B Stead

Well, I am a wheel and tire fitment developer.

Here are the updated fitments for the C8:

Front, 255/40-18 on a 18 x 9 46mm to 50mm wheel with a 50mm wheel found in the Enkei GTC01RR and a preferred tire found in the Eagle F1 Supercar 3
Front, 255/35-19 on a 19 x 9 46mm to 50mm wheel with a 48mm wheel found in the BBS CI-R and a preferred tire found in the Pilot Sport Cup 2
Front, 265/35-19 on a 19 x 9.5 52mm to 53mm wheel with inside clearance not yet confirmed but with a preferred tire found in the Eagle F1 Supercar 3 & _PSC 2

Rear, 325/30-19 on a 19 x 11.5 62mm to 63mm wheel with a preferred tire found in the Eagle F1 Supercar 3
Rear, 325/30-20 on a 20 x 11.5 62mm to 63mm wheel with inside clearance not yet confirmed but with a preferred tire found in the Pilot Sport Cup 2

Well, the 325/30-19 rear tire might be paired with a 275/35-18 front tire ! But check the front brake clearance and the suspension arm clearance.

Now I wouldn't recommend front/rear 265/325 tire sizes on a C8 lowered one-inch on stock springs.

Or there is a "put something on quick" setup as:

Front, 255/35-19 on a 19 x 9 48mm BBS CI-R wheel with a preferred tire found in the Pilot Sport Cup 2
Rear, 315/30-20 on the 20 x 11 64mm OEM wheel with a 5mm spacer and with a preferred tire found in the Pilot Sport Cup 2 but actually branded for _another car

Also note that the wheel offsets for the Ultraleggera wheels are not yet known.

But here is a link for correctly confirming the fitments with measurements for each individual setup:

http://www.kbhscape.com/wheel.htm

Well, wheel-width inputs can be used to measure wheel clearance over suspension arms while tire section-width inputs can be used to measure inside and outside tire clearance
.