The test, carried out in summer 2006, demonstrated that fitting a standard tyre to a car that was designed and set-up for run-flat tyres can cause a loss of performance and ultimately a reduction in the safety of a vehicle.

The results published Oct. 11 show that using a standard tyre with the same tread pattern can severely increase braking distances and reduce overall wet and dry handling.

According to the magazine’s consumer editor Kim Adams: “The message is clear – always replace run-flats with run-flats. Some drivers will be tempted to fit standard rubber when they’re worn out, as replacement run-flat tyres are generally more expensive. But you shouldn’t let your wallet decide. On a car that is designed specifically to use run-flat tyres, conventional rubber simply won’t work as well – as we discovered in our exclusive test.”

National Tyre Distributors Association director Richard Edy commented in the report: "These results reveal the folly of using ordinary tyres as a replacement for run-flats – it’s a major safety issue."

After winning the Auto Express run-flat test run in parallel with the retro-fit experiment, Andy Lane, marketing manager with Bridgestone UK, said: “Ever since Bridgestone first launched run-flat tyres, we have maintained that retro-fitting to a vehicle not set up for the technology must be avoided. We have also said that when replacing a tyre, a like-for-like replacement will ensure maximum performance and optimum safety, a statement which has been borne out by this test.”

“It has been reported that some consumers had asked for RFTs to be fitted to their vehicle even though the car was not designed for them, and in other cases drivers were opting to replace their RFTs with standard tyres to avoid the small premium on the more technologically-advanced tyre,” said Andy Lane, adding: “Thanks to these independent test results, we now have the evidence to educate motorists with absolute authority. If your car comes with run-flat tyres, stick to run-flat tyres.”