Weight transfer during acceleration and braking can cause half of your wheels to unload. This is why my WRX spins her front tires, but not her rear tires when I launch my car at the strip. This phenomenon is called "squatting" when the front tires unload and "diving" when the rear tires unload.
I know that I could just stiffen up my rear springs and prevent this, but then I would suffer more rear bump steer in the corners during normal driving or rallying.
I already posted a thread about rallying, so now, How can aftemarket suspension help me at strip?