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DarthFaker
Trainee


Joined: 13 Jun 2019
Posts: 93
Location: 1999 Carrera 4 Aerokit


PostPosted: Sat Jan 11, 2020 4:20 pm    Post subject: 996 C4 - Dialing out some understeer. Reply with quote

Hi guys,

I have a 1999 Carrera 4, 3.4L with Aerokit and M030 Suspension.

Overall it handles great, I'm extremely happy with the ride stiffness, it's a road car not a track weapon so I'm not really looking to stiffen the car up loads by fitting Coilovers the M030 is plenty stiff enough for my uses.

I want to shift the handling balance away from understeer and make the car a bit more neutral.

Any suggestions? I was thinking a set of H&R adjustable Sway Bars and using those to play with the handling balance of the car.

How about more front camber using adjustable front control arms?

I'm looking for more steering in off power and on power situations.
 
  
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NedHan79
Hockenheim


Joined: 08 Nov 2018
Posts: 713



PostPosted: Sat Jan 11, 2020 5:01 pm    Post subject: Reply with quote

Hi. My car is a 98 c2 with aero and m030. Ive did a few things to work on the turn in. You don’t need to spend a fortune on parts. I modified my rear arb to make it adjustable. They’re hollow so you can easily flatten the end, drill new holes and go from there. Obviously you need to measure from the bend to ensure the lengths are the same on both sides.
You can also go for arb polybushes. They’ll help tighten it up a little. Small tip though. Remove the old bushes and measure the bar before ordering new ones as the bar wears and the size changes.

After a few small jobs you can get a proper geometry set up. Centre of gravity get a first class reputation for this but I can’t recommend them as I’m in Northern Ireland and have never been but they can’t seem to do any wrong going by the porsche community so they must be good.

I have other jobs done on my project c2 and most of it’s on my instagram if you want to have a look. It’s @nedhannon
Not everything has to cost a fortune Wink
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 17329
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Sat Jan 11, 2020 5:49 pm    Post subject: Reply with quote

What tyres are you running all round and what condition are they in. Makes a big difference on what the handling is like with regards ti under/oversteer.
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2000 Manual 996 C4 Arctic Silver Convertible


 
  
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Robertb
Dijon


Joined: 01 Sep 2003
Posts: 7587
Location: South Oxfordshire

2002 Porsche 996 Carrera 4S

PostPosted: Sat Jan 11, 2020 6:35 pm    Post subject: Reply with quote

Maybe try some geometry changes first before shelling out for new parts... I’m a recent convert to Center Gravity having had a suspension health check last weekend (and I went with scepticism shields full up!). Chris tweaked the toe slightly and it’s astonishing how different it feels. I will be returning for a full set up. Other suspension specialists are available but it certainly opened my eyes to how these cars chassis are like precision instruments.

It seems the factory settings are ‘one size fits all’ with a margin of safety and there is lots that can be done to set the car up to your preference.
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"911- the guilt-free supercar"

Current: 2003 C4S Coupe, seal/black

Ex: '02 C4S Coupe, '96 993 Targa, '88 Carrera Sport Coupe
 
  
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Martin996RSR
Nürburgring


Joined: 08 Dec 2016
Posts: 469



PostPosted: Sat Jan 11, 2020 7:43 pm    Post subject: Reply with quote

Smaller rear tyres, as most people fit stupid wide rear tyres. 265 section should be considered the maximum. Several folks on here run 255, including me, to get the rear to be less of a dominant partner in the front/rear grip balance.

Also, run the minimum rear camber you can get out of the suspension arm adjusters. Having MO30 will limit what you can get it down to, but this really helps. -1 degree is what you should aim for in order to get a rear end that actually works with you.

Adding negative camber at the front can help a little, but many people add far too much and it can really hurt straight line braking if you go OTT.

Regarding toe, you should dial out the toe on the rear to close to zero toe in. Toe out will make things even more fun(or dangerous, depending on your outlook), but at the price of rapid uneven tyre wear.

I've found that beyond adding a softer front anti-roll bar, there isn't much that can be done at the front, perhaps making sure you're not running too much toe in is worth the check.
 
