911 rear end slide out. what speed ??
 

Hi Guys
new owner of my 84 Cab
Just got a new set of Mich AS4 on 205 55 r16-225 50 r16
I am just wondering at what general speeds should i watch my rear to go?
i'm sure the car should hold down at regular posted highway speeds?
But what about those tasty little on/off ramps with diminishing radii etc?
i did look it up and do find a lot of info but i'm not racing. i might push it in corners about 10-20 kph over if it's empty or i can see the other side but i almost feel like i can corner in my 06 Rubicon faster without freaking out!! lol
advice and tips?

Considering we're discussing a 40 year old car that has likely experienced suspension and alignment changes since new, pinpointing the exact speed the car will break loose would be very difficult. Taking into account weather, road conditions, driver inputs, etc... this would be tough to nail down.

My advice: find a large, empty parking lot and slide the car around. You could attend a formal autocross, but 15 minutes in a parking lot will tell you what you want to know.

Do you warm the tires before hooning? Getting know the car will help you modulate the throttle.

There’s no way to answer that question with speed alone. You can spin a 911 at 20 mph and also drive it perfectly through a corner at 120+.
Take it to an autocross! That is the best way to play with the limits in a safe environment (and to learn how to drive it while you’re at it.) .

The reputation for a 911 to be more tail happy is a false one . Any car will loose the front or rear end as the limit for traction is exceeded .
It has to do with the way the car has been aligned , ride height ,tires , sway bars ,tire pressure .
A front drive honda or any front drive car can swap ends in a blink .
Driver input is also at the top of the list , the car only does what the driver asks for .
I think you should sign up for auto cross , Porsche driving DE events , or true driving classes .

My guess is you do not have any real driving experience at the limit of any car .
Go to school so you do not crash your car

Ian
why do i have this opinion ? look at my profile .

https://www.google.com/search?q=ian+rs+911+clone&oq=ian+rs+911+clone&gs_l crp=EgZjaHJvbWUyBggAEEUYOTIGCAEQRRg90gEIODA0MGowaj eoAgCwAgA&sourceid=chrome&ie=UTF-8#fpstate=ive&vld=cid:38ba29fd,vid:MPVV04V7Zcc,st: 0

MrScratch -- be sure to read up on the physics of our rear engined cars - i.e. how weight-shift from braking/acceleration can have a unique effect. The easiest way to get into trouble is to enter a turn too fast, suffer understeer and then hit the brakes to slow down. Doing this will transfer grip away from the rear tires to the front and cause the rear end to swing around like a pendulum. "Slow in, fast out" (drive into a turn slower than you think you could and accelerate through the turn) is a good mantra to follow. Also, strongly suggest that you get some autocross experience and/or a PCA driver's ed/track day program or 3 under your belt to help fully understand the unique handling traits of our 911s.

Also, what size tires did you end up going with? you mention 215 width tires up front? 205/55-16 is the stock width for front tires, if you have 215s up front keep an eye on their sidewalls for evidence of scuffing on the inner front fender lips and roll your inner front fender lips as soon as you see any evidence of scuffing to avoid damage to both your new tires and the fender lips/paint

Finally, keep in mind that new tires generally require 5-600 miles of use before the greasy coating applied during manufacture to allow the tires to release from their mold wears off. Suspect you'll find your tires' performance to improve significantly as they break in.

It doesn't sound like you're driving aggressively enough to be worried about this sort of thing at all. If you're pushing it more in a Rubicon than a 911 you're just fine.

If you want to find out, do a driving course and get an instructor to whip you around on track at speed.

thanks! hard to find one here with no cars in it or speed bumps and parking blocks.
i'm also talking about regular driving. like highway speeds. not so much track.

Define "tail happy".

Let's be real here. Lift throttle oversteer is a real thing with rear engine and mid engine performance cars setup to handle neutrally. It is more prevalent with rear engine cars. The 911 is well know to be prone to lift throttle overseer.

So, if "more tail happy" includes lift throttle overseer, then the "more tail happy" reputation of a 911 is not a false one...

Hi thanks!
yes the care has 205 up front and 225 in back, my mistake.
that is also what is on the tire size sticker on the car.. on 16" rims.
my question was more along highway driving.
here in BC, we have a few winding highways with anywhere from 80-120kph limits.
i just was thinking that i should not have to be breaking into corners at speed limit speeds on a highway in a Porsche? lol
i don't speed really and not interested in smashing my new car up or getting it impounded by the boys for doing 40 over..
just looking for reassurance that my high performance german sports car can take corners at highway speeds lol

Ah ha. Now is the time to go to a race track.

I don't mean driving like you want to be the next Michael Schumacher, but just going a bit faster than you would on the street. A great way to learn just what a great handling car you actually have and what % of maximum you are driving at.

Around here we have whats called "Track Day" and every and anyone can drive on the track for 15 minutes for $25. Lots of boy racers but they are very respectful of others cars. Then we have "Practice Day". Practice day is for real drivers LOL to practice a week before a serious race. Still only about $75 but they didn't really want us amateurs on the track so we raced around when the big dogs weren't busy.

