I was reading that it's possible to have 245/40/18 tires on 18 x 7.5 wheels on a 4th generation without problems. Right now I have 225's on my maxima and I was wondering if the 245's are going to ride smoother than the 225's?

 

I guess that you could....but why? I'm pretty sure the ride would be a bit less harsh, but it would look like balloons on your car. I think you could probably get away with a 235/40/18 on a 7.5" rim, but a 245/40/18 is kinda large! If you're going for more comfort, look into a 235/45/18, but options are very limited in that size. There are tons or options in a 235/40/18.

 

BRAN808 .... would the 235/45/18 cause any diameter problems in my car?

 

look at the tire calculators...