It may not necessarily be the tire, but the Combination of Rim and Tire. I have a set of Campagnolo Proton's and have had a GREAT Deal of difficulty with Continental GP3000's and GP4000's. It could be the way Continental does their tolerancing, how Campagnolo does their tolerancing, the shape of the wheel cross section, a wheel at the high side of its tolerance range and a tire at the low side or all of the above...