Uhhhh yeah you're fine. Unless you're approaching .8g or above and playing with the throttle while going down the highway you're not going to be having any problems.

No advice on the internet can replace seat time in the car. Go drive your car and learn it inside and out before you explore the limits. Take a high performance driving class with a local track group. Practice. Then enjoy the fell out of your car.

"How long is a piece of string?"

But seriously, I agree with the above suggestions to find out for yourself in a safe environment.

Get yourself in a nice big parking lot and have at it. Or if your area runs auto-x days, sign up and have a blast. An experienced driver in the passenger seat will push you if need be. Then at the EOD, have one of those experienced drivers, drive your car and you will be amazed at what your car can do.

There's no exact answer for this. Conditions determine limits and as those are always in flux, you can't make a blanket statement for such a thing.

Sign up for some autox and find the limits if your car in various conditions. Seat time is the best way to learn limits. Don't find them on the street.

will sign up but i have a cab. i think i have to have a roll bar?
that's a summer thing.
got a local
shop that can build one apparently.

Look at it this way - if these cars couldn't handle normal roads, at normal (or even slightly above normal) speeds - this forum would be more of a "hey, remember that cool 911 from back in the day" - all of them would have been crashed already :)

If you are a "follow the posted speed limit" driver, you are fine ... 67 Beetle can handle that just fine ... your 911 should have no problem.

"Scott you ignorant slut "
It would seem you have never driven a front wheel drive Acura Integra , Honda Civic ,VW Golf in race car trim or proper street trim. The difference between FWD and RWD
is not what will happen, it is is how do you recover .

It is Physics that dictate the oversteer , understeer, action of any and all cars .

The rear engine car may tend to have a stronger secondary momentum habit .

It would seem that you have forgotten, for general purposes ,weight equals traction


Ian

The last 911 I saw "off road" was a late model water cooled variant next to one of those ramps, a couple years back.

Yeah, good tires but ...

You are seriously dating yourself with a line like that :)

Funny, I didn't mention RWD or FWD or AWD.

I have forgotten nothing about physics. First, let's be clear that mass and weight are different things and that load is what you probably mean when you say weight when discussing vehicle dynamics. Mass never moves around but the load generated by the mass does.

Load does not always equal traction because load is not just a vertical component of vehicle dynamics while moving . If load did equal traction, stiffening an anti-roll bar at the front of car would mean that understeer would be reduced, not increased.

Regardless of what you wrote, the mass distribution of a vehicle certainly affects what will happen and not just how you handle what happens.

Again, the "more tail happy" reputation of a 911 is not a false one...

My advice is to sign up for a Porsche Performance Driving School. This will illustrate a number of highly relevant vehicles dynamics you need to know, feel, and understand in order to drive your car with a degree of competence. This is very much unlike driving your sedan down to the grocery store, or to the office.

When will the back end come around? When you exceeded the limits of adhesion. When is that? That you have to find out by driving over the limit in a controlled setting - a random parking lot is not that setting.

I guess what i really need is to know what to do to not have that happen. however, as long as it doesn't happen in a normal highway/ street setting i'm happy!

And that is why the first thing I did after collecting my 911 and joining PCA was signing up for the PDS class. There they teach you how to drive the car with your feet!; your hands merely assist.

Once you know how to do that you will have the feel of the car, but also understand how to listen to what the tires are telling you. That said, this car will come around on you with almost no warning when you put the car outside its performance envelope. That is why if you need to find that limit, the PDS and follow up autocross is the place to find it.

Depends on your region, but for auto-x, usually no bar is needed. Some driving events, track wise, yes, but most of those you don't need as well. You just need to pass, tech.

To answer your question. It won't step out.
The tires provide the traction, not the car.
If you go beyond the traction of the tires it will understeer.
If you let off it will oversteer.

135 kph. ...... more or less.
SmileWavy

https://www.amazon.com/Porsche-High-Performance-Driving-Handbook-Elford/dp/0760327548/ref=asc_df_0760327548?mcid=f9a2697f782f3512b33045d 057e572c1&hvocijid=1862496347064966633-0760327548-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=721245378154&hvpos=&hvnetw= g&hvrand=1862496347064966633&hvpone=&hvptwo=&hvqmt =&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9030895&hvt argid=pla-2281435177618&psc=1#immersive-view_1737141920547

This would be worth a read.

My $0.02.

If you've never driven a rear-wheel drive car in low-traction conditions, then go to a skid pan and practice making it slide - and counter-steering. Even if you have, take the 911 - it doesn't behave exactly the same as other cars, and you should get a feel for how it behaves, and for how to gauge weight transfer.

It's all about the weight-distribution; the only way I could get the rear to break loose was to approach turn-in at high-RPM/WOT, front suspension light, let the throttle slap entirely shut and turn-in/resume WOT as soon as weight transferred to the front (and unloaded the rear). Then counter-steer through the slide.

