What size rims came stock with a 91 camaro rs? i keep being told they are 15's but i think they may be 16's

Tire is ... 255/60R16 98h

 

R16 on the tire refers to a 16" rim size.

For more information hop over here:
https://www.thirdgen.org/1991-chevy-camaro

 

If your tire size has 16 in it than you have a 16" wheel The 91/92 Camaro RS came with the 15x7's or you could get the 16x8's like you have judging by your avitar pix. My 92 RS has the 15's. All 91/92 Z28's came with the 16x8's like you have. The 15's look nothing like your wheels. Below is a pix of my car with the 15's

 

15s were standard on the V6 cars, but you could option for 16s. All V8 cars came with 16s standard.

 

I know the Z28's only cam with the 16's, but did not know you could not get the 15's on a Lo3 car. I'm still learning form this site everyday.