doc2s

total is the sum of both sides. if you were ever quoted the total toe you need to know the side-to-side difference to be sure that both sides are equal or very close.

Apex Late

Supercup,

Thanks for the post and please forgive my ignorance here. I understand your thoughts with reference to camber and toe. However can you tell me how they relate to ride height? I noticed that on your cup car you are running a higher rear end (unusual as the 996 version liked a little lower rear end realitive to the front) and on the street car the PASM needs to be level to work properly. I originally tried to have a little rake in the car as I did with the 996 but it jumped off the road when I hit the bumps. I currently have the car as low as it will go without being too low for the suspension. Aprox 1 inch from stock.

Additionally you have suggested 34' of toe in for the rear. Is that not a ton of toe? I understand that it will make the car more stable but there isn't a stability issue right now with 10'??? Can you please explain?

supercup

Unfortunately I cannot explain as I am not a tech or an engineer. I just drive em and this is how they have been set up.

The spec's I noted are out of the 997 Cup Service Manual as factory specs.
The 996 factory spec for the Cup called for 86mm ride height in the front and 107mm ride height in the rear.

You would be much better off getting a good race shop to help you. Sorry I can only supply some factory data that I have.

JCM

Bob Rouleau

Apex - the 34' of total toe in the rear is the setting I got from Roland Kussmaul. He suggested it for the GT2 and 3 which have the same chassis.

I agree that the 996GT3 was more inclined to wag the tail than the 997 version which is totally planted in back .. so much so that it would not turn in at Calabogie. Did you try the car with TC off and sport mode not selected? I did the former (it helped) but not the latter. I have to re-read the manual tonight but I think that Sport mode does something to the suspension as well as changing throttle response and the muffler flaps.

What puzzles me was that the car did not exhibit any bad habits when I ran it in the rain at St-Eustache. The bars were in the as delivered settings. I ran with Sport on and TC on. Handled like a dream. The grip really surprised me. A good set up for a wet track would normally be too soft for the dry and yet here we are thinking of making the roll bars softer. Odd.

Note that the 997 CUP does not have PASM as far as I know. Who knows what the electrons are doing at the 4 corners of the car while we try and coax it into the apex.

Lastly - I would be wary of big negative camber on 12 inch rims. I tried it on my GT2 (with 12 inch wheels) and cut the inside edge of the tire right through in only a few hundred miles of street driving. The wider the wheel the more you tend to pressure the inside edge of the tire with aggressive negative camber. I needed a flat bed because the tire flat goo does not work on a tire which has been sliced into two parts!

Best,

Apex GT

Bob, Sport mode does activate the PASM

insite

running a wedged ride height will reduce understeer. it also has the effect of adding some downforce to the rear of the car at speed.

34' is more than i would personally run. maybe on a high speed oval or something....i can't speak to the 997, but in the 996 i like about 1/8" total toe in back for most courses.

frayed

I think you mean doesn't? Sport mode opens up the exhaust, doesn't **** with pedal response, and extends TC limits IIRC. Doesn't do anything to PASM and I don't think you can turn PASM off. That is, you gotta physically disconnect the PASM electronics and car will go into PASM limp mode.

Racerron

Hi All,

If I may jump in! For sure, I think that reducing the rear toe-in may help, and of course giving toe-out will help at front, but my experience with the car at the same track and time as Bob and Apex is that the initial turn in was fine (front toe-out will only help with initial turn in) but the car would just not rotate without having to do stupid stuff like jump off the gas while turning and trail braking.
I tried left foot braking which helped a lot but I need more npractice with that.
Compared to the 996 GT3 where, you only had to think about the apex and the car would turn, in the RS is a pig for understeer. I think, and maybe someone can help us out in this regard, is that the Euro RS's are sprung differently than the US models. Obviously Porsche knows of the gross understeer problem because the as delvered settings for the anti-roll bars was full stiff in rear and one from full soft in front.
To see the video of the Porsche test driver drifting the car through the turns, makes me think that either that was a specially set up car, or the Euro spring specs are WAAAAAAY diferent.
I could not get the rear to budge at all, it was just plain stuck. I only had the rear end loose once the whole week-end in "Temptation" Bob and Apex will know where, and that was by really stabbing the brake just before the turn in for the apex, again left foot braking. All this should not be necessary in a car marketed by Porsche as a track car that may sometimes be used on the street.
As for -3 degrees, I agree that this may help although, it didn't help Apex, but holy crow don't drive too far on the street, with those settings.
On the 996GT3 I only run -1.5 front and -2 rear, and can keep up with most with those settings. Tire wear is very acceptable as well.
Changing the rear spring rate alone may not be the best idea because of the SPASM (Stupid Porsche Active Susp. Management) Can the SPASM be disabled with the PWIS, I doubt it.
Maybe a 250lb. increase in rear rate would help and then there is plenty of room on the bars to tune out any excessive oversteer (I wish)

Just my 10 cents.

MetalSolid

Could all this be due to the LSD?

frayed

A less aggressive LSD causes less understeer, not more.

Racerron

It's my belief the LSD in the RS is set way lower than the 996GT3 because of the rear end sensitivity problem (read crashes) reported by the gold chain set, as well as the "the car is too stiff and unconfortable for my wife to drive in it" complaints.
I have never figured out how full leather and deviated stitching made the car perform better, but Porsche sure does push the option list. The one I really love is the leather covered dome light surround...WOW that must be good for a second a lap.
I particularly like the flashing symbol on the dash that tells the operator of a GT3 or RS that you have a flat tire, when you have only dropped the tire pressures to suit the installed track tires. There should an OFF button for that. Or an extra menu item so that it would read Summer, Winter or Track tires.

PORSCHE!!!!!!!!!!!!!! Listen to your true fans and cut the option and electronic crap and build a super fast car that is great on the track in capable hands and just okay on the street. I promise not to sue you if I crash the car because I ran out of talent.
I know, make it a limited production version of a current model with no frills and let the potential buyers know exactly what they are getting so that, the cruisers and non trackies can buy the regular (Cadillac suspension) version. Oh, I'm forgetting that is what the RS was supposed to be but somehow it got lost in the trip over the Atlantic and was replaced by a C4S with a GT3 engine. ( No offence intended to C4S owners )

Unitah

As far as a difference between Euro GT3's and US cars, there is no difference in springs or shocks, or anything. Alignment is the same as well. I just returned from Leipzig the other day. I rented the track and Porsche's chief racing instructor and a GT3 for a few hours. Let me tell you, none of us have ANY idea what the hell we are doing. After seeing this guy drive, hahaha, we are all merely varying shades of bad, hahaha, including myself (and I thought I was doing well)! I never saw anyone with so much car control, talk about sliding, how's 145mph with the *** WAY out, wow. Incredible. And this guy was so comfortable, it was like a sunday drive for him.
Anyway, I asked him about car setup, he said it was dead stock. After inspecting the car a few times, I can tell you, there was NO visible camber in ANY wheel. Simply amazing.

Bob Rouleau

Unitah - while not up to the level of the factory driver, I an hang the tail out without a problem. In fact, Apex and I found that jumping off he gas and "rotating" the car (that's short for hanging the tail out) was the only #@!! way to get the car pointed to the apex of Wilson (to name one).

frayed

Great post. Must have been an amazing time.

cosmos

I did not even know you could rent out the track and an instructor?? Nice!!