“Legal” does not equate to “good idea”. Cornering loads for bikes are completely different to cars. The result is bike tyres have a lot less lateral rigidity. This allows considerably more tyre deflection and can lead to exposed wheel rims or even the tyre detaching from the wheel. Views differ on how important this is on a road car of modest performance but there have been a number of racing accidents caused by this, including a friend at loton hill climb a few years back. Luckily, blockley and longstones have solved this problem.
Alan Fairless