We kinda had this topic aready, except, I want to be sure to be with the right aspect ratio so my speedo is correct when I get new tires this time. Last time I got 205/60/14's for my wheels, I clearly saw they were taller then the stock wheels/tires when put next to each other. I used the chassis dyno and showed about 74mph when my speedo showed only 70mph. So obviously when I went past 120, it was probably closer to ~130mph.

I'm forgetting whats the right Aspect ratio WOULD be. never mind the width of the rubber actually. I'm running 205's on my '85 for 4years no rubbing for your information, but did bottom out a couple times and one of the bump stops for the rear springs had fell off and caused some unwanted lipping.

Is ???/60/13's correct? Is that what stock is right?

Then, 205/50/14's for 14' wheels.

Now, if you go to a 15" wheel, you'd be using 205/40/15's then correct.

And...205/30/16's for 16" wheels then?

 

Stock for '85 GS, GSL was 185 70R 13. Stock for SE was 205 60R 14.

 

There are slight differences between tires with the same published specification. Your best bet is go to the web site of your prefered maker tire, such as Yokahama, and it gives you the actual radius for each model and size. For example with 14" its the same for their 205-60 as 195-65.