Now this is interesting. Wizard765 and I both had new Avons put on the rear of our scoot this spring. Wayne also had a new front tire mounted. The bike shop did the mounting and balancing. While riding at normal cruising speed of 90 to 110 kph all is well. It's when we get to 120 to 140 kpm that we both experince the same interesting problem. The bikes start to waddle, now notice I said WADDLE not wobble. It's not the same as with loose steering head bearings, I've had that as well and fixed it. This seems to be coming more from the back than from the front. The bike reacts as though it's being buffeted from riding behind a truck, but real steady. The tire is mounted correctly in the proper direction and runs true on the center stand. Pressure is at 42 lbs. Last night I tightened the steering head a little, now no bounce, and it improved somewhat at 120 kph, but at 140 it was not pretty and at 160 it was downright scary, but it didn't develope at all, if I held the speed steady the waddle didn't get worse and disappeared slowly as I slowed down. Any ideas?