I just did my first event in my new (to me) 2002 QS Zo6 this weekend. I have about 15 years of track driving under my belt in Porsches, shifter Karts and Motorcycles. The ZO6 is totally stock, including tires and here are my impressions of it in general and also with Competitive driving mode on and off.
First, I had my tire pressures TOTALLY wrong for the first session. I had them at 32 psi cold (recommended by someone who suposedly knew what they were talking about!).... The first lap and a half the car felt pretty awesome, however by the second time around it felt horrible... by lap three, it was absolutely undriveable; completely sideways everywhere (I mean sideways in fourth on the main straight!!!) and I was scared sh**less. I have NEVER been so badly out of shape in anything (Car, Shifter Kart, Motorcycle) ever.
On lap 4 coming over the hill through turn 9, I was changing to fourth and trying to get back on the throttle when the rear of the car went about 45 degrees to the left and the competition mode kicked in HARD... the car straightened out and I decided that there was NO WAY that the car should be this bad, I used more driving skill than ever before in my life just to keep the damn thing on the track.
After getting to my pit, I checked my tire pressures and they had gone up to 52 psi!!! They were also totally melted and chunked in a couple of place. I waited about an hour for the tires to cool down and set the pressures at 25 psi. Next session it was COMPLETELY 1000% better (thank God). I tried this session with competitive mode on and by the time I have done about 6 laps, I found that it was definitely interfering with what I was trying to do. Through turn 2, which is a looooooong 3rd gear left hander, it kept trying to correct the car where it didin't need to be corrected! You try to get through turn 2 which is a decreasing radius turn by tightening your line, coming from about halfway out, towards the apex and it means that you have to balance the car right on the edge of adhesion without having the rear end come around on you, it's a very delicate balance to get it right... The competitive driving mode didn't like this and kept cycling through each wheel, screwing up my corner speed and even worse, it was causing major understeer. With it off for the next lap, all of a sudden, the car was doing what it should have been and was going where I pointed it.
In general terms, I wanted to drive the car totally stock, just to get a feel for what I need to change first for tracking it. First thing on my list is wheels and tires. If there was ever a car that was in dire need of decent tires for the track, this is the car! If I had kept driving it at full chat on those Michelins, I would have completely destroyed them in about 6 hard laps. I found out that the car understeers heavily in lower speed corners... I had a bugger of a time getting through the chicane (turns 11 and 12), it understeered heavily, followed by snap oversteer when the fronts decided to grip again. The good news is that it is brilliant through the real fast stuff on the back section (6,7,8,9). I can be flat on the gas, no lifting all the way through, with the car just four wheel drifting controllably between 7 and 8 (the car was just FANTASTIC here, just one of my favorite series of turns anywhere) hitting around 115 -120 before braking for 8 and 9.
So compared to my 944 Turbo, with a $40,000.00 engine (and 6 or 7 blown headgaskets), full race coilovers, 14" Brembo "Big Reds", 275/35-18 fr, 305/30-18 rear Hoosiers, -3 degrees camber in front, -2.2 degrees in rear and a massive amount of money and track time into it, I can tell you that this ZO6 has WAY more potential to go fast. I couldn't be happier with the car and will be doing the following to it one stage at a time.
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CCW one piece Corsair forged 18 X 11 Fr, 18 X 12 rear with Hoosier R6's 315/18-30's fr, 335/18-30's rear.
Brake ducts, fron and rear
6 piston calipers with 14" rotors up front, 13" 4 pistons in rear.
Vortex intake
LG Pro Long tubes, x-pipe, high flow cats all jet-hot coated, stock muffler.
F.A.S.T. intake manifold
Higher flow injectors
Underdrive pulley set
AFR 205 heads
Super secret cams (street legal in CA)
Double roller cam chain with tensioner upgrade
Delrin bushings, new metal link tie-rod ends
SS brake lines
172 degree Thermostat
Body stiffening plate
T1 trans cooler kit
T1 Sway bars
New high capacity Aluminum Radiator with built in oil cooler
Synthetics all throughout, including transmission/diff.
If I can't go faster with all of that done that I did in my 944 Turbo, then I'm old and I suck
The Michelin Pilot Sport 2's. By the time I had done three sessions, the hot temperatures were 34 front, 32 rear, which felt pretty good. If I had more time, I would have reduced the pressure in the fronts to see if it cured the brutal understeer in the slow corners, I might have tried 30 psi in front just as an experiment.
As mentioned, the OEM tires are Goodyear F1SCs and I've tracked on them many times and would suggest starting the Goodyears at about 32F, 30R. No experience on the Michelins. I know my Kumho V710s like lower pressures than the Goodyears so it doesn't surprise me too much that your Michelins didn't like 32#.
Looking at your list of mods, I'd suggest that you pin the crank the first time you take the front off. I found out the hard way that the stock balancer doesn't like to stay on after it has been pulled off and put back on once or twice.
As mentioned, the OEM tires are Goodyear F1SCs and I've tracked on them many times and would suggest starting the Goodyears at about 32F, 30R. No experience on the Michelins. I know my Kumho V710s like lower pressures than the Goodyears so it doesn't surprise me too much that your Michelins didn't like 32#.
Looking at your list of mods, I'd suggest that you pin the crank the first time you take the front off. I found out the hard way that the stock balancer doesn't like to stay on after it has been pulled off and put back on once or twice.
I'm used to the Hoosier RS03's and they worked fantastically at 36 F, 34 rear hot, I have a couple of buddies running the Victororacers and they seem to like 32 F, 30 rear. 32 f, 30 r hot seems like it would do the trick, however, I will not run street tires at the track again... Back to the Hoosiers (R6's) for me!
