hello there
i just bought a new impreza 06 2.0 R
it came with 15'' common wheels and 195/45(not sure) tires
i want to ask you if i upgrade them to 16'' or 17'' wheels and 245/55 tires, will it make a decrease in the performance or the speed of my car?
thanx

 

Yes - to maintain the same diameter/circumfrence/gearing you could go to a 205/40/16 - go to tire rack and see how to do a +1 (16" rims) or +2 (17" rims) and their tire computer will answer your questions (you can play with various scenarios there - quite cool)

Actually - you need to start with more accurate info than you have provided - best to you

 

www.tirerack.com For your education on tires/rims and +1/+2/+3 setups.