Optical Illusion

I was taking pictures at work today and thought I'd take advantage of the opportunity to take photos for myself while I was at it. At Galpin Auto Sports there is a 20' wall of wheels that's actually pretty cool. This is just a small section of it. When I was going through the photos in the office this one caught my eye. Are they facing to the left or to the right? And it seemed to be just these wheels. Must be something about the design. If you look at the picture for a while they appear to change direction. Anyway, I thought it was pretty cool!