What year is your bike @GrahamLFCkeeper ? For some reason the Avons have been known to cause the bike to wag like a dogs tail on many of the 1st gen Ventures. I myself, as well as others on the site have experienced this which seems to increase with speed sometimes coming on sudden like and as soon as the tires were removed and replaced with something else like Dunlops in my case the sensation went away. I too experiment with different tire pressures but with no luck, So went back to the dealer and he was kind enough to exchange them for the Dunlops. I am currently running Dunlop E3's front and back and the bike handles and rides like a dream.