what happened to me:
I was on a century (the Windmill in Santa Maria) and heard a rhythmic thumping. I thought I had run over some bubble gum. after 10 miles. I stopped and took a look. I had bugle on both the left AND right side of the tire in a S pattern. These were New Specialized Mondos. Max 120, I ran them at 110. Ironically the sag driver was the local Specialized dealer. I got a new tire.