Quote Originally Posted by OakLeaf View Post
Seam. Where the halves of the mold meet. Car tires have them too, if you look.

You found the one on your front tire, right, because you've already worn it off the rear.
Whewww, yes, it was the front tire, and only a portion of it. I didn't know what to think, thanks! Obviously before discovering cycling I have never looked much at tires (other than to test the pressure), or much anything else mechanical