I found it very illuminating just how difficult it was to induce the rear to break loose with good tires, even in the wet with abrupt/violent changes of direction (hint: remove anything/everything loose in the cabin first). Took a lot more deliberate effort than I would ever have thought before I tried. Repeatedly.

If you don't lift off the throttle (or brake) whilst turning, you're probably quite unlikely to ever provoke this in normal driving at appropriate speeds... As a rule of thumb, aim to always be, at turn-in, driving the speed you intend to drive through the corner at. If you miscalculate, stick to it - the car is capable, and probably has far more in reserve than you think - driven correctly. Even if it feels pucker-inducing half-way round, unloading the rear is never the right thing to do...

Somewhat counter-intuitively, adding more throttle makes the rear squat, providing more grip at the rear (also unloads the front, reducing traction there). Kind of an advanced technique best avoided mid-corner... Develop your feel for the weight distribution first.

Also of interest may be the "Porsche High-Performance Driving Handbook" by "Quick Vic" Elford, who knew a thing or two about driving Porsches fast - including in rallies on loose surfaces, where much of his early career wins were.

He does talk about how you need to be careful to detect/be ready to control rear-end momentum on a rear-engined car, as pendulum effect will tend to make it get away from you faster than front or mid-engined cars would. As well as explaining concepts like how you can't use more than 100% of the traction available to the tires, and you need to choose whether to use that for braking, steering or transferring power.

I'll bet Ian texts in complete sentences with punctuation too...

MrScratch: I'll reinforce the advice to get some performance driving instruction. I'll suggest to start with Autocross at your local PCA chapter.

thanks! just ordered it

thanks
i'll do that as spring comes around

I joined PCA in around 1987. I started driving on track in 1988. Lime Rock Park with PCA. No karting or AX or anything related prior.

Transormative experience.

Arrived in Norcal in 1991. Lots of AX in the 90's, and time trialing, and racing until about 2017.

And instructing.

One of my old friends in the high-level AX space is Steve Lau:

https://www.youtube.com/watch?v=7pDeslmjf7g

https://www.youtube.com/watch?v=fJNm-U7wtQw

He and his wife are PCA and National Champs.

I was one of Steve's first AX instructors.

One of the first "reference materials" I reviewed for performance/competitive driving was the Skip Barber video "Going Faster." It was filmed at LRP in '86 or so, and I have been watching and recommending it since then.

In '94 I attended a PCA two-day AX school, and the leader of that had written a book called "Secrets of Solo Racing." We all got a copy.

Both reference materials are highly recommended.

My best student ever climbed the curve quickly, starting in a 944, then a 951 that was extensively developed over 5 year period. At the end it had about 360 bhp, a racing suspension and brakes, and big sticky dots. But it was still a 2900 pound street car.

Then we bought our current car, a 1950 pound 911 in 2001. Really a race car with lots of power and big sticky full slicks. And a 915. Very different from a heavy, high powered, front-engined 951.

She drove it in about 2-3 track days in Winter 2001-2002. First 2002 PCA time trial she started getting up on the tires in February 2002.

Second one, she got send overall in time trial at Laguna Seca in March '02.

Third one, she got TTOD at Buttonwillow. She beat the chief instructor. He had 2x the power in his very potent 911. He wrote "Secrets of Solo Racing."

As far as I know, only woman to get TTOD at a PCA TT.

Learned the basics, and focused on the craft.

For many, AX is a good place to start. A few events, then an AX school.

I bit less expensive in time and money than going straight to track events. And perhaps more readily accessible.

On a "cold" winter's day, 25 mph ...

http://forums.pelicanparts.com/uploa...1737251167.jpg


... in the shade.

I’m going to be a bit of an outlier here and not suggest you take classes (although an excellent idea) and say that as long as you keep your speeds reasonable, have tires that aren’t too old and not brake hard in corners, you won’t come anywhere near the limit.

I only had one real close call in my 35 years of 911 ownership and that was in the rain on ten year old tires turning onto an off ramp at too high of a speed; I didn’t loose control, but it was a wake up call and I got new tires the following week.

Only one answer to that question: "just try it!"

Thats the problem qith the internet advice to the Q you are asking. The advice is good - but you can't get a feel for it over the internet. Only your backside in the seat can feel it.
So you are going to forever be a nervous driver if you do not KNOW how far from the limit you are. You could be well inside but muck up a corner a bit and get very anxious and wonder how close you were.
Thats not really the way to enjoy a car that was meant to be driven.
Like most have said - experience the limit in a controlled environment, your confidence and understanding of the car, and an appreciation for what it is, will grow enormously. The internet can't do that for you.
Alan

Yeah, the internet is full of advice and this forum is no exception but keep in mind the common trait is that everyone here is a "survivor" of sorts at their own level of the hobby.

You won't hear from those who didn't ... and I don't mean in a literal sense ... here.