i am looking to get some wider tires out back on my car. my wheels are 17x8's. i bought some 245/45/17's to go up front but im needing some for the back. so how wide can i go on these wheels?...

 

prob 265 but they might bulge a little

 

245/40 is the widest you should run on 17x8s...

And you'll need to return your 245/45 17s, they are the wrong size and are a full inch too tall.

 

???im running 245/45's right now up front and out back with no problems...

 

Going for the 4x4 look?

I'm very surprised you haven't had fender liner rubbing issues up front with the too-tall tires. You are also reducing the acceleration of the car and creating a fairly significant speedo error by running such tall tires in the rear.