I need more traction: will these rims fit my fc without excessive rubbing
 

17x8 +35 with 235/40 tires
17x10 +35 with 285/?? tires

I have JIC coilovers with an inch or so less than stock ride height.

I need more traction than the 17x9 245 tires I have offer.

no ideas on rear, but front 17x8 +35 you should have no major issues

NO FREAKING WAY can you fit 285's on the back, im pretty sure 255's are the pushing limit and even then ive heard of some ppl not likeing it or having clearence issues. I personally would go with 245's on the back and 235's up front. Im sure you can make any tire WORK if you used spacers and had the right offset rims, but, i hope you dont care how it looks/ have a REALLY wide body kit

How much power are you making?

James

400+ hp at the wheels. Any way a 275 tire would work?

I had 265's on a 9.5in rim with +40 offset and I had no rubbing at all. You might be able to get away with the 10's if you change the offset.

Using drag radials or street tires?

i would recommend to get different tires and chage the spring rate on your coilovers to meet your needs before i change rims