are 1.08 inches larger in diameter or 1/2 inch taller than the 35s. You are correct about the rears being smaller. The sidewall on a 245/40/18 is 98mm while a 275/35/18 has a sidewall of 96.25. Only a 1.75mm difference but indeed a bit smaller, and it shows. Like the appearance of you 275/40s...