioned at 2 o'clock (worth noting a regular route for us), I had scrubbed off a load of speed having reached the roundabout from a NSL DC. It was particularly wet and know the RAB has an ever so slightly degenerated surface at points around it. But in general it is your normal, concrete RAB in god condition.

Anyway, I remember slowing right down and coming off the brakes as I entered the RAB, taking a 2nd and literally start to walk it around the RAB. (Red arrows portray my intended direction). We were going in the region of 15mph, certainly no more than 20mph and it is fair to say although my memory is partial, that I may have slightly straightened the line (Blue large dots). Thats about it. There was nothing special about the circumstances at all. Start to turn in, reach the required angle and balance the car around the bend at a constant speed. Almost at the point I stop turning the wheel to the right, (green cross) the back lets go (small blue dots ). In the following 1 second these were my thought processes:

Oh, bit slippy here...

Shit, really slippy...

Into a rear wheel skid now...

Erm... still turning round.

Shit, this is a big one...

Oh dear....

And there I was facing the car that was behind me on the RAB, who laughed at me, then drove off. It was all very slow, nothing at all was hit and I was aware there was only one car far enough behind me to to worry, so all in all we werent that bothered. But I just couldnt believe it had happened.

I was in complete shock. The main reason being, I just could not fathom how this happened at all. The wife actually laughed as well, much to my amazement, as she usually can't deal with involuntary car movements. She said she felt very safe and how bizarre it was considering how slow we were going. I still to this moment don't get it at all, and made a mental note there and then that on our way back we were visiting that RAB again and inspecting it. FWIW the second my arse went light I turned in the opposite direction, and followed the usual rules.

We returned later and drove round it. It was still wet and my wife said she saw a bit of petrol on the road. I didn't see any however so I am inclined not to think that was the cause. What we did both see and feel however is alot of mud / possible horse excrament on the outer half of the point we span. It was not highly visible but you could see the surface grimed and slightly brown. The point felt slippy as I drive around it but not as slippy as oil / petrol / ice etc, more like surface debris slip.

So I am left with 2 possible reasons that I can think of:

They are:

1) Debris caused the rear wheels to break traction during the turn in / bend and prevented the rear wheels from gaining grip during the correction procedure.

OR

2) Having initiated the rear wheel skid and start to turn in, I was late or sudden on releasing the throttle during correction which "could" have inadvertently contributed the spin by way of lift off oversteer, feeding it etc.

[crr003]

Glad you're both OK!

1. "Diesel" was my first thought, but I read a lot about that on the VX220 forum. Are you FWD or RWD?
2. Do you have ESP? Was it turned off?
3. Not sure you can get lift off oversteer at 15/20 mph?

[waremark]

Great that both of you and the car are all unhurt. Perhaps such an incident is good for all of us, in that it reminds us all not to feel too invulnerable.

I certainly think you can get lift off oversteer at low speeds if it is slippery enough. Presumably you lifted instinctively - many of us would have - but (is this in the fwd VXR) the chances are that made things worse.

You have not mentioned the state of your tyres, especially the rears?

[MikeG]

James, I'm glad that you and the wife were not hurt. My first thought too was diesel, r/b's and bends are the usual places were spillages can occur. My second thought especially after you mentioned mud etc. was the possibility that a farm vehicle may have passed that way. I was out yesterday in similar conditions up on the Yorkshire Wolds and noticed that there was a lot of activity from tractors pulling various trailers and dumping mud all over the carriageway.

Could you have got a layer of mud build up in the tread causing the loss of grip. Sounds as though it must have been extremely slippery for quite a large surface area of the road if you did half a rotation.

[James]

The tyres are great condition, rears almost as good as new. It is a FWD hatch for those asking.

Diesel eh? Would this not be as visible as petrol then?

I thought about what I would see if I parked up for half an hour at the RAB and I am convinced that I would see others go through similar motions. The guy behind me drove on without issue but I guess he must have slowed down to an absolute crawl having seen me spin round.

I think what surprised me most is as has been said, the fact that the car just kept going all the way round. I was pretty quick to get opposite lock on, and when we were at about 45 degrees I would have amost certainly been on full lock, as that angle alone at that speed seems too much. But still the slide continued.

Its likely that farm vehicles would use that route as it is a country road in and out of a village...

[TripleS]

Hiya, James - it sounds like a very sudden, and quite sobering, incident though fortunately harmless in this case. Thoughts:

Does lift off oversteer normally arise from the shift of weight distribution from rear to front, or due to the engine braking effect at the rear wheels of a RWD car if in a low gear? This is just a general question, because I know your car is FWD.

With FWD I would have expected an application of power would have caused the front wheels to produce more lateral slip and take a wider line, thus reducing the tendency to spin the car.

It sounds as if the road surface condition was exceptionally difficult to read and evaluate in this case.

Best wishes all,
Dave.

[ROG]

I saw exactly the same thing happen in exactly the same situation in front of me when I was the first car waiting in a slip road to enter a RBT.

I also saw how it happened.

No problem with the road surface.

It was a FWD car.

As the car got to the point where it intended to move over towards the left so as to line up for the exit - the apex of the RBT from the perspective of the car - it put a little gas on BUT instead of taking the steering off, put a bit more turn to the right on.
This slight increase in speed along with the very slight right steer caused the car back end to come around and it did a 180 - no-one hurt - just a puzzled driver.

