911 rear end slide out. what speed ??

[Bill Douglas]

Trackday experience has saved my bacon.

I was coming home from just having had four new tires fitted to the 911 and wasn't going fast. But there was a very slow bus going downhill through a S bends section of road. I decided to pass and WHOO I was going completely sideways past the bus and still in the S bends. I said to myself remember Manfeild Raceway and I gave it just the right amount of gas to not go backwards into a powerpole and to make the rest of the S bend. I suspect the tire company had coated the tires with something like silicon to make them shiny and pretty.

[spuggy]

Originally Posted by Bill Douglas

I suspect the tire company had coated the tires with something like silicon to make them shiny and pretty.

Takes a dozen or so miles to scrub off the mould release coating on new tires...

I was driving to the track first thing with a brand-new set of Direzzas once, in light rain - and had to brake hard/abruptly on the freeway because everything stopped. Fully expected a bad outcome - but I'd apparently got enough miles on them by then, they behaved like champs...

[Alan L]

That release coating is even worse in the wet. Like a bar of soap. There really probably should be a warning over that. Someone goes out with a flash set of new tyres thinking - whoohoo, I've got super grip now.......
Thats what people mean when they say ' scrubbing the tyres in". Scuffing them up to get rid of that surface coating.
Alan

[Alan L]

That release coating is even worse in the wet. Like a bar of soap. There really probably should be a warning over that. Someone goes out with a flash set of new tyres thinking - whoohoo, I've got super grip now.......
Thats what people mean when they say ' scrubbing the tyres in". Scuffing them up to get rid of that surface coating.
Alan

[pmax]

I suspect going sideways would scrub those tires in ... in a hurry ... helping regain traction.

[A930Rocket]

^^^ I scrubbed my tires in at 100 mph.

https://www.youtube.com/watch?v=gLPH7tFUVwQ

https://www.youtube.com/watch?v=VchkuH6X5FI

[Bill Douglas]

Hehe, that's quite fast for a bit of off-roading

[pmax]

and to top it off, Majel Barrett intones .. 9.36 seconds ...

[unclebilly]

So many variables…

If you want it to slide out, put in heavier torsion bars and a stiff antisway bar.

In our chump 911 we ran no rear sway bar to keep it as driver friendly as possible. I did get it to rotate (spin) at Spokane in a race but it was very predictable up to that point. Far better than my other 911 track car with 29mm rear torsion bars and a stiff rear sway bar.

[WP0ZZZ]

Originally Posted by MrScratch

I am just wondering at what general speeds should i watch my rear to go?

From a vehicle dynamics standpoint, framing it in terms of speed is not quite right.

As a first approximation, you could ask the question: "at what lateral acceleration should I watch my rear to go?"

There are plenty of second-order effects though. Some of which have already been mentioned in this thread.

[Alan L]

Originally Posted by A930Rocket

^^^ I scrubbed my tires in at 100 mph.

https://www.youtube.com/watch?v=gLPH7tFUVwQ

https://www.youtube.com/watch?v=VchkuH6X5FI

Super nice throttle control - thru the corners - nice to watch. Poetry in motion.
Those flat high speed long corners are a challenge.
Alan

[GH85Carrera]

As all have said, there is no speed it will just suddenly oversteer. The summer of 2024 I was at Talladega Super Speedway going 125, AC pumping cold air, and my wife in the passenger seat, just cruising.

You can have oversteer easily in first gear in a tight turn. Tire pressures and suspension setup make huge differences, but the lose nut behind the steering wheel is the biggest determination of it.

[Bill Douglas]

I've found a good place to practice 911 handling is on a gravel road. Obviously with no one coming the other way LOL

Understeer happens easily , and oversteer happens VERY easily, without going fast. It's like taking your puppy to the dog beach - a lot of learning about what point gets you into trouble and how to get out of trouble.

[pmax]

Originally Posted by A930Rocket

^^^ I scrubbed my tires in at 100 mph.

https://www.youtube.com/watch?v=gLPH7tFUVwQ

https://www.youtube.com/watch?v=VchkuH6X5FI

Nice save !

Looks like an offroad excursion well traveled by others less skilled.

[A930Rocket]

Originally Posted by pmax

Nice save !

Looks like an offroad excursion well traveled by others less skilled.

I certainly left my mark. In addition to rubber, there’s oil, from when an oil cooler line popped. Needless to say it was an exciting ride, just missing the wall at pit out.

This was at Roebling Road last spring.

When you see the windshield wipers, that’s me turning off the engine, as I didn’t know if I blew the motor up, fire, etc.

[pmax]

^^^Yeah .... skid marks ... I won't ask further
That's a nice track with the wide expanse of flat grassland next to the tarmac.

I actually meant the second incident by my previous comment which you did save.

[A930Rocket]

Ah. That save was right after the kink on the back straight at Carolina Motorsports Park last fall. It happened so fast, and there was a 90° left-hand turn right after it. Didn’t have time to think about what could’ve happened. That’s why I will always track the BMW versus the 911.

[GH85Carrera]

When I did Robeling Road in a HPDE, they did not know me at all as I am from Oklahoma, and they assigned me an instructor for the first run. I ended up with the head instructor. Coming onto the front straight, I overcooked the turn and had my tail hung out as we slid out to two wheels in the grass. I calmly and instantly corrected the situation as I knew the grass was not good traction. I got it straight and continued on for several more laps. The instructor said you get bumped to the next level up, as you did great on the grass excursion. He added stay off the grass with a grin.

Years of autocross and an many HPDE as taught me how to keep an analog car on track.

My daily driver is a 1986 El Camino with a limited slip rear end. Driving in the rain can be tricky. Leaving a stop sign or red light and making a right turn, I know to give it very little throttle. I can pop the rear end out and take the corner sideways easily as I say weeee. My wife punches me in the arm when I do that

[MrScratch]

Originally Posted by A930Rocket

I certainly left my mark. In addition to rubber, there’s oil, from when an oil cooler line popped. Needless to say it was an exciting ride, just missing the wall at pit out.

This was at Roebling Road last spring.

When you see the windshield wipers, that’s me turning off the engine, as I didn’t know if I blew the motor up, fire, etc.

so what happened? looks like you came out of that corner but went straight into the grass?
did the rear end catch and push you off your line?
looks like you made that corner before that happened?

[A930Rocket]

Originally Posted by MrScratch

so what happened? looks like you came out of that corner but went straight into the grass?
did the rear end catch and push you off your line?
looks like you made that corner before that happened?

I came out of turn nine and was about 1/3 of the way down the front straight, when I saw smoke coming from the dash and when I looked in the review mirror, there was a ton of smoke behind me. The end of the concrete wall is pit out and about halfway down the track.

After getting it towed back to my staging area, we loaded it onto my trailer, and I brought it home. Long story short, one of the oil lines from the oil filter housing to oil cooler popped off the fitting.

I was using Aeroquip push on connectors and Aeroquip hose. It was rated for the oil pressure and temperature, but I suppose being hot, it’s softened enough that the oil pressure pushed it off. I cleaned everything up and installed two.Otiker clamps on each end of the oil lines. No problem so far.