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Piranha--
Newbie


Joined: 26 Oct 2015
Posts: 4



PostPosted: Mon Oct 26, 2015 11:05 am    Post subject: 2006 Porsche C4S Twitchy/Unstable at high (motorway) speeds Reply with quote

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?
 
  
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Robertb
Dijon


Joined: 01 Sep 2003
Posts: 7106
Location: South Oxfordshire

2002 Porsche 996 Carrera 4S

PostPosted: Mon Oct 26, 2015 11:19 am    Post subject: Reply with quote

Sounds odd... they are usually rock steady, at least my 996 4S is.

They are susceptible to tramlining on m-ways over the dips left by lorries etc, but all cars are to an extent.

Maybe the geo could be tailored by someone like Centre Gravity to suit your driving style better rather than the one size fits all Porsche settings.
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Gollom122
Suzuka


Joined: 21 Jul 2010
Posts: 1144
Location: North East England


PostPosted: Mon Oct 26, 2015 11:21 am    Post subject: Reply with quote

I'd be tempted to say 'Go drive another one' These cars are very rear heavy due to the engine being there and not up front. Simple physics means that the faster you go the lighter the front will be, however the effects of down force will reduce this. Assuming you have standard body work it may just be that you are not feeling comfortable with this - hence my suggestion to test your feeling in another car.
Are all your under body covers securely in place?
 
  
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Piranha--
Newbie


Joined: 26 Oct 2015
Posts: 4



PostPosted: Mon Oct 26, 2015 11:29 am    Post subject: Reply with quote

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.
 
  
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T8
General
General


Joined: 29 Jun 2010
Posts: 15634
Location: Kent


PostPosted: Mon Oct 26, 2015 12:57 pm    Post subject: Reply with quote

Does it feel twitch or just a bit 'vague' Question

I say that because my 996C4, and to a lesser extent my 996T, felt a bit disconcerting at around 100-110.

On my first airfield day I braced myself for what might happen after that and was pleased to find that over 110 the car just squatted and pushed on feeling a lot more planted.

Since that day I never gave it another thought. Very Happy
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mavster
Monza


Joined: 11 Aug 2012
Posts: 241
Location: East London/Kent


PostPosted: Mon Oct 26, 2015 2:06 pm    Post subject: Reply with quote

Do you still have all the plastic under trays in place under the car? Does the boot spoiler deploy?

Sounds very strange, I bet it must be annoying being told you are imagining it. wack I hope you get this resolved.
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Piranha--
Newbie


Joined: 26 Oct 2015
Posts: 4



PostPosted: Mon Oct 26, 2015 2:19 pm    Post subject: Reply with quote

T8:
Not Vague, car is definitely twitchy between 100 and the 140-145mph (did not risk going above 145mph).
between 70 and 100mph car is ok, but still not as stable as I would expect. Definitely not imagining it, both my father and I feel the car, yesterday also had a passenger who commented on how twitchy it is. Same guy also said that the car moves about alot on the motorway (when driving in the 991 Behind us) and he also commented how composed the car looks in fast corners. (which is my opinion too)

Mavster:

All plastics underneath are fitted, intact and in perfect condition.
Rear spoiler deploys and works well.
 
  
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M9JOC
Spa-Francorchamps


Joined: 10 Jul 2014
Posts: 373
Location: Aberdeen


PostPosted: Mon Oct 26, 2015 2:52 pm    Post subject: Reply with quote

Piranha-- wrote:
T8:
Not Vague, car is definitely twitchy between 100 and the 140-145mph (did not risk going above 145mph).
between 70 and 100mph car is ok, but still not as stable as I would expect. Definitely not imagining it, both my father and I feel the car, yesterday also had a passenger who commented on how twitchy it is. Same guy also said that the car moves about alot on the motorway (when driving in the 991 Behind us) and he also commented how composed the car looks in fast corners. (which is my opinion too)

Mavster:

All plastics underneath are fitted, intact and in perfect condition.
Rear spoiler deploys and works well.



I was going to say the plastics underneath, One of mine was missing and what a difference once it was replaced.

