I have heard they put 18"'s on the front and 19's on the back on Benz race cars, but I was lucky enough to have checked out a racing CLK at a dealer and found that both wheels were 18's. However, I think that would be cool and very exciting to seen 18's on the front and 19's on the rear. I have always wanted to do that to my CLK. Instead I have 19's all around. OObenz