QUOTE (ShoopraLazor @ May 26 2018, 12:23 AM)
Just because they came that way from the factory doesn't mean that is the fastest setup. Plenty of ST competitors running 205's on 8" wheels and 225's on 9" wheels.
Yeah, pretty much my rational. Never understood why GM spec'd a 275 on a 9" wheel when everyone else "usually" runs 245s or 255s for 9" wheels. I've always felt like a 9" wheel would usually be too narrow for a 275. Maybe for the drag racing crowd that wanted a wide tire?
Falken says you can run a 9-11" wheel on them, figure the wider wheel will give more grip (slightly larger contact patch from being a little stretched + less sidewall/tire flex). But hey if someone has 17 or 18x10s or wider I'll take it.
I think you're the first person to say they run a Fbody in ST (or have even seen that).
My opinion is that you match the tire width to the rim size. You certainly don't want to run tires with the "stretched" look to them like some slammed-tuner-camber cars have, that's just dangerous. Plus we should also acknowledge that different tires have different actual tread widths- a 245 from Kumho may have more contact patch than a 245 from Bridgestone. FWIW, my 9"/275s look "square" on the rim, ie matching the rim width almost exactly, the sidewalls don't bulge in or out dramatically.
High HP cars are, by definition, under-tired. The 93-97 had 8" rims and 245s IIRC, which was too little tire for a heavy car (I had that until I got 9"/275s). For AX, there's a sweet spot for weight vs tire, IMO. I'd bet $1000 that the same Fbody on 315 street tires is faster than on 245s at AX. Unless maybe your AX course is a tiny postage stamp that doesn't allow for big fast turns.
If your local class is small or budget doesn't allow for 315s, I understand, but my recommendation is always go wider.