[James]

Hmmmm....

That sounds possible if they have applied some power and then increased the turn at the same time. I am pretty sure that I kept my line, but, I was going round a right hander, and I couldnt tell you exactly at what point I put down some drive in sync with what point I started to decrease the severity of the turn.

Very puzzled sounds familiar though!

[TripleS]

Pah - what we all need is a limit handling course.

<runs for cover>

Best wishes all,
Dave.

[7db]

Well done for posting up James, and glad to hear no harm done.

There might have been some magic traction-breaking material on the RAB. I've used that excuse before when I've run out of talent and luck simultaneously. The first step is to blame the right bit of the vehicle-driver system for the spin.

Where did you do your braking?

For terminal oversteer to develop in a FWD, I'd have thought the cause was too much weight on the nose -- either braking to late into the corner or getting scared and lifting.

Overall loss of grip (don't the front wheels hit the diesel first), or overall too much speed, or sudden application of more lock whilst fully balanced would be more likely to make the front wash out, I think.

There was enough grip to oversteer into the inside of the corner so there was enough to get round it (as the following car proved).

Did the car following behind affect your entry speed or positioning into the RAB? Was your mind distracted?

Just few thoughts -- you need to privately figure out what happened if you are to fix this aspect of your driving.

[James]

The braking was well and truly done before I got onto the RAB, I remember as the entrance was slightly curved to the left, and I remember thinking that I wanted to finish breaking before having to turn left and enter the roundabout. Maybe that contributed (left turn followed by sweeping right turn).

Interesting comment about the front wheels not losing grip. I am not sure though that it was a simple as that. I honestly believe the rear wheels went over a surface / something different to the front. When we turned it was as instant, smooth and quick as if you were on a skid pan...

Its possible I lifted slightly mid corner, bit I can't remember that clearly. Not something I would usually do especially in the wet. And if I did velocity was so slow I owuldnt expect a spin. Either that or the rear wheels did hit the muddy bits with more force than the front (as I drifted towards the apex and gently turned then surely the back would start to encounter some extra sidewards force)?

One thing I do know though is that I couldnt re-enact it if I tried

[TripleS]

The braking was well and truly done before I got onto the RAB, I remember as the entrance was slightly curved to the left, and I remember thinking that I wanted to finish breaking before having to turn left and enter the roundabout. Maybe that contributed (left turn followed by sweeping right turn).

Interesting comment about the front wheels not losing grip. I am not sure though that it was a simple as that. I honestly believe the rear wheels went over a surface / something different to the front. When we turned it was as instant, smooth and quick as if you were on a skid pan...

Its possible I lifted slightly mid corner, bit I can't remember that clearly. Not something I would usually do especially in the wet. And if I did velocity was so slow I owuldnt expect a spin. Either that or the rear wheels did hit the muddy bits with more force than the front (as I drifted towards the apex and gently turned then surely the back would start to encounter some extra sidewards force)?

One thing I do know though is that I couldnt re-enact it if I tried

Obviously a not especially well executed Scandinavian flick.

On a serious note though, what are the chances that one of the more stuffed shirt / jobsworth BiB would have criticised you for that sort of driving - even if it was all quite innocent and not boyracerish?

Best wishes all,
Dave.

[James]

Unlikely as we were not going round the RAB any quicker or slower than anyone else. It was a very slow speed, so no chance of being accused as a boy racer...

[crr003]

The tyres are great condition, rears almost as good as new. It is a FWD hatch for those asking.
.
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I was pretty quick to get opposite lock on, and when we were at about 45 degrees I would have amost certainly been on full lock, as that angle alone at that speed seems too much. But still the slide continued.

The Astra VXR?
So it's got ESP. Did you notice if the light was on at all?
Wouldn't trying to correct the skid confuse the poor thing? But I suppose by then the electronics had failed to deal with it.

[Red Herring]

The braking was well and truly done before I got onto the RAB, I remember as the entrance was slightly curved to the left, and I remember thinking that I wanted to finish breaking before having to turn left and enter the roundabout. Maybe that contributed (left turn followed by sweeping right turn).

Interesting comment about the front wheels not losing grip. I am not sure though that it was a simple as that. I honestly believe the rear wheels went over a surface / something different to the front. When we turned it was as instant, smooth and quick as if you were on a skid pan...

Its possible I lifted slightly mid corner, bit I can't remember that clearly. Not something I would usually do especially in the wet. And if I did velocity was so slow I owuldnt expect a spin. Either that or the rear wheels did hit the muddy bits with more force than the front (as I drifted towards the apex and gently turned then surely the back would start to encounter some extra sidewards force)?

One thing I do know though is that I couldnt re-enact it if I tried

Shame you didn't go back and try...I think if I'd been you it would have taken me at least half dozen laps of the roundabout to get bored...

On a serious note the most likely cause of a rear end break away in a FWD car in these circumstances would have been weight transfer from the left/right turn coinciding with the patch of "slippery" road. Unless you were already drifting the vehicle the rear wheels would have passed over the same surface as the fronts, so the question is why did the front stick, and the rear not. The answer may be that at the actual point midway between the weight transfer neither the front or rear wheels are subject to much energy, so as the front passed over that patch of road you weren't actually asking much of it, however as the load transferred (assuming as you said a balanced throttle) the load on the rear nearside was sufficient to cause it to lose traction and break away.