audi a4 tire downgrade - Audi

hi everyone,

do you think it is ok to downgrade the tire size

from 235/45/17 to 215/40/17 on my audi a4 3.0?

all i want is try to improve little fuel ecemony

and lower couple centimeters on the car body height?

thanks

--
http://planestrain.myphotoalbum.com/albums.php

--