996 C4 - Dialing out some understeer.

DarthFaker · 11 Jan 2020

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.

NedHan79 · 11 Jan 2020

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:

Alex · 11 Jan 2020

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.

Robertb · 11 Jan 2020

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.

Martin996RSR · 11 Jan 2020

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.

DarthFaker · 11 Jan 2020

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.

skinny_monkey · 11 Jan 2020

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.

Robertb · 12 Jan 2020

DarthFaker said:
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!

Alex · 12 Jan 2020

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.

FZP · 12 Jan 2020

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.

Shalmaneser · 12 Jan 2020

Martin996RSR said:
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?

Martin996RSR · 12 Jan 2020

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.

Martin996RSR · 12 Jan 2020

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.

DarthFaker · 12 Jan 2020

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.

Martin996RSR · 12 Jan 2020

Nothing wrong with ghetto on a Porsche, so long as it's accurate. :thumbs:

996 C4 - Dialing out some understeer.

DarthFaker

Trainee

NedHan79

Suzuka

Alex

Nordschleife

Robertb

Yas Marina

Martin996RSR

Montreal

DarthFaker

Trainee

skinny_monkey

Montreal

Robertb

Yas Marina

Alex

Nordschleife

FZP

Zandvoort

Shalmaneser

Montreal

Martin996RSR

Montreal

Martin996RSR

Montreal

DarthFaker

Trainee

Martin996RSR

Montreal

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