yo. i have 17 inch rims and the tires on them are 205/40r17 whats the widest i can go on them like 215? my tires in the front blew so i wanna get them wider. the rims are 7" wide if that makes any diff. thanks

 

I used to have a car with 17x7s and I'm pretty sure I had 215/40s.

 

and whats the difference between 215/40 R 17 and 215/40 ZR 17? thanks

 

I would call Tire Kingdom (open Sunday?) and ask what is the widest tire that will generallly go onto a 7" wide rim...........that's a ballpark number, since different manufacturers have a slight variance in their measurements....regardless of what they will claim.
I have noticed that expensive tires will generally have a lower profile
than the same "sidewall-size" of a different, cheaper manufacturer.

Next choice would be to go to www.tirerack.com, and read up on their
width suggestions. Good luck, and let us know what you decided.-Bob