I had a talk with a very well informed Michelin tire rep today. I asked him about the change that were made in the Scooter tire when they changed from the Michelin Gold Standard to the Michelin City Grip.
The tread design is the obvious change but the rest of his explanation I found very interesting. The tire is made in two pieces. The tread is heat bonded to the tire carcus. The tread is made of a changing blend of rubber. The center part of the tread is made of a harder rubber to give the tire longer highway tread wear. As you roll over the edge the rubber gets softer giving you increased traction as the turn gets tighter.
I don't know if other tire manufacturers use this technique but I thought that it was worth mentioning.
Sorry for the error. The name of the tire is City Grip Not City Street.