I currently have Dunlop SP Sport FM901 215/35 on my rear 18x8.5 wheels.

The reason that i have the 215's on there is because i used to be on air and with the rear all the way down, having these tires with a slight stretch would eliminate rubbing or having the fender cut into my tires:


So what would be a good tire size to run?


My current rear tires (over 25k miles on these):

 

S-chassis guys usually run 225s or 235s for 18x8.5 wheels

but i think the reccomended width on 18x8.5's is 245mm

 

From what i've found 255 is standard if you're not going to have any clearance issues. I'm thinking more toward 235 or 245 though (something is rubbing back there which doesn't make sense cause when i was on air i didn't have any rubbing but now with 2 people in the back or a lot of stuff, going over a bad bump will cause both sides to rub and i think it's the top of the tires rubbing the top of the wheel wells )

so maybe the springs compress more than the bags did since the bags had stops inside them, but oh well

 

Nitto has a good refernece tool:

Nitto Tire - High Performance Tires for Car and Truck Enthusiasts

they show a 235 or 245 as ideal for an 8.5in rim.

 

255 would fit fine as well, but thats pretty a bit much for your car unless it does fit

 

^^ thanks for the link and info

 

I run a 225-40-18 on my 18x8.5. It's stretched and the ride is a little too rough.
I would like more sidewall so i will probably run a 235-45-18 next time I buy tires.

 

yea mine's a little too rough as well, but i don't think i could run 40 series, i'm already having the top of my tire on the passenger side rub the top of the wheel-well when i have people or a lot of stuff in the back of the car.