I might make the change to a car tire next year, but for now I'm looking for a 150-70/17 tire that gets more than 3-4k before wearing out. So far I've tried a Tourance, an Anakee and a Shinko 705. All work well but wear out the center section too soon. The front and hack rubber is fine. Since I don't do anything more challenging than dirt roads, I was thinking of switching the rear to a touring tire like a Metzeler Z6 or 880. Any reason not to, or any problem mixing them with Tourances on the front end and hack?