COLOGNE, GERMANY (dpa) – Suffering a puncture is one of the most annoying things that can happen to you while driving a car.
In statistical terms a motorist is only likely to have a puncture once every two years, as major maker Goodyear points out, but that’s not much compensation when the car is stranded on the hard shoulder of the motorway.
When it happens, a driver can do little more than roll up his or her sleeves, and rummage around in the boot for the jack and spare wheel.
Manufacturers have become adept at making the spare wheel take up as little space as possible but it still gets in the way and pushes up kerb weight. Fuel consumption also suffers.
Most carmakers are keen to come up with an alternative to the traditional spare tyre.
In recent years sporting coupes short on storage space have come fitted with fix-it kits rather than a spare. Flat tyres can be bodged up with repair paste and a compressor.
Now industry is looking for a more viable alternative, a run-flat tyre-wheel combination that would enable the journey to continue.
Any solution has to include an air pressure monitoring system so that the driver is even aware of the escaping air. The technology does not come cheaply and so far systems of this nature have been confined to exclusive sportscars like the BMW Z8 or Chevrolet Corvette.
Goodyear spokesman Christian Fischer believes run-flat tyre systems will become commonplace soon, mainly because of new legislation in the United States.
Technological innovation is being spurred by scandals like the one involving Firestone tryes and Ford offroad vehicles. In order to prevent fatal accidents caused by defective tyres, the government has laid down that all new cars from 2004 must have an air pressure monitoring system.
It is too expensive for makers to fit this equipment to Stateside models only, so the sensors will probably become standard in Europe too.
Fischer believes this will mark the end of the traditional spare tyre. Harbinger of the trend is the new Mini which, as one of the first mass-produced cars with the technology, is shod with tyres which can kept rolling without air for 250 kilometres at up to 80 km/h.
Manufacturers have come up with different versions of the run-flat tyre and at the moment three rival systems can be found. Development started with the Extended Mobility Tire (EMT) from Goodyear which uses a beefed-up carcass to ensure the necessary stability without air.
The advantage of this approach, also adopted by Bridgestone and Dunlop, is that modifications are restricted to the tyres. The wheels do not have to be altered.
The alternative to EMT tyres is the Pax System. French maker Michelin is pushing ahead with this system which has been optional on the Renault Scenic for about a year. Michelin says Goodyear, Pirelli and Dunlop support the technology.
Michelin, which has a factory in Karlsruhe, has produced a special tyre with “vertical anchoring”, a claimed revolutionary technique for attaching the tyre to the wheel. When the air pressure drops to zero the tyre rests on a revolving metal suppöort ring which can carry the weight of the car.
Michelin says the system is not only fail-safe but can improve the car’s normal driving characteristics. Critics believe PAX is unlikely to catch on in a big way since switching to a completely new type of wheel will take too long.
German maker Continental in Hanover has been going down a third road after presenting its “ContiSafetyRing” (CSR) tyre two years ago.
The CSR consists of a steel ring with a flexible support, fitted between tyre and rim. If the tyre fails it is supported on the safety ring, making sure the car is still manoeuvrable. When a new tyre is fitted, the safety ring can continue to be used.
Continental spokesman Markus Burgdorf said the Conti tyre will run flat for up to 200 kilometres at a maximum of 80 km/h, with the car remaining controllable throughout. Unlike Pax there is no need to fit new rims and the system can easily be retro-fitted.
Continental recently announced a cooperation agreement with Japan’s Bridgestone to push ahead on developing the product to be launched as the ContiSupportRing.
