Hey, I am looking at buying tires/rims for 04 civic. I found a good deal for 17 inch rims. 2 of the tires are 205/40/17 and the other 2 are 205/50/17. I know I would put the bigger tires on the back, but is there any reason not to do this? Does it look better/worse? thanks a lot

 

A DX should have 205/45/17s and an EX, 215/45/17.
You should NOT use different diameter tires in the back or anywhere. It is possible to have wider tires in the front or back if there is no interference with suspension components at full shock travel AND both sets are the same diameter.

The other thing you have to look out for is the offset. I wouldn't venture beyond 38-42mm.