pin sweep can be used two ways, but the most common set up is positive pin sweep, where the front of the pins aim away from the center of the car. I have seen this on a lot of MOD set ups. Without all the fancy thinking Lessen did above, here is what I think of it as, and how it works. First, I feel it actually helps turn in harder and act as "TOE GAIN" on the inside tire. So lets say straight ahead you have 0 degrees of toe adjusted in, as you turn the car left, due to the angle of the A-Arm the left tire will start gaining positive toe, where the right tire is going to stay neutral or even be a little "behind". I don't think it will change the castor on most cars as that is adjusted with the c-hub, but it will give the feeling of increased castor. IMO