  
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DarthFaker
Trainee


Joined: 13 Jun 2019
Posts: 93
Location: 1999 Carrera 4 Aerokit


PostPosted: Sat Jan 11, 2020 8:28 pm    Post subject: Reply with quote

Tyres are the most important thing for sure, I'm running Continental Sport Contact 5 all round, good condition. But tyres are quite expensive! I don't want to be changing them too often, so they'll be staying on until they're illegal Floor

I'll look into getting an alignment at Centre of Gravity before I physically change anything, as I know from racing what a few degrees of adjustment can do, I just wouldn't have thought the cars had enough range of adjustment in stock form.

I suppose it's worth a shot, it's hell of a lot cheaper than buying parts,

I'm sure Porsche engineered the suspension on these cars pretty well, it's apparent when driving them how well it handles bumps and the overall grip level (for a road car), it's just way too much under steer on the limit for me.
 
  
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skinny_monkey
Nürburgring


Joined: 16 Sep 2014
Posts: 488



PostPosted: Sat Jan 11, 2020 9:57 pm    Post subject: Reply with quote

What's your current geo?
You need to know what you're on before figuring out if you need more camber than you can achieve on stock parts.
 
  
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Robertb
Dijon


Joined: 01 Sep 2003
Posts: 7587
Location: South Oxfordshire

2002 Porsche 996 Carrera 4S

PostPosted: Sun Jan 12, 2020 1:37 am    Post subject: Reply with quote

DarthFaker wrote:
Tyres are the most important thing for sure, I'm running Continental Sport Contact 5 all round, good condition. But tyres are quite expensive! I don't want to be changing them too often, so they'll be staying on until they're illegal Floor

I'll look into getting an alignment at Centre of Gravity before I physically change anything, as I know from racing what a few degrees of adjustment can do, I just wouldn't have thought the cars had enough range of adjustment in stock form.

I suppose it's worth a shot, it's hell of a lot cheaper than buying parts,

I'm sure Porsche engineered the suspension on these cars pretty well, it's apparent when driving them how well it handles bumps and the overall grip level (for a road car), it's just way too much under steer on the limit for me.


Defo start with a visit to CG... I was encouraged to find that they are keen for you not to spend money you don’t need to.

Say what you want to achieve and they will tell you what you need.

It’s a fun day out too!
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"911- the guilt-free supercar"

Current: 2003 C4S Coupe, seal/black

Ex: '02 C4S Coupe, '96 993 Targa, '88 Carrera Sport Coupe
 
  
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 17329
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Sun Jan 12, 2020 8:01 am    Post subject: Reply with quote

Unless the suspension is pretty new you'll most likely need new rear coffin and toe arms as the eccentric bolts will be seized up in them preventing any rear adjustment.
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FZP
Estoril


Joined: 18 Jan 2015
Posts: 3971
Location: Cheshire


PostPosted: Sun Jan 12, 2020 11:05 am    Post subject: Reply with quote

CG have the knowledge to help you out. They also will most likely have parts on the shelf should anything need replacing pertaining to geo set up.
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Shalmaneser
Trainee


Joined: 11 Nov 2019
Posts: 65



PostPosted: Sun Jan 12, 2020 11:39 am    Post subject: Reply with quote

Martin996RSR wrote:
Smaller rear tyres, as most people fit stupid wide rear tyres. 265 section should be considered the maximum. Several folks on here run 255, including me, to get the rear to be less of a dominant partner in the front/rear grip balance.

Also, run the minimum rear camber you can get out of the suspension arm adjusters. Having MO30 will limit what you can get it down to, but this really helps. -1 degree is what you should aim for in order to get a rear end that actually works with you.

Adding negative camber at the front can help a little, but many people add far too much and it can really hurt straight line braking if you go OTT.

Regarding toe, you should dial out the toe on the rear to close to zero toe in. Toe out will make things even more fun(or dangerous, depending on your outlook), but at the price of rapid uneven tyre wear.

I've found that beyond adding a softer front anti-roll bar, there isn't much that can be done at the front, perhaps making sure you're not running too much toe in is worth the check.


Interesting post, thanks for this.

Are you running 255 on 10 inch rims? What profile have you gone for?
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Martin996RSR
Nürburgring


Joined: 08 Dec 2016
Posts: 469



PostPosted: Sun Jan 12, 2020 12:40 pm    Post subject: Reply with quote

I use 17" 10-spokes, the lightest OEM wheel for the 996 (though rarely seen on a 996, it was mostly used on the 993). Fronts are 7" and rears are 9" wide.

I can't remember what profiles the rears are, but pretty high. I find this helps the ride. I used to have Sport Design GT3 wheels, but they weigh a deal more and the 18" 285 section rears were not brilliant for ride or handling balance.

