I've had my new Goodyear Wrangler Duratracs about 1500 miles and really like them. My only complant is at freeway speed, I'm getting a pretty good shaking. Of course it only happens between 57 and 70 miles per hour. Is this going to be the way it is for the next 3 or 4 years? Should I bug the guys I bought them from? Suggestions please. Thanks.