In the early 80's I was running to as far as I can remember these tires in the back in my 66 GS on Keystone 15 inch rims. I remember if they 10 inch wide rims. I bought them from a friend who had them on the "front" of a whack out modded 65 GTO I did have to put 2 to 3 inch springs in the back for clearance. My mind tells me they were N50's and I know they were a low profile tire and measuring the total diameter I had to mentaly adjust the true speedo reading as they were a bit shorter than the stock 7.75 x 14 I had to basicly raise the back as the rim width was bringing the tire out to just about under the wheel well.. Iv'e googled for 2 days for vintage Firestone tire info in the N50 sizes and can't find anything..Only thing i'm finding in these sizes is MxH drag tires or Coker repro's that are a bit taller than stock. Doe's anyone have any idea's to where I can find anything at all?
I know they aren't Firestones but Mickey Thompson still makes the Indy Profile SS's... https://www.summitracing.com/parts/mtt-7076 Well crap! I just looked at the Summit page and it says "not available" If they are not available, take them off the website!
Here is a tire chart listing all the Letter tire sizes. So the N50-15 Bias ply tire went on a 9" rim, and had a 12.65" section width with a 27.50 overall height. So 12.65" is 321mm. The closest size would be a P325/50R-15, they are 27.8" tall. Phil Sedlon (70 gsconvt) runs them on his 70 GS. http://www.v8buick.com/index.php?threads/biggest-wheel-tire-on-a-70-gs.116230/#post-893895
