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This thread is a mile long, so excuse if this has been discussed before. To me, the 997-C4(s) wheels are a perfect fit and the 997-C2(S) wheels with a 17mm spacer as well. Both are readily available and cheap track wheels. Both don't have the disadvantage of sticking out beyond the stock measurements and hence no clearance issues.
Attached is a little tire/wheel calculator spreadsheet I have used for some years to gauge where the tire / wheel edges are relative to stock.
Look at the Xinner/Xouter measurements for tire and wheel. These should line up with stock measurements as best as possible.
For example, the CH-R wheels/tires in one of the recent posts results in 10-12mm too wide, which still seems to avoid rubbing. Play with it yourself.
You will find that some of the aftermarket wheels being pitched are way out of factory specs.
Good luck!
So dope thanks.
I just want a one stop shop to find out what is the widest and most offset I can get for the front/rear in 18".
Correct, it's brake clearance issues that are the culprit which is why for street-GT4's we recommend for track usage 19" fitments which we're getting closer to confirming and having photos of. I'll send over a quick message
Are you guys going to have 18" wheels (like you did for the Clubsport) that do clear non ceramic brakes in the GT4?
Are you guys going to have 18" wheels (like you did for the Clubsport) that do clear non ceramic brakes in the GT4?
Net of the long conversation is that it's impossible to run 18" wheels with OEM brake calipers on the front axle. There is not enough clearance to make a wheel that is safe for the track. Theoretically you could either move to a 997.2 GT3 caliper, which has a lower profile than the 991/981 caliper, and will work with the same size rotor, or swap out the whole system for stoptech.
Net of the long conversation is that it's impossible to run 18" wheels with OEM brake calipers on the front axle. There is not enough clearance to make a wheel that is safe for the track. Theoretically you could either move to a 997.2 GT3 caliper, which has a lower profile than the 991/981 caliper, and will work with the same size rotor, or swap out the whole system for stoptech.
Agreed. GAZZ emailed me again about 18s so I hung a 10" * 18" Forgeline with a 305/660/18 Pirelli PZero slick (rated at 305mm but really a 297mm section width and rated to work on a 10" - 11.5" wheel) and the rim clears the rear caliper but it's so tight in there. We have about 20mm of toe link clearance BUT it's tough to gauge quarter panel protrusion with the car on the lift. It's so tight in there as far as inner barrel clearance. Any pebble would scratch the rim of the caliper if it got wedged in there.
Up front we know the bolt spacing of the GT4 upright would accommodate the 997.2 GT3 brake caliper and therefore also barely fit.
It's just so tight. I know it all seems to clear and maybe work but i worry about clearance and things getting wedged in there on track. Not to mention, more clearance means more air circulating to cool things.
My long Phase I modification process will hopefully be done tomorrow and when the motor is in and I'm on the ground I can check this again for rear quarter panel clearance.
John, is it your opinion that 19" wheels will be the preferred size for this car? Between the need to change the front calipers, the minimal space between wheel and brakes for air flow, and the risk of getting debris lodged in there, 18" wheels are looking less and less desirable.
Last edited by Beantown Kman; 02-24-2016 at 09:59 AM.
Are you guys going to have 18" wheels (like you did for the Clubsport) that do clear non ceramic brakes in the GT4?
Originally Posted by ShakeNBake
Net of the long conversation is that it's impossible to run 18" wheels with OEM brake calipers on the front axle. There is not enough clearance to make a wheel that is safe for the track. Theoretically you could either move to a 997.2 GT3 caliper, which has a lower profile than the 991/981 caliper, and will work with the same size rotor, or swap out the whole system for stoptech.
If someone possibly upgraded to the Clubsport brake option it'll be more possible, but with PCCB's to answer the question, there's really no light at the end of the tunnel for that, I doubt there will be a solution for that. Since there are slicks available in 19" sizes, I think that should hopefully satisfy the majority of end users who are looking for a track set.
[QUOTE=HRE_Jurrian;13047136][FONT="Century Gothic"][SIZE="3"]If someone possibly upgraded to the Clubsport brake option it'll be more possible,
Up grading to the Club Sport brakes would be a very costly proposition.
Although I can sell the PFC replacement rotors and pads....the Calipers are only available from Porsche Motorsports. Think most are looking at going to the 997 GT3 Caliper.
[FONT="Century Gothic"][SIZE="3"]If someone possibly upgraded to the Clubsport brake option it'll be more possible,
Up grading to the Club Sport brakes would be a very costly proposition.
Although I can sell the PFC replacement rotors and pads....the Calipers are only available from Porsche Motorsports. Think most are looking at going to the 997 GT3 Caliper.
Originally Posted by Finspeed
We will be switching to an 18 and the 997 caliper on our shop GT4...when it shows up.
I wonder if the 996 GT3 calipers from my Cayman will fit!
The 996 GT3 Cup caliper fits the standard 981 front upright which I believe is 142mm but you need the larger spacing from the 997 GT3 caliper which I think is 210mm. I can measure tomorrow. I'm doing this package right now on the 2 981 race cars we are building.
02-23-2016, 11:44 PM
