I want to get 17' rims at some point in the future. I want the looks but without sacraficing too much speed. I got new tires put on when I bought the car that fit the 15' GLE rims and they should last a while . If I want to get 17's do I have to get new tires also or is there a way to use my current tires?

 

No, you have to get 17" tires fpr the 17" rims.