8.5 is fine, but not at a +48mm offset. To get a wheel wider than 8" (really 7.5") you need a LOWER than stock offset. An 8" wheel should be in the low 30's for best fit, an 8.5" wide rim would be in the low 20's, and a 9" wide rim would need to be somewhere around a +10mm offset to work well.
If 235's are rubbing, you probably have bigger wheels or the wrong sidewall height. 235/40/17 shouldn't rub.
A 245/45/ is just plain way off - waaay too tall, WILL rub. Unless that's a 245/45/SIXTEEN, whioch is a nearly perfect fit, lol.
A 245/40/17 is a good fit, may rub on a lowered car a tiny bit.
Try to go wider and rubbing could be an issue even on a stock height car. 245's fit fine on an 8" rim, so while an 8.5 or 9 would be better in some small way, it's really not worth trying to find that crazy offset since 17x8's are readily avilable.
What class are you autocrossing in? If you're running DOT R-compounds, you're most likely either in SM or SMF, in which case go with the 17x8's - or Stock, in which case you are limited to a 17x7 inch wheel, period, and to offsets between +48 and +36. I have run on 245/40/17 hossiers on the stock rims for quite some time, and Ionick05 has my old stock rims with 245/40/17 Hoosiers on them now. I have Motegi's in a 17x7 forGS this year, with 245/40/17 BFG R1's.
A 245/40/17 is as much rubber as is going to go under there without a widebody kit, lol.
Originally Posted by AlphaJaguar5
I try and get with as many dudes as possible when I'm out on the road.
Originally Posted by h4ckler
I miss the days when people weren't emo and just hung themselves instead of bitching on youtube....
RIP "Sally" - Pacific Blue 2005 Ion Redline Comp Pack
14.8 @ 96 mph, 2.3 second 60' - 100% stock on stock tires, 85 degrees out at 2200 ft altitude...
207 whp, 187 wtq, 100% stock uncorrected
numbers on a mustang dyno...