Check out ELA's CLR 996 build on here. He also uses 255 section rears on his very fastidiously developed car.
 
  
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Martin996RSR
Nürburgring


Joined: 08 Dec 2016
Posts: 469



PostPosted: Sun Jan 12, 2020 12:50 pm    Post subject: Reply with quote

Darth, a CG alignment costs in the region of £250. You're paying for their expert knowledge rather than their ability to turn a spanner or operate an alignment machine. However, with some research you can select your own settings and go to any decent tyre place and get a four-wheel alignment done for about £60. Cheaper still, you can use the string and axle-stand method that's still used today by touring car teams and align your car for pennies at home.

I'm not saying CG isn't worth what they charge, and I've never seen a dissatisfied customer, however they are not the only way to tune a suspension setup on our cars. I don't use them because I work on my car so frequently that I would spend as much on alignments as I do on parts.

This post isn't supposed to dissuade anyone from using CG, just to make them aware of their options.
 
  
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DarthFaker
Trainee


Joined: 13 Jun 2019
Posts: 93
Location: 1999 Carrera 4 Aerokit


PostPosted: Sun Jan 12, 2020 5:20 pm    Post subject: Reply with quote

I used to align my MX5 with nothing but a ruler, and string and it worked a treat. I just don't fancy going that ghetto on my 911.
 
  
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Martin996RSR
Nürburgring


Joined: 08 Dec 2016
Posts: 469



PostPosted: Sun Jan 12, 2020 8:04 pm    Post subject: Reply with quote

Nothing wrong with ghetto on a Porsche, so long as it's accurate. thumbsup
 
  
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 17329
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Sun Jan 12, 2020 10:06 pm    Post subject: Reply with quote

Grin
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2000 Manual 996 C4 Arctic Silver Convertible


 
  
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Dagerous
Trainee


Joined: 23 May 2014
Posts: 50
Location: Hamble


PostPosted: Sun Jan 12, 2020 11:28 pm    Post subject: Reply with quote

Darth you may be surprised at how much adjustment is in the 996 suspension!

Where are you based? If it’s anywhere near southampton there are a couple of good places that can do your alignment, either to factory settings or your own. I’ve absolutely nothing against Centre Gravity but it’s a long way away from me!

My C2 Aero used to run M030 but recently changed to Ohlins. Fitted and set up by Brookspeed’s Carrera Cup race engineers at GT3 ride height and about -1 degree front and -1.9 back. It has definitely improved the turn in. Dropping the ride height tends to naturally increase the negative camber anyway so maybe some lowered springs might allow a bit more negative camber. It might come at a cost to tyre life though. I told the engineers not to worry too much about tyre life as mine’s really just a fun / weekend toy.
 
  
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peterg1955
Silverstone


Joined: 09 Apr 2017
Posts: 124
Location: Berkshire


PostPosted: Mon Jan 13, 2020 9:45 am    Post subject: Reply with quote

Although I have a 2002 c2, this is what Chris at CG did for my setup as I said I wanted minimal understeer and it's worked very well over the last nearly 3 years and 12k miles
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Martin996RSR
Nürburgring


Joined: 08 Dec 2016
Posts: 469



PostPosted: Mon Jan 13, 2020 11:00 am    Post subject: Reply with quote

That's a very symmetrical alignment - very hard to achieve and a testament to the guys at CG.

It's also pretty close to my recommendations above, i.e. modest camber and only minimal toe in.
 
  
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MJA911
Sepang


Joined: 10 Dec 2013
Posts: 2871
Location: Berkshire

2012 Porsche 991 Carrera

PostPosted: Mon Jan 13, 2020 1:33 pm    Post subject: Reply with quote

Spot on with the observation about tyres and also CG. I was there Saturday for the health check on my 991. Firstly the car tried to plough on rather than go round the mini-roundabout they use on their test route, immediately diagnosed as the 5 year old pzeros have gone hard (even though they have plenty of tread), the test drive also revealed drift to the left under acceleration on the straight, diagnosed as geo/cambers not quite symmetrical, proven on their machine when we got back. A CG optimised geo and new tyres will likely make a huge difference.
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991.1 C2, 986 Boxster S
Past pleasures: 997.1 GT3, 997.2 C4S Cab, 993 C2, 997.1 C2S, 996.1 C4
 
  
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