Autocross tire size for a heavier car

I just picked up a 3.6L '06 CTS with a 6spd so that my wife will autocross with me. (she said my turbo Opel GT is too barbaric) I'm looking at two tire options 235/45-17 or 245/45-17. Wheel width is 8". The question is would I be better off with the wider rubber or would the 245/45 be too sloppy on an 8" wheel?

I autocross a big girl too My Subaru SVX when fully dressed was over 3,500 lbs. I use 245/40-17 in 17x8" wheels and they fit and work well. Unless there is a compelling reason to use the 235's (major sale, solid hand-me-downs, brand you want not offered in 245, etc) I say go wide.

315.

Just because.

I autocross muscle cars on 255 or 275. But I suck, so I really have nothing relevant to add to the conversation.

Needs to keep stock wheel width to stay in FS, thus the 8" wheel requirement. I agree 245's. A 3.6L CTS can be surprisingly competitive in that class.

I autocross a 2012 Honda Accord sedan. No real science behind it, but I use 18x8.5 Enkei wheels with 235 front RS-3 and 225 rear RS-3.

Thanks for the responses. It looks like my stock wheels are actually 17x7.5" and there was an 18x8" optional wheel. So, to stay in FS class I would have to run the factory 17x7.5" wheels? According to the tire specs 7.5" is the minimum approved wheel width for both the 235 and 245 tires.

I'd like some info your turbo Opel GT.

1971 california car. Nissan SR20DET red top w/5spd trans running 10psi boost, aftermarket manifolds,FMIC, honda civic aluminum radiator, chipped ecu w/launch control, Avid AV-6 17x8 wheels, Maxxis MA-Z1 tires, Volvo 4 piston front brakes with vented rotors, adjustable fiberglass front spring, Koni shocks, front&rear swaybars, OGTS poly front bushings, Z31 300zx drive shaft, Volvo 240 rear axle (3.73 ratio with auto locking diff), adjustable pan hard rod, custom torque arm with F-body front mount, diy polyethylene front air dam, custom side skirts, acura integra seats. It weighs about 2100 lbs.

If the 18x8" was available as a standalone option, you can legally run the 18x8". If it was part of an option package, you have to install everything that was part of that package in order to run the 18x8". Street rules would also allow you to run a 17x8 or a 19x8 (but you probably wouldn't want to run a 19x8).