So tomorrow I am gonna go for 285R 255F but I still have a few question.

1. How much of an affect does this have on acceleration?

2. Do these tires affect gas mileage much?

 

I have those sizes on 20". If you are putting the on 20" wheels, the wheel diameter will negatively affect the acceleration more than wider tires. I still get great mileage, better than most people have reported but I drive mostly highway. I haven't noticed that it's worse since getting 20s but it probably is just a very little bit. Physics says so. But not noticeable for me.

 

No I am putting them on stock 19' rims i got with my G37S

 

I don't think you'll get any noticeable loss of acceleration or mileage.

 

loss of acceleration? I was hoping wider tires improve accleration considering the amount of traction from wider tires

 

Are you on stock suspension?

 

ever single thing is stock

 

Ok, I was going to say you may have to trim the felt wheel well lining and bumper bracket, but you should be fine at stock height. Wider tires will increase traction and increase better cornering.

 

You'll feel imperfections and ruts in the road more, it will wander more easily when the road surface is uneven. Somewhat more suceprible to hydroplaning too.

 

Why? I thought wider tires up to like 275 or 285 would improve traction and stuff. Why would performance vehicle generaly have wider tires if this was not te case

 

With a wider tire, more of your "car" is touching the road, thus you feel more imperfections and "wandering". As far as hydroplaning, I can only hazard a guess. I'm gonna say that with more tire on the ground, it's harder to get water underneath the tire out (if that makes sense) and thus you're more susceptible to hydroplaning.

 

I decided to go with Hankook Ventus V12, 275R and 245F... 285 were probly to much and from what I have been hearing that wide can reduce performance

 

ah man... I was hoping to see 255 and 285s...