I've really been considering....for over a year now running 17X9s in the front and 18X10s in the rear for that "raked" look.

I've found it easier to find tires in the 285/35/18 or 295/35/18 range than to find 315/35/17 sizes.

Now this is a secondary car, so tire price isn't my heaviest concern...as I put under 5K in miles within the last year. I just don't like the idea of having drag radials, and getting caught in the rain.

My question is, will there be handling or launching concerns, with the different sized rims/tires? Also, how much slower will the car be as opposed to running 17s. At this point I'm avoiding cutting springs etc.

 

The handling will suffer a little because you're adding a bit of unsprung mass (unless you find light-weight wheels), and your acceleration will go down a little because you have more weight and rolling resistance. It takes more troque to more the larger rear wheel. It's not a real big difference, though, so I wouldnt expect any real substantial changes.