Very difficult to tell when it is happening, Pete, but the scuffing on the bulkhead suggests it could even be happening in the steering straight ahead position too, possibly when pot-holing with two up. All the contact evidence is on the bulkhead with no damage obvious on the tyre suggesting only momentary contact.
In unloaded static condition there appears to be ample clearance between tyre and bulkhead so difficult to visualise how it is happening.