You bring up many good points and I will try to address a few of them here. First, at Finspeed, each set is made to order based upon what the customer wants and their intended purpose. Some companies will premachine a wheel, set it on the shelf, and then when they receive an order, they do a final "cut" to make it fit the application; be it a GTR, GT3, Corvette or whatever. We don't do that. Every set we make is made to order. Back to your thoughts: Obviously, there are constraints that limit what can be done given the location of suspension hardware, suspension mounts, brake hardware, etc. We actually 3D scan those applications where the owners want to get super aggressive or creative. In fact, we just finished a scan of a Senna so will know exactly the limits of what can be done with respect to wheels. We have scanned my 570S and while the brakes and suspension are from the 720 on the 600LT, most of the limits for the wheels remain the same. For my track set up, we went with 19x9s in front and 19x11s in the rear as I want more tire options; the 19s in the rear allow that. So, I went 1 inch wider both front and back with no issue. We can offer some suggestions if you want to go wider or different off-sets. Second, for Geoff2010's setup, he wanted to maintain the option of using stock Trofeo Rs so he will be getting 19x8.5 fronts and 20x11s in the rear. The 8.5 inch width up front will allow Trofeo Rs plus other tires that make a 235 section to help with some of the understeer. He did not have the desire to go wider in the rear. I will confess that I am not sure a wider tire is really necessary in the rear having driven the 600LT; it seemed to hook up well and bigger/wider is also heavier (all things considered). I would not discourage you from going wider if you want to though as I applaud being aggressive! Having said that, you are correct in that you can go wider in the rear. How much more? We would have to do some modeling work to be sure but can figure that out if you or the rest of the forum are interested.
You are also correct in that some tires of the same size have different heights/diameters so again, that goes into our modeling to make sure there are no computer issues. It all comes back to Finspeed wheels being bespoke and understanding how the customer will be using them and knowing the other factors that come into affect. Not only will we help assist with the proper wheel for you, but we will also recommend the proper tire(s) to make sure everything works in harmony.
I hope this helps.
PS: I am not quite sure what you meant in your penultimate paragraph with the discussion of the 235 section and then following that with "However, both PUR and Finspeed still are still using 11s in the rear." Could you please restate and I will respond accordingly.
Last edited by Kfehling; 03-19-2019 at 03:51 AM.