I am autocrossing just about every weekend with my GT3 RS/PCCBs and want to go to Hoosier A series on 18s for a better selection of tires. Any wheel/tire reccomended combinations? Would the same wheel/tires also fit on my 997 C2S?

 

Sorry. I wasn't trying to be condescending. I misunderstood you. I have almost no experience with true slicks on a big heavy car. (My slick experience has been racing formula mazdas which are fastest when driven at fairly big slip angles.) Real race cars don't have fenders

I'm picking up my GT3RS friday, so I'll be in the market for some 18" track wheels and tires shortly. How much camber do you have to run to keep the true slicks happy? I don't want to have to do an alignment change before every track day. I plan to live with a couple degrees on the street to let the r-compounds work on the track. If a true slick could live at that camber, I might just try a set instead of the hoosiers. A compromise alignment on a slick might still perform better than an R-compound??

 

I agree that "real" race cars don't have fenders. But, I'm still playing around with these silly Porsches that have fenders bash in when you dive bomb a corner rather than catching on someone else's wheel and launching you and the car into the air. I know, I'm a chickensh*t.

No offense taken at all. You're right, the cars are heavy, since I don't have any experience in a lightweight car, I wonder if that is where the difference in how the tires cut loose at the limit? I can see that with my heavy Supercharged 996, the tires would progressively let you know that they are about to expose you to some amount of "pucker factor;" whereas, the lightweight open wheel Formula Mazda is gripping one second and spinning the next. With this in mind, I suppose I misunderstood you too.

Wow, I'm jealous of your GT3RS. I have a 1999 EVOMS Supercharged 996, which Global Motorsports Group (GMG) has sorted for me. I basically have GMG's Stage 3 Suspension kit, which runs 2-way Motons, Eibach ERS mains @ 800 lbs. front and 950 lbs. rear plus tender springs. I have the adjustable GT3 anti-sway bars front and rear, dog bones, lower control arms, adjustable solid mount bushings, etc., etc.

My setup is awesome and I can't believe the car will handle like it does. GMG did an excellent job getting the right suspension under it.

As to your question re: how much negative camber? Like I said, I run the Michelin Porsche Cup (not Pilot Sport Cups) tires on 18 inch wheels, and with Neg. 4.2 camber up front and Neg. 3.7 rear they seem to do just fine. I'm still playing with my settings as I learn this new suspension and depending on the course I will be running. I think both the Michelin and the Hoosier could live and still work okay with less camber, say maybe up to 1.0 less. I would be interested in knowing what "compromise" settings you go with and how those work for you, so please keep us posted.

As to the earlier question of what wheels are good, GMG has some excellent (read lightweight and durable) HRE GMG Cup wheels. I am still trying to save up for a set, since I just blew all my play money on the suspension upgrades. You see, I'm a poor man on this board, but I do what I can.

I have started autocrossing this year too, and I've found auto-xing to be insanely different (relatively speaking) from road coursing. I don't know that my suspension setup is the greatest for auto-x and changing the setup to optimize it for each type of driving is too much of a PITA, so I just leave it setup for road coursing and suffer through the auto-x.

FYI, at the Mid-Ohio race in the GT3 Cup Series, the tech specs allowed the teams to go up to Neg. 4.5 and Neg. 4.0, but I don't know how much everyone was running. Well, I know what one team was running, but I can't disclose those numbers.

Also, FYI, another crazy difference between the DOT Hoosier R6 and the Michelin Porsche Cup tires is the crazy difference in tire pressures and expansion rates (even with nitrogen). Hoosiers definitely like a higher operating pressure.

 

As a side note, we recently put a set of our standard 19" C-20's on a local customer's GT3RS in 8.5" and 12" widths. He essentially wanted a factory setup. We did this at our facility, so we were able to weigh the factory wheels as they came off, and the HRE C-20's as they went on (we simply swapped the tires over). The HRE's were 4 pounds lighter PER CORNER in the front, and 7 pounds lighter PER CORNER in the rear!!! This totaled 22lbs of unsprung weight!

It is amazing how significant this was on a car that is so weight conscious.

Chad