[78w72]

always thought tire size numbers worked like this. the first number is the width of the tread in millimeters, so a 245 is 245mm wide. then the next number is the ratio of the sidewall based on that millimeter number, so a 60 series is 60% of 245 sidewall.

if thats correct, a 245/60 is only 30mm wider, which is 1.182inches wider than a 215/70... not 2" & not 3/4". but the 215/70 has a taller sidewall based on 70% of 215 vs 60% of 245. right? or wrong?

either way, a 215/70 may "drive" better for road feel etc, but a wider 245/60 will "handle/perform" better being its wider & less sidewall.

[David Jones]

Originally Posted by 78w72

always thought tire size numbers worked like this. the first number is the width of the tread in millimeters, so a 245 is 245mm wide. then the next number is the ratio of the sidewall based on that millimeter number, so a 60 series is 60% of 245 sidewall.

if thats correct, a 245/60 is only 30mm wider, which is 1.182inches wider than a 215/70... not 2" & not 3/4". but the 215/70 has a taller sidewall based on 70% of 215 vs 60% of 245. right? or wrong?

either way, a 215/70 may "drive" better for road feel etc, but a wider 245/60 will "handle/perform" better being its wider & less sidewall.

I cheated. I looked up what BF Goodrich said the widths are.
I do believe your calculations are correct in theory though.