does changing the rear tyre to a 190/55 void your insurance ? only asking as talking to a man who said his friend got a bike back from a recent claim and the tyres were marked with chalk confirming correct size etc ..
I have no experience but I would imagine that they will wriggle and squirm whenever possible so as to not pay.
If insurance can find a way out I would say more than likely. Don't forget the TCS on the Pani is set for the OEM tyres. Changing the tyre size could impact the effectiveness of that "safety" item. Irrespective of there perhaps being no change in the TCS operation, insurers may not be happy at you using a size that Ducati have not used in the bike design.
I've had insurance brokers/companies tell me that "all tyres should be the correct size and rating as specified by the manufacturer".
