I purchased a Bridgestone rear tireand installed at 17,000 miles. I went on a long road trip which was about 6000 miles. And when I got back home I noticed the rear tire was flat like a car tire. What I mean to say is that tire instead of being rounded had become flat about 3 inches wide in the center of the tire. Most of the 6000 miles were highway miles. I am wondering if it was the highway that caused the tire to wear flat in the center of the tire. I have show it to several people and nobody has ever seen a motorcycle tire do this before. Has anyone seen this happen before?