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kurlykris
Magny-Cours


Joined: 30 Jun 2014
Posts: 2552
Location: Warwickshire


PostPosted: Mon Oct 26, 2015 10:51 pm    Post subject: Re: 2006 Porsche C4S Twitchy/Unstable at high (motorway) spe Reply with quote

Piranha-- wrote:



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
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DerbyJim
Imola


Joined: 25 May 2014
Posts: 753
Location: Surrey


PostPosted: Mon Oct 26, 2015 10:58 pm    Post subject: Reply with quote

+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
 
  
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valdice
Monza


Joined: 14 Jun 2009
Posts: 167



PostPosted: Tue Oct 27, 2015 8:28 pm    Post subject: Reply with quote

top suspension mounts are worn and need replacing when you remove them you will find they are split
 
  
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branko
Newbie


Joined: 13 Mar 2011
Posts: 28



PostPosted: Fri Oct 30, 2015 8:34 pm    Post subject: Reply with quote

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.
 
  
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Jamesyg
Hockenheim


Joined: 13 Aug 2013
Posts: 741



PostPosted: Fri Oct 30, 2015 8:51 pm    Post subject: Reply with quote

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.
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RJKflyer
Montreal


Joined: 30 Aug 2011
Posts: 513



PostPosted: Wed Nov 04, 2015 11:29 am    Post subject: Reply with quote

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.
 
  
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ragpicker
Reims


Joined: 14 Apr 2013
Posts: 4031
Location: North East England


PostPosted: Wed Nov 04, 2015 11:48 am    Post subject: Reply with quote

Sounds very much like a suspension issue to me. As the others have said, get it looked at by someone who knows their onions, not just a guy with a hunter aligner.

My thoughts would be bushes/control arms/top mounts or drop links.
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FRZ 911
Österreich


Joined: 19 Jun 2015
Posts: 897
Location: Northern Ireland

2007 Porsche 997 Carrera 4S

PostPosted: Fri Nov 06, 2015 6:28 pm    Post subject: Reply with quote

Piranha-- wrote:
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
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ragpicker
Reims


Joined: 14 Apr 2013
Posts: 4031
Location: North East England


PostPosted: Fri Nov 06, 2015 6:36 pm    Post subject: Reply with quote

FRZ 911 wrote:
Piranha-- wrote:
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 Question

Surely one might argue that the gun must've been malfunctioning officer and I was only doing 73... Angel
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BOX11STR
Newbie


Joined: 06 Jul 2016
Posts: 5
Location: London


PostPosted: Wed Jul 06, 2016 10:21 am    Post subject: Re: 2006 Porsche C4S Twitchy/Unstable at high (motorway) spe Reply with quote

Piranha-- wrote:
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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Shurv
Kyalami


Joined: 09 Jan 2013
Posts: 1753
Location: Northampton


PostPosted: Wed Jul 06, 2016 10:41 am    Post subject: Reply with quote

Book yourself into Centre Gravity for one of their health checks. They will sort it out very quickly. There are a LOT of adjustments you can make to these cars, and if they are mis adjusted, they can feel downright lethal to drive. If you have any suspension issues, they will be found out. Don't go to an OPC, their "OE settings", can be ok, but the car still be all over the road, these cars need a specialist set up.
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BOX11STR
Newbie


Joined: 06 Jul 2016
Posts: 5
Location: London


PostPosted: Wed Jul 06, 2016 11:05 am    Post subject: Reply with quote

Thanks! I'm booked in for Wednesday... noob question but what's an 'OPC'?
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Phil 997
Le Mans
Le Mans


Joined: 05 Dec 2015
Posts: 15519
Location: Bournemouth,Dorset

2009 Porsche 997 Carrera 4S

PostPosted: Wed Jul 06, 2016 11:08 am    Post subject: Reply with quote

I would be doing as suggested and seeing what centre gravity had to say as what you describing is not how it should be, is it all stock no added spoilers etc as when I had my front aero kit bumper and lip on but not the aero kit rear spoiler as it was getting painted , the car was exactly how you described.
Thumb Grin
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BOX11STR
Newbie


Joined: 06 Jul 2016
Posts: 5
Location: London


PostPosted: Wed Jul 06, 2016 11:18 am    Post subject: Reply with quote

Car is completely stock with no added bits so not sure why this happening. I'm hoping centre gravity can get to the bottom of this and perhaps something is loose or needs adjusting.

Hoping and praying it's not anything serious!!
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T8
General
General


Joined: 29 Jun 2010
Posts: 16085
Location: Kent


PostPosted: Wed Jul 06, 2016 12:09 pm    Post subject: Reply with quote

BOX11STR wrote:
Thanks! I'm booked in for Wednesday... noob question but what's an 'OPC'?


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ps. Welcome to 911uk
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BOX11STR
Newbie


Joined: 06 Jul 2016
Posts: 5
Location: London


PostPosted: Thu Jul 07, 2016 10:28 am    Post subject: Reply with quote

Thanks mate!

Just had the guys over at Jaz Porsche test drive and they've assured me car is spot on.... I guess this must just be me needing to get used to the Physics of the car!

Thanks for the speedy responses!

Cheers,

Sanj
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Pip1968
Suzuka


Joined: 26 Oct 2009
Posts: 1186
Location: Blighty


PostPosted: Fri Jul 08, 2016 4:50 pm    Post subject: Reply with quote

Interesting read I have sent a PM to Piranha to find out the outcome on his problem.

I have to say that having a 996 GT3 the front also feels a little light at speed but put this down to the type of car it is. Mine is set up for fast road/track so that probably exacerbates the feeling.

I think coming from any other car the Porsche is bound to feel very different at speed and more communicative. Not sure how much difference there is with a 997 although obviously there are a few more aids.

Pip
 
  
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Jay Are
Trainee


Joined: 04 Jul 2015
Posts: 88
Location: Kesselchen


PostPosted: Fri Jul 08, 2016 7:40 pm    Post subject: Reply with quote

I had the pleasure of spending a day under the car on the ramp at Centre Gravity recently and they measure everything. Porsches settle, especially at the front which results in toe out and lots of camber. Great for cornering but twitchy as hell if there's even a slight rut to follow in a straight line as the front wheels are effectively hunting for anywhere else to go I.e. Not straight on...

Mine has dropped 18mm on the front so its now GT2 height. It had also destroyed one bump stop. They straightened the wheels and had a play with the camber. Different car... I don't know how good all the various machines are but the guys' in CofG definitely does the trick.

They're good guys too. Very informative.

Recommend a visit
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tobys
Newbie


Joined: 01 Aug 2018
Posts: 1



PostPosted: Thu Aug 02, 2018 12:02 am    Post subject: fixed? Reply with quote

Did you get it sorted Piranha?
have just bought a 997.2 C4S and have very similar issue, apart from mine starts around 70mph.
Yet to check everything suggested here, but if you found a fix it would be great to hear it please.
 
  
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lofi
Barcelona


Joined: 08 Jun 2009
Posts: 1371
Location: Surrey/Kent border

2001 Porsche 996 Turbo

PostPosted: Thu Aug 02, 2018 6:45 am    Post subject: Reply with quote

911s tend to droop at the rear, which changes the angle of the car. Mine was light at the front at motorway speeds. Some shim plates in the rear later and the angle of the car was right and the problem solved.
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