Now that I commute to work every day on the Virago scrambler, and the roads are getting eaten by studded tyres that dig tracks in the asphalt, I have noticed that the old Yamaha is constantly toppling from side to side as I ride up or down the "walls" of these tracks. It's like it doesn't want to stay balanced. The slower I ride, the more pronounced the effect. Cannot remember ever having noticed it to this degree on any other bike. What would be the most likely culprit here, tyres, bike or useless rider?