Suspension upgrades for Cayman T

[GregThoma]

Hi All,

Appreciate your advice, can't seem to find the suspension recommendations for 718 Caymans with SPASM.

The car is used for trips and track days. What I am finding is that when I maximised the current geo the car becomes very lose and grip goes. The reason for trying to improve geo set up is that I am destroying the edges of the tyres.

Before Geo the car was solid at

Front Left -1.05 Right -0.92

Back Left -1.85. Right 1-.98

After Geo the car was more pointy but the back became twitchy and felt Like I had lost grip mid corner.

Front Left -1.28 Right -1.30

Back Left -2.03. Right -2.01

Could not believe that a small amount of change made such a difference. The car was all over the place and with the previous set up the car felt nailed to the ground. Maybe I need to change the way I drive but it felt alien and way slower, no confidence.

Back to set up below and chewing up tyre edges.

Front Left -0.95 Right -0.96

Back Left -1.79. Right -1.79

So have read a lot on LCA’s, Ohlins and KW V3 suspension. The brief is, occasional trips and drive to and from track days, it is not a daily, like the idea of keeping SPASM but open to suggestions. Some Porsche tuners are not interested, get a GT4 is the theme.

Hope to hear from people soon.

 

[mr pg]

Have you checked your toe setups? Excessive toe can also eat tyres.

 

[GregThoma]

Thanks for the suggestion these are the current values.

Front Toe Left is 0.05 and Right is 0.03
Total Toe is 0.07

Rear toe left is 0.13 and Right is 0.15
Total Toe is 0.27
Trust Angle is -0.01

 

[Motorhead]

Hi Greg,

I’m no suspension expert but although the front toe probably is about right, that sounds like a lot of rear toe [out?] which could be a cause of your instability together with excessive rear tyre wear on the inner edges if that’s what you’re experiencing.

I don’t have the base geometry set-up for your car but this link could be of interest for reference:

https://www.718forum.com/threads/stock-suspension-geometry.21050/

If you contact your local Porsche dealer they will be able to provide the stock target values for your car.

Jeff

 

[GregThoma]

Thanks Jeff, that has really helped me understand more of the challenge. Appreciate the information.
Cheers Greg

 

[carreraboy]

Don't forget can always contact Ollie Preston at RPM Technik, his details in Porsche Post Modified Section.

 

[Twinfan]

I've had a few geo setups on my Caymans and have found:

* More negative camber on the front than the rear works best - aim for a 0.5deg difference. Shims can be added to the front to help with this. I think -2deg front and -1.5deg rear is a nice medium setup.
* Very, very slight toe-in on the front helps keep the tyres heated and grippy. Toe out is super aggressive and likely too much for a car used regularly on the road. I run 0.01 each side.
* For stability under braking a lot of rear toe-in is best. I run the maximum recommended setting of 0.14 per side but I do have non-standard rear toe links. If you want to stay OEM, run as much as you can with the camber setting you're aiming for.

Looking at your numbers, I think you have too much front toe and too much rear camber. I'd be tempted to invest in a couple of shims for the front and aim for something in the region of

-2*00' camber on the front
+0*02' total toe-in on the front (+0*01' per side)
-1*30' camber on the rear
+0.28 total toe-in on the rear (+0*14' per side)

I ran something similar on my 981 GTS and at first on my 718 GT4. The car felt good and tyre wear was acceptable.

I hope that helps!

 

[Twinfan]

Oh, and I forgot to mention tyres and pressures. 30F/33R hot is a good starting point, then adjust to taste.

Heat cycles eventually cook the tyres and they loose their suppleness, becoming rock hard and low in grip. If you've done more than say 5 full track days and plenty of sessions on them you might want to consider replacing them, even if they have plenty of tread left.

 

[GregThoma]

Thanks everyone for your advice went to 9E, LCA's from RSS and shims, car feels very stable and agile. Looking forward to next year and some track days.

 

[GregThoma]

I've had a few geo setups on my Caymans and have found:

* More negative camber on the front than the rear works best - aim for a 0.5deg difference. Shims can be added to the front to help with this. I think -2deg front and -1.5deg rear is a nice medium setup.
* Very, very slight toe-in on the front helps keep the tyres heated and grippy. Toe out is super aggressive and likely too much for a car used regularly on the road. I run 0.01 each side.
* For stability under braking a lot of rear toe-in is best. I run the maximum recommended setting of 0.14 per side but I do have non-standard rear toe links. If you want to stay OEM, run as much as you can with the camber setting you're aiming for.

Looking at your numbers, I think you have too much front toe and too much rear camber. I'd be tempted to invest in a couple of shims for the front and aim for something in the region of

-2*00' camber on the front
+0*02' total toe-in on the front (+0*01' per side)
-1*30' camber on the rear
+0.28 total toe-in on the rear (+0*14' per side)

I ran something similar on my 981 GTS and at first on my 718 GT4. The car felt good and tyre wear was acceptable.

I hope that helps!

Thanks for the information, when you state its better have more negative camber at the front, is that so you can get the back to rotate more easily.

 

[Twinfan]

It's because you push the edges of the front tyres more than the rears in corners. More camber at the front means they distribute heat and wear across the width of the tyre more similarly to the rears.

 

[GregThoma]

It's because you push the edges of the front tyres more than the rears in corners. More camber at the front means they distribute heat and wear across the width of the tyre more similarly to the rears.

Yes understand better distribution and even tyre wear, does having more negative camber at the front mean more grip at the front than the back. Does this make the car a little more tricky when handling.

 

[Twinfan]

More camber at the front gives more balanced grip on track, not more grip at the front than the rear.

Think about the tyre, and how flat you want it to be, front and rear, through corners. The front gets pushed harder than the rear, hence the need for more camber up there.

On the road this really doesn't make a lot of difference but at track speeds it does.

 

[Motorhead]

Greg,

Just to add that camber is reduced [becomes more positive] as the front outer wheel gets loaded in a corner and so more static negative camber reduces this effect, and as Dave says this gives a more even load and heat distribution across the tyre contact area.

Jeff

 

[GregThoma]

Ok great, I was over thinking it, I'll get the XL toe steer arms for the front next year, currently have -1.5 front(was -0.6) and -2.0 at the rear. The car at moment feels great,very planted and agile. So will do a couple of track days and then tweak the front. Thanks again for your help.