991 GT3 Geo settings. Caster?
991 GT3 Geo settings. Caster?
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Discussion

5517

Original Poster:

1,953 posts

268 months

Saturday 14th February 2015
quotequote all
I had my geo set to standard factory settings yesterday.

first point is that my 3k mile car was wildly out of shape!!!

and second point is that the caster is not adjustable and yet it is considerably out of tolerance.
7.30-8.30 is range and it is 9.19 and 9.29.

Thoughts please gentlemen?

Slippydiff

16,009 posts

246 months

Saturday 14th February 2015
quotequote all
5517 said:
I had my geo set to standard factory settings yesterday.

first point is that my 3k mile car was wildly out of shape!!!
No big surprise there I'm afraid, contrary to what most think/expect of a new Porsche GT car, most are out of alignment and the rear ride heights too low/front to rear rake incorrect.
The springs will settle after the car is built. I'd to expect to have to do a ride height/geometry check six months after delivery to ensure all is correct

5517 said:
And second point is that the caster is not adjustable and yet it is considerably out of tolerance.
7.30-8.30 is range and it is 9.19 and 9.29.

Thoughts please gentlemen?
See the link to "Caster adjuster" on this page :

http://www.elephantracing.com/suspension/controlar...

http://www.elephantracing.com/suspension/bushings/...

Looks like you'll be kissing your warranty goodbye if you fit them though......


Explanation of Cup car and 991 GT3 caster adjustment/lack of adjustment can be found here :

http://www.elephantracing.com/tool-box/specs/991/C...



Kawasicki

14,131 posts

258 months

Saturday 14th February 2015
quotequote all
yes, check ride heights...

sidicks

25,218 posts

244 months

Saturday 14th February 2015
quotequote all
Has anyone taken their 991 GT3 to Chris @ Centre Gravity to have the settings reviewed and, if appropriate, adjusted?

I'm not sure I've spent enough time with the car yet to seek a particular adjustment, but at least confirming that the settings are within specification would be helpful.


5517

Original Poster:

1,953 posts

268 months

Saturday 14th February 2015
quotequote all
So this was before...


and after...


The geo settings in the drivers manual show zero toe on front which Im told is very odd.
The geo settings direct from Porsche to the geo computer are different.

Should i complain to Porsche about the caster issue?

Slippydiff

16,009 posts

246 months

Saturday 14th February 2015
quotequote all
Ride heights weren't checked I presume ?

mollytherocker

14,400 posts

232 months

Saturday 14th February 2015
quotequote all
Surely Porsche have to get your castor settings correct? Whatever it takes?

sidicks

25,218 posts

244 months

Saturday 14th February 2015
quotequote all
Slippydiff said:
Explanation of Cup car and 991 GT3 caster adjustment/lack of adjustment can be found here :

http://www.elephantracing.com/tool-box/specs/991/C...
A very interesting discussion, but I thought this comment was most telling:

"The two cars are surprisingly very similar to each other as far as the suspension goes. This generation of GT3 is closer to the Cup car than a standard Carrera; closer than previous versions of the GT3."

biggrin

nxi20

782 posts

228 months

Saturday 14th February 2015
quotequote all
5517 said:
The geo settings in the drivers manual show zero toe on front which Im told is very odd.
Zero toe isn't all that unusual. I run zero front toe on all of my GT cars & it gives you great steering feedback without being too twitchy on the road. Toe out is great on a pure track car but a bit lively for road use! The more toe in you run, the more stable the car is, particularly at speed, but you lose more steering feel & the car isn't so eager to turn in. Set up according to taste.

More caster will give you a stronger steering self-centre tendency & can often aid front-end grip due to increasing the camber gain when cornering. The only real downside of more caster is that you will need more steering effort to overcome the self-centreing forces. Your caster is a way past the optimum angle though, so I'd suspect that the car is running lower ride heights than it was designed to. This will have the tendency to increase the caster angle.

5517

Original Poster:

1,953 posts

268 months

Saturday 14th February 2015
quotequote all
Slippydiff said:
Ride heights weren't checked I presume ?
No this was a simple £80 alignment done as a last minute thing prior to tracking the car for the first time today.



5517

Original Poster:

1,953 posts

268 months

Saturday 14th February 2015
quotequote all

5517

Original Poster:

1,953 posts

268 months

Saturday 14th February 2015
quotequote all
nxi20 said:
Your caster is a way past the optimum angle though, so I'd suspect that the car is running lower ride heights than it was designed to. This will have the tendency to increase the caster angle.
Thank you, great input.

Where are the "factory" height details found?

Slippydiff

16,009 posts

246 months

Saturday 14th February 2015
quotequote all
Ride height, and the datum points used to set them will be within the technical data accessed on line ? by the technicians. It's downloadable by the technicians, but I think they have to log on to the system using their own unique access code, once they've done so any information they download/print off has their name emblazened across it .....

Where did the above information for the toe and camber settings come from ?


Slippydiff

16,009 posts

246 months

Saturday 14th February 2015
quotequote all
sidicks said:
A very interesting discussion, but I thought this comment was most telling:

"The two cars are surprisingly very similar to each other as far as the suspension goes. This generation of GT3 is closer to the Cup car than a standard Carrera; closer than previous versions of the GT3."

biggrin
Hmmmm, where to start ........

ArcticGT

984 posts

235 months

Saturday 14th February 2015
quotequote all
It's soo close they don't even need to share an engine tongue out

sidicks

25,218 posts

244 months

Saturday 14th February 2015
quotequote all
ArcticGT said:
It's soo close they don't even need to share an engine tongue out
What has that got to do with suspension?

mollytherocker

14,400 posts

232 months

Saturday 14th February 2015
quotequote all
ArcticGT said:
It's soo close they don't even need to share an engine tongue out
Or the bodyshell....

5517

Original Poster:

1,953 posts

268 months

Saturday 14th February 2015
quotequote all
Slippydiff said:
Where did the above information for the toe and camber settings come from ?
page 203 of the drivers manual in your book pack.

Slippydiff

16,009 posts

246 months

Sunday 15th February 2015
quotequote all
5517 said:
page 203 of the drivers manual in your book pack.
Well you now need to find out what the front and rear ride heights are and the datum points for them.

kbooker

728 posts

162 months

Sunday 15th February 2015
quotequote all
A friend is an Ohlins specialist, he always comments that Porsche are the worst offenders for incorrect alignment from the factory...