Wet handling
 

Got myself a little surprise tonight - the backend stepped out a frightening amount.

As we know it's been raining quite a lot recently - in fact i dont think i've driven the car for more than 40 of 600 miles without needing the wipers! And I've tried a few times now on wide empty roundabouts to provoke the backend with a powerslide, but all it's given is a little slip and then the DSC has caught it.

But tonight i dont know what happened. Just driving home, not too fast, came off a roundabout, applied some power as i straightened up and whoosh :eek: - bye bye back end - just like my old TVR. I instinctively dialled in a quick correction to catch it - just as well as a pair of headlights flashed past in the opposite direction :D

Odd I thought - i checked that the DCS was not switched off and then i even stopped and tried a burnout start. But i couldnt provoke any slippage from the wheels.

I dont think it's the dreaded wet handling that Clarkson was on about - he was going more down the twitchy line.

As I said plently of rain around recently - anyone else had 'fun'?

Nothing as exciting as bugbear's tale. I was on a T junction turning right. The road was a little bit wet, but not soaking. It had stopped raining for a while.

Without pushing the engine at all (only 200 miles so far), I managed to spin one of the rear wheels as I drove off, turning right. Traction was on, and I could not repeat it again when I tried to.

Now I thought that with traction control:
1) I am not supposed to spin the wheels even if I want to
2) I really was not pushing it when the wheel span. With or without TC, that wheel (or wheels, I guess) should not have spun.

Oh, and it stopped spinning when I pressed the clutch again. TC did not stop the spinning, Surely my reaction is not faster than TC.

If one rear wheel is lifting slightly due to suspension loading (adverse camber, sharp steering input, lots of lock) then this makes it easy for the unloaded wheel to spin and tends to drive the rear end out until the suspension recovers and both wheels are carrying a more equal load again (when you could get some snap back oversteer if you turned into the slide and didn't start to straighten up soon enough)
The differential will help things when the imbalance in load is quite small. The DSC and TC will also presumably help.

However, taken to an extreme (one wheel off the ground) then whatever the power train does, whilst there is power to the driven wheel, the car won't go straight and the back will step out.
Now imagine 140% left rear traction and 60% right rear due to suspension loading. The tendancy to step out is there. The physics and gizmos are going to fight it out.

From experience on my S2000 which has no DSC or TC, but does have a rear differential, what you can get away with varies by some margin and the timing of the throttle is key. I've had major back end out (followed by snap back) moments, at low speeds with moderate but early (unprovoked) throttle in the cold/wet when coupled with off camber roundabouts, yet can take other bends in the wet with aggressive but well timed throttle application at speed.

Sometimes I feel I've applied the same inputs to the same corner but got a different result. These are the ones to worry about.

Why not do a track day and find the limits / traits of the chassis/electronics safely? I learnt so much on my first track day that proved invaluable on the road.

Each car has its own unique set of vices. It is nice to discover them and live to tell the story, but important to discover the reasons why....
The above is my theory based on my stiffly sprung S2000 which in the warm and dry has a very planted rear end but in the wet ...respect and understanding are required.

had you thought about derv on the road?

This is one of the biggest killers for motorcyclists these days although I am not one I did see a complete programme recently on this.

I have fallen victim to derv on the road - not nice and boy does it make you reach for the immodium! I have also had a petrol tank leak a spot of petrol onto a rear tyre in a ford fiesta 1.4 ghia on a mini roundabout at 10 mph and I did a 720- very scary watching the bollards pass you by again and again.

So I reckon this aint due to tyres or driver its the roads mate amd the crap that lies on them or builds up on them i nthe heat.

specman - derv is mainly what i'll put this down to - for the moment. i know that cars, trucks etc if overfull have a tendancy is spill just coming off a roundabout.

paul - the wheel i could feel and hear spinning was the loaded wheel which is why - i guess - it stepped out so suddenly.

for the moment i'll put it down to odd conditions and i do agree finding the limits of the car safely is very helpful for situations like this.

