I just bought a Cycleops Mag trainer at my LBS. The tire they sold me to use with it iis a Serfas Barista City. The problem is that the tire is leaving a film on the roller. I tried following the Cycleops instructions, and tightened the roller down 2 1/2 full turns after contact, but WOW, the tire was leaving actual blobs on the roller. I have it at only 3/4 of a turn after contact, and it's better, but still leaving a tacky film on the roller. If stand to start, or test the grip with my hands, I can get it to slip a little. Are these the right tire for a trainer? I've read that some tires are harder than others.