Explanation of why placing the upper torso on to the tank of a motorcycle in a bend, helps it to negotiate the bend.
When a motorcycle takes a bend at speed, both wheels slip sideways away from the centre of the bend.
This sideslip is essential as it provides most of the Lateral Friction Force needed to meet the demand of the Corner Force on the motorcycle; the remainder of the demand is met from Camber Thrust, which is caused by deformation of the tyre carcass, which acts like a compressed spring, resisting the deformation and pushing back against it. Camber Thrust is also a Lateral Force and along with the Slip Generated Friction Force it acts on the Contact Patches to meet the demand of the Corner Force. I.E. The Centripetal Force that is necessary for the motorcycle to negotiate the bend.