Rear End Stepping Out in Straight Line!

[Jazzer]

Hi, I’m after your thoughts on this.

The rear end of my GTS stepped out on a straight section of the M11 yesterday, prompted by a gentle prod of the throttle in fourth.

The car fishtailed a bit (I thought I was going to hit a lorry!), but came back as I eased off the throttle - PSM really helped.

I’m a pretty experienced rear-wheel driver, but I’m still not quite sure why this happened.

The road was flat, with no discernible camber.

The tyres at the back are down to about 3mm, but they still have decent traction (checked afterwards).

All tyres are wearing evenly, the geometry seems fine.

What do you think?

Edited by Jazzer on Wednesday 15th January 11:33

[SV_WDC]

Not sure but most owners change their tyres at 3mm tread (not the MOT failure of 1.6mm), as 3mm is used by the emergency services.

Other than that lots of things could impact it. Tyre temp, maybe there was oil on the road? Who knows.

But change tyres and see if it happens again?

[PM3]

Same car that had a new engine installed ?

[Grantstown]

One tyre on the white paint causing a difference in traction, or a bit of steering angle if front following a depression is the road surface?

[Snowy999]

Even if dry a bit of spilt diesel/coolant can cause this. Well done on catching it. My GT4 has done this to me several times but usually with standing water.

[Jazzer]

New tyres had already been ordered, they’re being fitted tomorrow.

The back left tyre had more traction at the point of acceleration, that’s clear. Maybe a touch of oil or grease as mentioned, maybe a localised indentation on the road surface - very scary thing for sure.

[Swine Enthusiast]

Jazzer said:

Hi, I’m after your thoughts on this.

The rear end of my GTS stepped out on a straight section of the M11 yesterday, prompted by a gentle prod of the throttle in fourth.

The car fishtailed a bit (I thought I was going to hit a lorry!), but came back as I eased off the throttle - PSM really helped.

I’m a pretty experienced rear-wheel driver, but I’m still not quite sure why this happened.

The road was flat, with no discernible camber.

The tyres at the back are down to about 3mm, but they still have decent traction (checked afterwards).

All tyres are wearing evenly, the geometry seems fine.

What do you think?

Edited by Jazzer on Wednesday 15th January 11:33

Greasy surface/patch of ice etc?

[ChrisW.]

I had this to a limited extend on a 997GT3 when one of my rear tyres was low due to a previously unknown puncture ... maybe that was a rolling radius issue with the LSD ?? But this wasn't so much a stepping out as the car steering itself ?

[Maxym]

Hardly worth a thread on PH.

[Jazzer]

Thanks for the replies, much appreciated.

It was 11 degrees at the time, so ice was not involved.

Tyres were at 35psi all round.

We’ll never know for sure what caused it, but I suspect it was something to do with the surface.

I drove the same road today in damp conditions , gingerly trying third and fourth gear accelerations on largely empty stretches - no drama at all.

[ChrisW.]

Then a diesel spill ?

[Jazzer]

It may well have been something like that, I may just have been unlucky to be accelerating when the rear left wheel hit it. I’m so relieved to have walked away with me and the car unscathed, it could have been a major accident.

[ChrisW.]

Yup, it's easy to be unlucky and maybe a little more challenging to be lucky All's well ...

[modeller]

Had the same happen.
Straight road. Wet. Medium throttle. Massive fish tail.
Dunlop sport Max.

Car now sorned until spring.

[Ed.Neumann]

I take it the same tyres front and rear?

If so, probably something on the road combined with the rears being down to 3mm.

[Chamon_Lee]

unless in the rain with standing water 3mm tread depth will make zero difference. Not sure why people keep mentioning it.

As others have mentioned, fuel or some sort of car liquid is on the road.
Depending on what gen of boxster/caymen you have I would be tempted to have all the suspension checked out as there are reports of the 981 having issues depending on year.

[Jazzer]

It’s the GTS 4.0., Pirelli P Zeros all round (I prefer them to the Michelins).

The traction from the rears was not an issue at 3mm - now running in the new ones!