Which is better for street driving, 17" or 18" and why?

I'm debating running 245/45-18's versus 245/45-17's. I want to run the same tires/rims front and rear. My goals are to reduce understeer, balance handling, and lighten the car.

Are 18's more popular now because they handle better, or because they look better?

 

18's look better. You will get a smoother ride with 17's. You should check the tire size's they should be different for 17's and 18's. Use a tire calcuator to make sure you get tires that are the same overall size as stock.

 

I think 18" is the balance of look and handle
you can still get good tire height and still not look like a 4x4

 

Big advantage with the 17's is the tires are cheaper so if you're looking to change the handling, you can go to the Falken Azenis Sports in 245/45R17. Any decent tire in 18" costs bucks. I went from stock 17's to Performance 18's (both with the RE040s) and there was a slight difference in ride quality, otherwise I like the 18's because they look better.