BMW South Africa, which supplies the Mini and Z4 models with run-flat tyre systems as standard, intends to supply all its new cars without a spare wheel in the near future.
BMW South Africa, which supplies the Mini and Z4 models with run-flat tyre systems as standard, intends to supply all its new cars without a spare wheel in the near future.
South Africans have had a small taste of life without spare tyres since the introduction of the new Mini and, more recently, the Z4. The soon-to-be-launched new 5 Series, from the 530i model upwards, will feature run-flat technology as standard (although an emergency wheel will still be supplied) and the next-generation 3 Series will be equipped with the system.
This is how a run-flat tyre works: Extra rubber polymer reinforcement, moulded to the inside of the tyre wall, provides a cushion for the deflate tyre to rest on, whereas a normal tyre would deflate to rest on the wheel rim and disintegrate.
With the deflated run-flat tyre resting on rubber, as opposed to steel or alloy, drivers are able to continue their journey, although at a reduced speed of 80 km/h, for approximately 160 km. An obvious advantage of the system is that there is no need to stop on the side of busy or dark roads where changing a tyre could be dangerous.
Another advantage of having a side wall that remains rigid is that in the event of a blowout the driver is more likely to retain control of the vehicle as the sudden loss of balance is compensated by the extra rubber, BMW SA claims.
While requiring special EH2 (or extended hump) rims to house the extra technology, run-flat tyres also need a tyre pressure monitoring system in place in order to work efficiently. The early warning of a loss of tyre pressure is required in order to alert the driver to take the necessary precaution of reducing speeds.
Besides the safety advantage, baggage space increases by virtue of no spare being kept in the boot. There’s also an overall mass reduction because the weight of the extra wheel, and jack, is saved.
Most major tyre manufacturers offer run-flat specification tyres – but in BMW’s case different brands are supplied for various applications. For example, run-flat tyres manufactured by Goodyear are fitted to Minis and Bridgestone 17-inch examples will be fitted to the 5 Series and Z4.
“Goodyear and Bridgestone tyres are currently standard on the Mini and Z4 respectively and BMW SA’s policy is to use the specification tyres that best suit its run-flat systems,” BMW SA spokesman Clynton Yon told CARtoday.com. “However, we will not only use one particular brand of tyre for each different model. Continental, Michelin and Dunlop are understood to be making run-flat tyres that will be compatible with BMW’s model lineups”.
Stiff competition between brands will in all likelihood lead to reduced prices for these tyres in the long run. However, BMW South Africa says that run-flat tyres will cost approximately 25 per cent premium more than “ordinary” tyres.
With EH2 rims being able to accommodate either run-flat or normal tyres and with each tyre manufacturer developing their own products it has been agreed that a universal “RSC” (Run-Flat System Component) logo will appear on all tyres that qualify.
