@RevNev … have to ask, how much test/try/scrape/new/test/repeat did you go through to get to here?
The wheel thing started early 2017 with my old GenF R8 and a set of Simmons FRC's with the OEM 255/35 and 275/35 tyres. Front wheels were 20x8.5 ET35, rear's 20x10 ET45 and I thought 255's are too wide for an 8.5" wheel and the taller (HSV fitment) 275/35 I couldn't stop scraping on the rear of the guard. Ideally, the front and rear tyres need to be the same diameter and to achieve that, you need a 245/35 and 285/30 or a 255/30 and 295/35. A 255 needs a 9" wheel preferably but there's virtually nothing you can buy readily in Australia with the right widths and offsets with Brembo or AP caliper clearance. How I got onto the Forgestar wheels was seeing a photo of a Chev SS (VF Commodore) in the USA with 305/30's on the rear. I emailed Forgestar who knew more about Chev SS and Pontiac G8 fitments than any wheel supplier I'd spoken with here In Australia and they had the wheel width and offset range to suit with various dish profiles and you can buy off them directly and they'd send them to Australia.
The first set of Forgestar CF5's I bought were 20x9 ET38 and 20x10.5 ET52 as they recommended with 255/35 and 295/30 tyres. They fitted perfectly scrape free on the rear with 6mm trimmed off the guard lip. I don't like rolling VE/VF Ute guards as they tend to kink in the centre where two panels join and trimming the lip on the edge of the spotwelds flush with the guard liner I think is a safer and more tidy option.
I had the idea after carefully measuring what I had, that I could go wider in the wheel and with a 9.5" front, I could get a dish profile matching the rear as the 9's were a bit flat and lacked concave. The issue was caliper and spoke clearance with more concave on the 9.5" ET38 front wheel and from Forgestar's engineering drawing and the caliper measurements I provided, it' seemed I'd have 4 to 6mm clearance. I took a punt and bought a set of 20x11 same off set ET52 and 20x9.5 front same offset ET38 and fitted the same Bridgestone S007A's I had on the previous set. It all came about when a mate of mine wanted a set for his Gen F GTS, and with proven fitment he could visually see, he bought the first set of Forgestar's straight off my Ute.
I could "just fit" a 305/30 on the rear with a 10.5" if I cut a piece of the inner guard lining away but they looked too wide for a 10.5 and won't fit with 11" wheel. The 255 on a 9.5 and 295 on an 11" is probably the ideal size for maxing out wheel width without the tyre looking stretched.
Here's a photo from the rear showing how far out they protrude, still within the guards to avoid scraping.
