Mikii

I have MB E 350 2012, all tires are 245/40R18 Dunlop (50% used) . I want to use only new tires on front 225/45/R18 Hankook and keep the old one on the back. What is the downside/upside and what is the best to do?
I'm looking for advice, please anyone with knowledge on the subject to help me.
Thanks up front.

Yidney

First, you can post in the E forum, since this is the CLK forum. Second, before you post there, I suggest you make your post make sense.

tw2

Why don't you run the whatever the recommended size is and leave it at that? If they still have life left why are you wanting to replace them at all? Any why only two of the four tires?