[Lang]

Tony

Where abouts is the reference to that. I can't find it in the Tyre and Rim Association manual.

Not saying you are wrong but the manual says the difference between 7.50x16 and 7.50R16 is only 4mm overall height (within normal manufacturing leeway). Everything I can find says the old tyre is 100 aspect ratio making the "R" tyre the same.

Maybe some of the other sizes went with the 78%?

Of course that stand alone "R" measurement only applied to tyres in the transition period between bias and radial construction - you can still find a few sizes so marked being produced for older applications. I think the 8.25R16 is still in use with the little 3-5 ton Isuzus and Mitsubish/Hinos.

All tyres have "R" in the size now but it is preceded by the aspect ratio so has nothing to do with size eg 185/65R14

Lang

PS

I just measured the 8.25R16 tyres on my OKA. Exactly 8.25 wide and 8.25 high giving an aspect ratio of 100.

PPS

I went looking and found a 7.50R16 M&S pattern on a wheel. Measured exactly 7.50 X 7.50. Measured the 7.50X16 Military ND on my 1/2 ton Dodge - exactly 7.50 x 7.50