Okay I know this has been beat to death but what is the widest tire we can mount on the stock wheel. I am asking because I would like to mount a good set of all season radials to offset the issues when driving my car in the snow.

http://www.tirerack.com/tires/Compare1.jsp?startIndex=0&width=255%2F&ratio=40&diameter=18&search=true&pagelen=20&pagenum=1&pagemark=1&performance=UHPAS&performance=HPAS&performance=PAS&performance=GTAS&performance=ST&performance=AS&x=15&y=12

I found that 255/40 WR18 is only .2% different than stock. The side wall is the same height just 30mm wider. The tires that came stock are just slightly narrower than the outer edge of the wheel. Will installing the wider tire interfere with suspension ect.

And what is the max percentage that we can deviate from stock without affecting the ECU ect.?


Thanks for your input into this!

I'll admit I don't know the answer to your question (and am curious my self, for my own reasons) but I just wanted to point out that you actually want to go to a smaller and narrower tire for use in snow, not wider.

Just for an example I checked Toyo's website for their Proxes FZ-4 all-season tire. It's one I've had good luck with in snow.

A 235 or 245 treadwidth calls for minimum rim width of 8". FWIW I have 245/45/16 tires on my 16x8 RX-7 rims with no probs.

A 255 treadwidth specifies minimum rim width of 8.5".

I've asked a similar question before

http://www.rx8club.com/showthread.php?s=&threadid=14783

Hope this helps