What are Run Flats?
Run Flat tyres have been around for a surprisingly long time. The idea originated in the 1930s when a car tyres suffering a blow out was a major problem. Michelin was the first main stream tyre manufacture to make Run Flats but these were used mainly for military vehicles, with these tyres being advertised as semi-bulletproof. Moving forward to today and run flat tyres are widely used by BMW in their vehicles. Also some van tyres are now run flats.
Run flats have now been made so if the tyre is punctured the driver can drive on at a reduced speed of 50 MPH for up to 200 miles depending on the tyre. There are many benefits to this tyre system. If you are on your way to work or an important meeting you would not miss it. Also you would not have to change your car tyres at the roadside. This always happens at the worst possible moment when it is raining and you have a boot full of valuable items. Run Flat tyres also reduce weight in the vehicle as with these tyres there is no need to carry a spare wheel or jack. This weight reduction would also help to reduce CO2 emissions and increase fuel economy.
The run flat tyre is designed by reinforcing the sidewall of the tyre to take the weight of the car. The car needs to be fitted with a tyre pressure monitoring system which tells the driver that one of the tyres is flat as the driver would not get any of the normal signs of a flat tyre. These signs are usually additional road noise coming through the tyres and steering vibration or shaking.
Although run flats are not cheap tyres, It is recommended that run flat tyres are only replaced and not repaired due to the additional forces that they have to deal with when they are driven on while deflated.
BMW X5 4×4 tyres are also fitted with Run Flats which gives the BMW an edge over some of its competitors in the 4wd market. If the BMW had a puncture over rough terrain it would still be able to pull its way out whereas some of its competitors may not be so lucky. Fancy changing your 4×4 tyres in a muddy bog?