Mike in CA

I got my car back this morning from having an alignment done to adjust camber settings. I was looking for more negative camber front and rear with minimal changes from stock to the other settings. The numbers shown were achieved within the normal range of adjustment; no shims or other mods were required.

I was surprised by a couple of things. First, more negative camber was achieved than I expected; a bit over 2.5° at the rear and about 2.25° at the front. The changed stance of the car is visible to the naked eye, especially at the rear. The second surprise was how far off the factory alignment was from spec, with significant variations from side to side.

I'll have to wait for the autox next weekend to really test the results although through some nice twisties near my home the car felt very nicely planted and more stable; maybe just my imagination.

Anyway, I thought this might be of interest. Sorry if similar info has been reproduced elsewhere although I looked....was too lazy to do a really long search!

ipse dixit

Thanks for posting, MiCA.

Would love to get your thoughts on how the tires wear with max negative camber. You have MPSC2 right?

kyrocks

Yes, I agree, you can get that much negative camber with stock equipment. Still not as much as the 997 though. You need to be careful with caster when you add a lot of camber, your value of 9.5 is actually good. The 991 tends to go over 10 with a lot of camber.
Why the negative and positive toe in the rear? What direction is your autocross? Thanks.

kyrocks

Sorry, misread the rear toe.

Mike in CA

I do have MPSC2's. They're maybe 50% worn but the wear has been pretty even across the tire so far. I'll be curious to see what effect the camber adjustment has either on this set going forward or on the next one and will post results.

No worries. FWIW, sometimes our courses are set up (mostly) clockwise, and sometimes counter clockwise. Yeah, I'm no expert on the subject but my understanding is that the 997 allows the front struts to be rotated to achieve a different range of settings while on the 991 there is only the range allowed by the eccentric slots. I don't know what the story is at the rear....

seapar

I have about - 2.2 front and rear set up by Cantrell's. My wear is even and I have tracked 5x . Similar as initial setup as SmokinGTS but I think he added more camber recently. I am not as fast or aggressive as most of you. Mix of DD and track.
Btw I don't feel any tramlining DD on freeway at all.

Macca

Mike this is a curious subject. I have over a dozen Geo sheets from 991 GT3 owners around the world including my own and I make the following observations:

1). maximum camber available varies from -2.0 to -2.2minutes typically. Of course variance may be down to operator and equipment used.

2). Ive yet to see a car even immediately after factory delivery read less than 9 degrees castor when the factor spec sheet says it should be 8.5!

A few comments on your sheet. Something does not seem right.Your front castor figures haven't changed even with a significant change in front camber (left wheel as example). Also your "before" cambers seem way out. Maybe the operator did not record initial measurements correctly.

I also suspect (and I am shortly to determine) if the settings with this car fall out of alignment quickly as they do on earlier cars such as my 993. I say this because you have had the car well over a year and its possible that the alignment has changed in that time. Its very easy to upset these settings. Usually a pothole or hitting a curb but Ive had the settings come out on the 993 just from repeated track days (the odd spin in the wet onto the grass probably doesnt help). Potentially work on the front lift have a bearing on this is for example some warranty work was carried out but the struts not aligned afterwards. I know that is not the case for you. This is a very stiff chassis - I lift a front AND back wheel when departing my local gas station. Its always a possibility your car was delivered at -1.30 but that it has fallen out of alignment. Its interesting its on opposing corners...

SamFromTX

Thanks for posting Mike. Interesting that your alignment was off too. Macca, my car's alignment was out of spec in 3 out of the 4 wheels when I took delivery. I asked if the alignment would then be covered under warranty and they said that if it was to be corrected, yes but since I had him adjust further away from spec, no.

Macca

Sam. maybe they leave the factory just fine but strapping them down on the ship or the transporter screws things up? Ill be making it an annual thing to have my geo checked and re set. Im pretty sure with the fast back road driving I do and the state of our roads its would be a reasonable investment.

Mike in CA

Mark, you have a good eye and I think you are spot on. I'm almost certain that there was some operator error involved in the starting data entry for the front axle. The technician has a great deal of experience doing track car alignments but the dealer just got a new machine and I think unfamiliarity with it may have been a factor in the initial castor values he entered.

Your other comments about how values may have changed since the car was new are also valid. Regardless of whether they've changed with use it was still surprising to me that they were so far out of whack. As you say, it will be interesting going forward to see how sensitive this car's alignment is to road conditions.

Alan C.

seapar,

0.52 total toe in the rear is the most I have seen. Curious to see how that works.

seapar

^ I think that was the before. Much less after 0.31.
SmokinGTS also had 0.47 rear toe before.

DMoore

With my 997.2 GTS I maxed out the available negative camber, both front and rear. I don't recall the actual numbers but both F and R were less than is available on the GT3. I, like you, ended up with more neg camber in rear than in front.

My experience was that the car's handling went to hell. Talk about understeer! Everything I've ever seen about Porsches, regardless of model, is that the rear camber should not exceed, and should probably be a little less, than the front. I've been wrong before but I'll be interested to see what you think when you drive it. I won't be surprised if you don't end up dialing down the neg camber in back.

My GT3 is set, as a road/track compromise, at -2.1F/-1.8R. I've gotten about 4 track days out of my MPSC2's so far, with at least another day's worth left in the tires. It feel very balanced and significantly improved my AX results from the factory settings.

DMoore
'15 GT3
'13 Panamera GTS

Alan C.

seapar,

Thanks, that is a lot of rear toe from the factory.

Mike in CA

Based on my experience with my previous 997.2 S I started out by having just the front adjusted to about -2° and left the rear alone. To my surprise, the car seemed a bit tail happy. I felt I needed more grip at the rear so that's why I'm trying this setup, although to be honest they managed a bit more camber than I expected.

I think what may differentiate the 991 GT3 from the 911's that came before it is RWS, but obviously you still feel there is an issue with understeer. I personally think this 911 turns in better than any other I've owned. Anyway, the car felt really good on the road today and I think I can adjust for any issues with tire pressures but we'll see how it works out.