Is the bit of road your travelling on exposed to high wind or anything.
There is an area of my journey i do each day that if its really windy it will shove the car about.

Bag of sand in the front compartment to see it the weight steadies her.
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20" HRE Alloys on Continental tyres, 9E Stage 2 inc IPD,TB & chrome Y-Pipe, Europipe+100CEL, -20mm H&R springs. Gen 2 front & Rear bumpers, Chrono, Adaptive Sports Seats, Full Porsche Aerokit
 
  
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Piranha--
Newbie


Joined: 26 Oct 2015
Posts: 4



PostPosted: Mon Oct 26, 2015 2:53 pm    Post subject: Reply with quote

Last tested on a 380 mile trip, many different road conditions, same issue though Sad
 
  
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stressballsteve
Monza


Joined: 19 Sep 2014
Posts: 164



PostPosted: Mon Oct 26, 2015 3:46 pm    Post subject: Reply with quote

I'd look at the following:
tyre pressures
wheel nut tightness
wheel bearing possibly on its way out?

Have all the bolts that hold the suspension to the car been checked?

Hope you find the answer...
 
  
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Waz
Estoril


Joined: 14 May 2011
Posts: 3504
Location: Sutton coldfield


PostPosted: Mon Oct 26, 2015 5:05 pm    Post subject: Reply with quote

What you describe is exactly how mine felt, to the point I was gonna sell it,
Took it to centre gravity, top bushes where kaput, I also had it set up to fast road,
All I will say is the difference is night and day, that was 4 years ago and I still have it, Thumb
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nicholas lawrence
Barcelona


Joined: 10 Apr 2014
Posts: 1319
Location: United Kingdom


PostPosted: Mon Oct 26, 2015 5:35 pm    Post subject: Reply with quote

Buy a front splitter.
 
  
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knite
Newbie


Joined: 12 Oct 2015
Posts: 41



PostPosted: Mon Oct 26, 2015 6:00 pm    Post subject: Reply with quote

Nicholas Lawrence wrote:
Buy a front splitter.


I know what you mean and the guys are right, I was thinking of buying a front spitter as it does feel very light at the front end when under high speed. I know it certainly makes me a scepticle about driving fast.
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nicholas lawrence
Barcelona


Joined: 10 Apr 2014
Posts: 1319
Location: United Kingdom


PostPosted: Mon Oct 26, 2015 6:01 pm    Post subject: Reply with quote

Drive mine it won't feel weird at speed.

Based in Norfolk
 
  
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lofi
Barcelona


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

2001 Porsche 996 Turbo

PostPosted: Mon Oct 26, 2015 6:08 pm    Post subject: Reply with quote

I'd get the ride heights checked. My 996T was a bit like this. It has slightly sat on its rear suspension (not by much). When returned to the right heights and particularly the right rake front to rear it was completely cured.
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------------------------------------
996 turbo tip
ex 944 2.5 manual
ex 964 C4 manual
 
  
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Alfaian
Imola


Joined: 12 Mar 2014
Posts: 824
Location: S.wales


PostPosted: Mon Oct 26, 2015 7:43 pm    Post subject: Reply with quote

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.
 
  
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nicholas lawrence
Barcelona


Joined: 10 Apr 2014
Posts: 1319
Location: United Kingdom


PostPosted: Mon Oct 26, 2015 7:56 pm    Post subject: Reply with quote

Love PS2 Drive
 
  
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resigner
Suzuka


Joined: 19 Dec 2013
Posts: 1216



PostPosted: Mon Oct 26, 2015 9:09 pm    Post subject: Reply with quote

Nicholas Lawrence wrote:
Love PS2 Drive


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

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


Joined: 20 Oct 2013
Posts: 956
Location: Leicester


PostPosted: Mon Oct 26, 2015 9:20 pm    Post subject: Reply with quote

Is the rear spoiler working?
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knite
Newbie


Joined: 12 Oct 2015
Posts: 41



PostPosted: Mon Oct 26, 2015 9:26 pm    Post subject: Reply with quote

resigner wrote:
Nicholas Lawrence wrote:
Love PS2 Drive


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

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 Smile
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