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Hi experts. I have a set of 18x8 ET 57 offset from a Cayenne that I was thinking to use on my 968 track car. I know people using 18s on their 944 Turbos, but I think they are staggered. To note, I'm used to a square setup with my current 17 inch wheels. Would these 18 inch wheels fit? The bolt pattern seems to be the same, but the wheel's center hole is a tiny bit too small to fit comfortably over the center guides. I'm really surprised that Porsche would change just that dimension for the SUVs. These are real Porsche wheels, not aftermarket. As for tire size, I think 255/35R18 would be needed. I'm currently using 275/40R17, which work well - they are a tight fit in the wells, but they don't rub anywhere. Some have suggested (including the prior owner) that 255 would be faster and better handling than the 275, I think because they would be lighter weight.
FYI - Suspension is full monoball, polybronze bushings, 800#/600# springs, Bilstein coilovers, M030 Sways, tower and lower support bars, etc.
My tire of preference is the Nitto NT-01, which is not made in 255/35R18, which is another complication for me.
I would love to hear your comments and ideas of how to best use these wheels and about tire sizing. That might include selling the wheels and using the $ to buy tires!
Wheel fitment is probably the most-asked question in all of Rennlist, and the situation can get pretty complicated, depending on your goals. You're doing the right thing by trying to keep your overall wheel diameter as close as possible to the stock 25". However, 8" is a very narrow wheel for a track application. How wide are your current 17's? I'm really biased here, but I think 17" is the optimum wheel diameter for our cars. A larger diameter wheel only adds weight. Also, 255 is WAY too wide of a tire for an 8" wide wheel. I wouldn't go any wider than a 205, 225 tops. I'm running 275/35-17 Maxxis RC1's on my 17 x 10.5" wheels in a square set-up. There's a lot of folklore and mythology surrounding the optimal wheel/tire width relationship. If you can get your hands on the December 2013 issue of Grassroots Motorsports magazine, read through the tire test in that issue. They tried several wheel/tire width combinations, and came to the conclusion that beyond a certain point, adding a wider tire on a given wheel accomplishes nothing - it just creates a bunch of sidewall flex. So, personally, I would pass on these wheels, and see if you can get your hands on a set of 17 x 9" Twists. They're cheap, although finding four in that size may take some searching and patience. Good luck.
Last edited by Cloud9...68; 03-21-2019 at 08:50 PM.
That all makes sense. I have a set of 17x9.5 wheels that I use 275/40R17 Nitto NT01 on those. The prior owner said to go to 255/40R17, but didn't really explain why. Maybe your idea of wheel width or tire width is the reason.
lol - definitely not my idea - I'm simply a convert to the wheel-width-is-what-really-matters religion, based on research and personal experience. A 275/40R17 tire is pretty large, at 25.6" in diameter, which will numerically slightly lower your axle ratio, which will cost you precious revs coming out of the corners, and it's really too wide for a 9.5" wheel, as its section width is over 3 cm wider than the wheel width. I'm running 275/35-17 Maxxis RC1's on my 10.5" wheels. I agree with the previous owner that a 255/40-17 would be a better choice.
03-21-2019, 09:01 AM
Wheel fitment question - 18s from a Cayenne