The TC/DSC deliberately allows some slip/oversteer before it cuts in. The rationale behind this is that you can still have some fun and drive it like a sports car while leaving the electronic gadgetry on as a safety net, unlike in many other cars where the systems are so intrusive that you always switch them off if you want to have some fun.

I think Mazda have got the right idea with this, but perhaps it is not the ideal compromise in bad weather, where you're not out to have fun and you just arrive at your destination with as little drama as possible.

Yep - this is supposed to be a sports car, and not a shopping/school run car. As such some tail happy moments before DSC cuts in should be expected.

It'd be much critisized if the DSC cut in straight away allowing no fun, causing people to ALWAYS switch it off and ending up backwards through a hedge or worse.

chris and rob - i agree - the dsc is supposed to allow some slip for some fun. however the times i've tried to have fun with dsc on it has slipped a little - good. but when i wasn't trying to have fun it didnt cut in at all - i had to correct it. it's the inconsistency which could prove dangerous - but this time i'll put it down to odd conditions!

rear wheel drive cars - need I say more.

Oh Im love wert weather rear-wheel drive fun.

Switched the DSC off and blipped the throttle dropping the clutch at 5000 yesterday from a quiet junction and snaked all the way up the road.

Roll on Prodrive trackday!

i was all ready to write off my slip described above as one-off. but just yesterday, independently, me and the other half both reported nasty (ie unexpected) snaking with the DSC ON.

Sorry, dont you mean lovely tail out fun, without interferance from nannying electronics unless you are in serious danger of swapping ends?

If you've come from a front wheel drive car, it will take some time to get used to the differences. Instead of turning in early and using power understear to srub round the corner, you turn in later and apply power on the way out. Get ready to catch the oversteer with a bit of opposite lock - dont get frightened and take your foot of the gas, or worse brake, as then things will get nasty.

Cheers
---Dave

thanks for the advice druck but i've owned rear wheel driver cars for 15 years - including 9 years with a tvr. my point of concern is that the electronics, on mine at least, are not consistant.

I'd 2nd that.

Intervene when I think they shouldnt, give me more leeway at times when I think they should have cut in.

Sounds like there's a problem with the DTR. (That'd be the Driver Thought Recognition)

DTR - like it!

DSC.
Just read this in a magazine tonight, maybe someone can verify if its true or not.
Pressing the DSC button puts the RX8 into 'assist mode'
Holding the DSC button for 4 seconds completely switches off any form of TC etc.....until re-ignition.

Might this explain why some slip is encountered, when people think that their DSC is fully on, but in fact it is in assit mode?

What I mean is, although there is one button, there is infact three modes of DSC. Full, Assist and Off !

gjwinn - no - the button isnt easy to press, you KNOW when you've pressed it.

I've switched mine into assist mode two or threee times in car parks ,never yet on a real road.

It also lights a light saying "DSC off" on the dashboard in assist mode - and lights both the "DSC off" light and the traction control light (car with skid marks) if you switch completly off.

You cant do it by accident or not notice.

DSC fully ON gives you some leeway with skids and wheelspin, though how much that is seems to vary somewhat at times.

I have some more information.

The other (cold) night I found a deserted country road, stopped and triued a few starts ujnder various circumstances.

DSC off, fast start - backed off quickly, as the tyres span and i went no where.

DSC on, slow start (under 3K rpm) - no problem, pulled away smoothly
DSC on, medium start (3-5K rpm) - DSC lit up and I could feel the retardation as the electronics did their work.

Now the interesting one:
DSC on, fast start (5K+ rpm) - the wheels span just as if the DSC was off!!!!

Questions remaining:
I dont know whether this is simply a factor of the revs or whether the fact that the clutch was biting but not fully out had any impact on the ability of the electronics to decide whether to cut in?

Or maybe the japs have been extra clever and said we'll allow some wheelspin for fun and if anyone is stupid enough to drop the clutch at 5K+ they must be out for fun!!