[Mmm-Five]

They're run-flat tyres though - require a pressure sensor to be fitted as well (to be safe).

 

[Rob Plummer]

Didn't know that!

How does it all work then?

 

[Mmm-Five]

They have stiffer sidewalls to maintain the profile of the tyre after a puncture - however because of this it is unlikely you would know you had a puncture until it became dangerous - hence the need for the pressure sensors. The stiffer sidewalls also tend to reduce the ride quality and transmit more road noise into the car.