I have four sets of RPF1s and need to decide which ones to sell or keep.
17x9.5
18x9.5
18x10.5 (x2)

I like the idea of faster acceleration with the 17s and it's about $20 cheaper per tire versus 18s. Cont Extreme Contact Force is avail in 255/40 and 275/40. Suggestions? I know plenty of other tires are available but these a lot of them are back ordered. Btw, this car is street/track. I was planning a dedicated track car but changed plans.

I've run square 275/35 NT01s on the 10.5s and wasn't crazy about the steering, which seemed to me to counter the additional grip. I was thinking going square 255s on the 9.5s. or doing a staggered 255/9.5 F, 275/10.5 R.

I've run 245/40 F, 255/40 R on the oem 18x8s and it felt really good with VDC off. I think I'm leaning towards leaving VDC on though going forward. in my garage is full of wheels and tires!! so I need to get rid of some.

 

I would go with the 18s. Especially if this is a street/track car, 18s just look better. In terms of handling you also should consider that technically an 18 of the same width has slighly more contact surface than a 17, although this is minimal. That being said, this has been a part of the argument for why a lot of high performance cars are now running even 20s.

I've tried a staggered 255F,285R on track for one season and it was a very poor experience. Waaaay too much understeer. I swapped to 265F,275R on 19x9.5 F , 19x10 R rims and have never looked back. Still run the same tire size and rim setup for 5 years or so now. This platform just really likes square or nearly square setups.

 

thanks for the advice.
I'm leaning toward keeping one square set of the 18x9.5s and then using slightly larger rear tires per your suggestion.
I'll sell the 10.5s and the 17s.
I just bought an older Cayman S which came with drag strip stagger: 235/295 on 19x8.5/11. Understeer was really bad at the track. Totally different car that works better with some stagger, but not THAT much...

 

18s give you more room for large brakes, that's more important than any weight savings from smaller rims.

The suspension setup for square vs. staggered is quite different and if your car is setup for staggered and you switch to square setup it will behave badly. Once you adjust your suspension for a square setup you'll appreciate the extra tire in the front and the ability to rotate tires for better wear.

 

Ah. I was wondering if the Z handled better with slight stagger. I'll try it again on the next set of tires. thanks for the info!