You will need to do mini tubs to fit 12' rear wheels, or they will stick out far from the body work. Then, you can crack the fender if you hit a big bump. I'm running 11 1/2 inch CCW classic race rear wheels with a .190 spacer and 335-30 x 18 tires. This combo works for me, and without mini tubs. I had to trim the outside of the rear air ducts to clear the inner wheel rim. CCW recommends removal of the ducts, but I didn't want to loose all the cooling. Hoosier recommends 12' rims for the 335-30s but the sidewall looks very supported by the 11 1/2s, and I have no ill effects during use. Wear patterns are normal, and the car is very controllable. You could call CCW... I think they are very experienced with dimensions and fitting issues for C-5s.
thanks for the input. I talked to CCW and they also recommended the mini-tubs, so I will definitely do it. I am being told that there is no issue whatsoever with 315's in front, so it looks like I'm all set! My next track day is in about 6 weeks, so the only thing I will have changed will be the wheel tire combo, that way I will be able to feel the difference from just that one change. The next thing will be CAI, then headers etc.
I am being told that there is no issue whatsoever with 315's in front, so it looks like I'm all set!
I run 315/35-17 on 17x10 fronts in SCCA T1, but have minor rubbing issues, primarily with the top dead center lip of the fender which rubs on the top of the tire with the suspension under heavy compression. Really hard to see unless you get really close or run your fingers along the lip of the fender. Depending on how you feel about that, you might want to consider something slightly narrower as the 315s do stick out the side a half inch or so.
I run 315/35-17 on 17x10 fronts in SCCA T1, but have minor rubbing issues, primarily with the top dead center lip of the fender which rubs on the top of the tire with the suspension under heavy compression. Really hard to see unless you get really close or run your fingers along the lip of the fender. Depending on how you feel about that, you might want to consider something slightly narrower as the 315s do stick out the side a half inch or so.
Subdriver... How much negative camber are you running in front? On my 944 Turbo, I ran -2.5 degrees in front which made the difference between rubbing and not rubbing (-1.8 degrees rubbed), also, the 315/35-17 is a little bit taller than the setup I'm proposing 25.68 inches vs stock at 25.34 inches and 25.4 inches for the 315/18-30's. Another thing, what offset are you running?
i had very similar experience on michelin ps2 yesterday (first time at the track with this tire) - set the cold pressures same as I used to put in f1 supercars (36 front/34 rear, cold) and it was drift city after second lap! VERY SCARY. I kept taking the air out, eventually settled where the car would behave MUCH better, but I still had to cool down every 20 minutes as rear would get swingy in the middle of the turn. I am going to check cold pressures today to see what I finally settled on. Next time I go i would probably take out another .5 psi out.
The good news is that thread surface and outside edges were in MUCH better shape compared to goodyears exposed to the same track. It might also have something to do with the design of the surface, michelins have much more "rounded" edges.
Bottom line - if you track on ps2s, watch your pressures carefully and don't go in too deep in the first few laps - these tires can definitely surprise you.
UPDATE: the "final" cold pressures were 31psi front/27.5psi rear. I will probably set to 30-30.5 front and 27psi rear for the next time, should work good.
Last edited by longdaddy : 06-07-2006 at 09:53 AM.
i had very similar experience on michelin ps2 yesterday (first time at the track with this tire) - set the cold pressures same as I used to put in f1 supercars (36 front/34 rear, cold) and it was drift city after second lap! VERY SCARY. I kept taking the air out, eventually settled where the car would behave MUCH better, but I still had to cool down every 20 minutes as rear would get swingy in the middle of the turn. I am going to check cold pressures today to see what I finally settled on. Next time I go i would probably take out another .5 psi out.
The good news is that thread surface and outside edges were in MUCH better shape compared to goodyears exposed to the same track. It might also have something to do with the design of the surface, michelins have much more "rounded" edges.
Bottom line - if you track on ps2s, watch your pressures carefully and don't go in too deep in the first few laps - these tires can definitely surprise you.
UPDATE: the "final" cold pressures were 31psi front/27.5psi rear. I will probably set to 30-30.5 front and 27psi rear for the next time, should work good.
longdaddy. What was the ambient temperature at the track you were at? The reason I'm asking is that the temp at Thunderhill was about 90 degrees give or take.. The 25 psi (stone cold) seemed to be good, but I was definitely going to reduce the pressure in the front tires to see if it helped with understeer. I'm surprised that 31 and 27.5 psi cold worked for you.
ambient was maybe 70 tops, there was some cloud cover near the end of the day too. I could have dropped more pressure but I was a little paranoid about wearing out the edges/outside thread. Besides, i'm slow so the understeer was not a big problem, it was the rear swinging out that concerned me the most.
I'm going to be at thunderhill at the end of july, so I am definitely going to try even less pressure.
I don't understand why the Micheelin PS2's are so highly rated over the Goodyear F1 supercars on TheTire Rack's website.
I have had 2 Z06's (F1 SuperCars) and an 05' S4 (came stock with PS'2)
IMO, the Eagle F1 Supercar is the best DRY, NON-RACE tire out there.
The PS2's are one of the best for YEAR-ROUND performance and way better in the wet than the F1 Supercars (maybe that explains the higher ratings on Tire rack), but IMO they do NOT hold a candle to the F1 Supercars on dry pavement.
If you look at the Z06 and the Ford GT (both use Supercars as OEM) they have some of the top lateral g's STOCK (both over 1.0g) over other ultra high performance cars.
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so the understeer was not a big problem, it was the rear swinging out that concerned me the most.
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