I got some 1986 IROC rims for my 86 Camaro. I've heard that 315/50/16 will fit but will be taller. Also I've heard that 295/50/16 is the widest that will safely go on a 8" rim.
I'm only talking rear here, my fronts will be 255/50/16.
I don't want the rear sticking outside the fender though.

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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Trick Flow Heads, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine belt setup, Dual IROC Fans.

http://www.sethirdgen.org/octride.htm

 

I found the answer here: http://www.devek.net/wheelfaq.htm

quote:
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How does the ratio of rim width to tire width affect performance?
Of utmost importance is matching the rim width to the tire section width. A wheel to tire ratio of .88 to 1.0 is desirable for predictable wheel/tire performance and sidewall behavior. Too wide a tire on too narrow a wheel, for example a 275 on a 9" wheel, yields a ratio of .83 which will produce unpredictable sidewall behavior. On the following pages you will see our recommended tire sizes based on this ratio as well as other factors for each wheelset. Other tire fitments are at your own risk.
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So on a 8" rim a 235mm tire yeilds a aspect ratio of .86 which is closest to the recommended .88



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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Trick Flow Heads, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine belt setup, Dual IROC Fans.

http://www.sethirdgen.org/octride.htm

 

Hey John I am running 16x8(ROH the same ones that came on the FireHawk & Impala SS) all around with B.F. Goodrich 245/50-16 radial T/A's and have had no problems for better then 28,000 miles. When I get my car done I will go with a 265/50 out back and stay with a 245/50 up fornt.

 

The quote states that the recommended aspect ratio is between .88 and 1.00. .86 is not the most desirable ratio, because it does not fall within that range. 235s look too skinny on 8" wheels. 245s are the most desirable size -- 255s have a slightly wider footprint, but have more ugly sidewall and, of course, more sidewall flex.