okey, i have 17" on my car and i am wondering when i go to the track, can i just take the front rims off, and put the stock tires just on the front, or should i just put all 4 back on?
It depends. I'd bet whatever tires you've got on the 17's probably have a whole lot more grip than whatever is on your stock tires so you're probably better off not changing them at all.
Traction will make up for and probably surpass the extra weight.