205/40/18 - 82MM Sidewall
215/35/18 - 75.25MM Sidewall
You have 7MM Difference all around, that's over a 1/4" of difference in sidewall.
Technically, I think it's actually 14MM, because you have it at the "Top" and the "Bottom", which is more than 1/2" of Sidewall.
:wink: