This caught my eye.
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Finally, we spoke to a UK insurance company on whether fitting a car tyre on a motorcycle would affect any claims. The spokesman said "Such a change to the standard specification of the motorcycle would require prior approval from the insurance company otherwise the policy would be invalidated. In the event of an accident, the rider would lose the right to claim on the insurance. Under current UK law, the insurance company would be obliged to pay third party claims if the motorcycle rider was at fault but the insurance company would rigorously pursue subsequent compensation from the rider at fault
That alone I would think should discourage the practice.
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Finally, we spoke to a UK insurance company on whether fitting a car tyre on a motorcycle would affect any claims. The spokesman said "Such a change to the standard specification of the motorcycle would require prior approval from the insurance company otherwise the policy would be invalidated. In the event of an accident, the rider would lose the right to claim on the insurance. Under current UK law, the insurance company would be obliged to pay third party claims if the motorcycle rider was at fault but the insurance company would rigorously pursue subsequent compensation from the rider at fault
That alone I would think should discourage the practice.