Different issues come in to play, however, when run flat tyres are fitted to a vehicle that is towing a caravan or trailer says the Tyre Industry Council. In their inflated, normal condition run flat tyres may be used in the same way as a standard pneumatic tyre. Whilst a deflated run flat tyre is designed to cope with the demands of a solo vehicle, the additional mass of a caravan/trailer subjects the tyre to higher stress levels and impacts on the tyre’s in-built torsional and lateral stability. The consequence of this is that even travelling at a restricted speed of 80 kph (50 mph), the additional flexibility of the deflated run flat tyres may negatively affect the stability of the car/caravan combination.
To avoid this potential hazard, it is recommended that the distance travelled and maximum speed on the deflated run flat tyre should be reduced. As the vehicle itself has an influence on the tyre’s performance, drivers should refer to the vehicle manufacturer’s handbook for further information.
As regards run flat tyres and pressure monitoring systems, the same advice applies to a car towing a caravan or a trailer. Run flat tyres must only be fitted to a car that has been designed to accept this technically advanced tyre and has a pressure monitoring system that provides the driver with an audible or visual warning of a deflating tyre. As yet no caravan or trailer is equipped with a pressure monitoring system and hence should not be fitted with run flat tyres.