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2006 Porsche C4S Twitchy/Unstable at high (motorway) speeds

Mine was exactly the same. As soon as it went over 100/110 I had to back off as it was scary. The tyres were down to 3 MM. So I put 4 ps2 on and it cured the problem. It'll be tyre or suspension issue IMO.
 
Nicholas Lawrence said:
Love PS2 :drive:

A bargain at Camskill at the moment, I have 2 arriving tomorrow for the front :)

Now, to the OP, don't "buy a splitter", get the problem sorted out. Sounds like bushes, or tyres, or something else from above.....
 
Is the rear spoiler working?
 
resigner said:
Nicholas Lawrence said:
Love PS2 :drive:

A bargain at Camskill at the moment, I have 2 arriving tomorrow for the front :)

Now, to the OP, don't "buy a splitter", get the problem sorted out. Sounds like bushes, or tyres, or something else from above.....

i hope not i not had it long lol brought from a rep dealer too :)
 
Re: 2006 Porsche C4S Twitchy/Unstable at high (motorway) spe

Piranha-- said:
Alignment has be adjusted to Porsche spec with 0 tolerence

Alignment was adjusted by who, are they Porsche specialists ?

Did they set the geometry to the correct values for 997 C4S and not just generic 997 or other ?

Did they check the ride height/suspension sag ?

Did they check the shocks for performance ?

Did they check and adjust tyre pressures ?

Did they check the front weight and compensate with ballast, ie : full tank of fuel before adjustments ?

So many variables and such a vital thing to get right and you have to know what you are doing to get it right.

Take it to Centre Gravity, then it WILL be right, or they will tell you exactly what is wrong :grin:

They pointed out that I had one tyre PS2, OS front that was a different compound to the rest, made the car pull to the left, it could be something as silly as that :frustrated:
 
+1 for Geo / tyres. Mine feels steady as a rock.

Secondly, which motorways are you doing 'nearly 200mph' on them? Let me know so I can avoid!!! :hand:
 
top suspension mounts are worn and need replacing when you remove them you will find they are split
 
Mine was the same (2005 997.1S) following the recent fitting of new tyres. Today JZM did a re-balance of the front two and it has transformed the car! They also noted that the NS wheel has a slight buckle - steering wheel is pretty stable however and will see how she behaves. The type of balancing machine used really does matter.
 
Would be interested in who did the Geo... my tt was like this prior to 9e sorting the geo.

I would say that they all feel a little vague at 100, and then squat again at 110+. Was evident at Millbrook on high speed oval.
 
Longish shot, but when I first had my turbo, and just after having winter wheels/tyres fitted shortly after buying it (so had not pressed on too much) I experienced a very disturbing imprecision/float at 100+.

It was extremely unnerving to drive at speed and I worried that I had bought the wrong car.

I was all set to go get a major alignment, but with 2000 miles on the clock from brand new, seemed an unlikely need on a supposed supercar.

Cutting a longish story short, all returned to perfection after I heard and felt a 'twang' from the front when I pulled into my own drive. Been perfect and rock solid at any speed for 15,000 miles and 2 sets of tyres later.

Can only assume the act of having the car up off of all fours for wheel change at OPC might have unseated a front road spring.

Long shot, but worth a look before getting the 'back off of the set' so to speak.
 
Piranha-- said:
I've been in a 991 Turbo S on the motorway yesterday and the car was rock solid, even at near 200mph. that car was stable enough at those speeds where the owner actually took his hand of the wheel and the car did not budge. (nearly gave me a heart attack, but the car was solid)

I know these cars to be excellent tourers, and that is why i'm not comfortable with the way it behaves, the car just does not seem to be happy on motorways.

The issue is not tram lining as I've tried moving away from the "most used" part of the tarmac, same issue.

Even My daily Audi A1 is a hell of a lot happier at 120mph on the motorway, and I'd expect the C4s to be alot better than Audi's baby car.

Don't suppose this guy was the driver of the 991 by any chance?

http://www.bbc.co.uk/news/uk-england-northamptonshire-34744459
 
FRZ 911 said:
Piranha-- said:
I've been in a 991 Turbo S on the motorway yesterday and the car was rock solid, even at near 200mph. that car was stable enough at those speeds where the owner actually took his hand of the wheel and the car did not budge. (nearly gave me a heart attack, but the car was solid)

I know these cars to be excellent tourers, and that is why i'm not comfortable with the way it behaves, the car just does not seem to be happy on motorways.

The issue is not tram lining as I've tried moving away from the "most used" part of the tarmac, same issue.

Even My daily Audi A1 is a hell of a lot happier at 120mph on the motorway, and I'd expect the C4s to be alot better than Audi's baby car.

Don't suppose this guy was the driver of the 991 by any chance?

http://www.bbc.co.uk/news/uk-england-northamptonshire-34744459

Interesting article. The copper said that 192 was 'way, way more than a speed camera could record'... So at what speed do they stop being accurate/recording?

I have *ahem* friends who regularly approach this type of speed apparently. If they went past a copper and the gun wouldnt track the speed but then slowed down for the plod to catch them up, I wonder what the likely charge would be :?:

Surely one might argue that the gun must've been malfunctioning officer and I was only doing 73... :angel:
 
Re: 2006 Porsche C4S Twitchy/Unstable at high (motorway) spe

Piranha-- said:
Hi,
Have been having an issue with the '06 C4S for a while now, and I cannot seem to get to the bottom of it.

Car handles great on track and curvy roads. Steering is precise, accuracy is great, and steering feels very sharp. The car really inspires confidence in the twisty bits (even bombing through long corners at 100+mph).

Driving on motorways at approx 70 mph is ok, but anything higher that 100mph and the car feels twitchy and the car does not inspire confidence. tried both sport on and off, inc pasm on/off and all combinations, but nothing seems to fix this. It feels like steering inputs are amplified at high speeds making the car nervous.

Tires are porsche spec (N) Michelin Pilot sport
Alignment has be adjusted to Porsche spec with 0 tolerence
Wheel balancing is perfect.
What else shall I look at?

Hi guys - sorry to hijack this post but I'm having exactly the same problems as Piranha. This is my first Boxster, having never driven or owned a Porsche before...

A bit about my car:
Stock 2011 Gen 2 Boxster S 987 (Sport Chrono, no PASM)
19 inch wheels
Full service history at correct intervals
1 owner 44K miles
Just had major service at 43K by Revolution Porsche
Brand new set of N-rated Michelin PS2 all round 300 miles ago with correct balancers
Four Wheel alignment carried out by Jaz Porsche a day after new tyres

Like pirana's car, it feels fantastic on twisty bits however since I've owned the car - it just feels incredibly nervous on motorway north of 70mph. The whole front end feels light (I know that's the way these cars are designed) but it just feels incredibly twitchy, steering overly sensitive and not confidence inspiring at all. There's no play in the steering nor noticeable vibrations either.

Furthermore there seems to be no knocks, squeaks or rattles from the suspension and the spoiler works completely fine - so what can it be??

Absolutely gutted I've spent years saving for my first ever Porsche and I've got all this power under my foot yet I still feel safer doing 90MPH in my mum's peugeot 307 1.6!!

Looking forward to all your thoughts!

Thanks!
 

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