My Pirelli snow tires had worn enough that I recently decided to replace them with Xice3. They had about 6/10ths left, which is of course still street legal but not very good for snowy conditions. (Comparison against Pirelli: they don't grip as well under acceleration, but they work a lot better on snow and ice!) When we removed the wheels I noticed something weird about two of the tires - they had a strange gouge in the tread. It was very obvious because of the trace of dust that was picked up from the shop floor before they were unmounted. You could feel a slight depression when running your finger across it. This does not line up with the upper control arm; besides I can't see how they would contact. There's also no sign of contact anywhere else. Any thoughts about where this might have come from?