With a 17" OEM sized tire and wheel, if you can pass a #2 pencil between the tire and the strut the clearance is fine. If you cannot pass that pencil between the 2 then the strut is starting to migrate towards the tire.
There is like only 1/4" distance between the two. With the 18" the distance will be greater.
I thought the 17s are 17X8 with 245-45-17 and the 18s are 18/8 with 235-40-18. If the 18s distace is greater, it must only be due to the tire size then as I thought the rims were equally wide?
2003 Corvette Z06 - MGW shifter, Corsa X pipe, Corsa Xtreme exhaust, Texas Speed long tubes w/o cats, PowerStop rotors/pads, Conti DWS tires, C6Z51 F&R sways, C5R headlights, tuned
04 GTO - sold