Bridgestone DriveGuard: run-flats for everyone?
Bridgestone DriveGuard: run-flats for everyone?
Having experienced several ‘flats’ in my motoring career, I am not being melodramatic by commenting that a sudden tyre pressure loss can be life-threatening. Not only are punctured tyres a major factor in GEM Motoring Assist members’ reliance on our breakdown services but many members have also voiced concern about the tendency for spare tyres being usurped by a weedy aerosol of sealing ‘gunge’ and a light-duty compressor for emergency situations – the use of which is not always successful and the affected tyre can even be rendered non-repairable by doing so, in some situations. The practical safety issues of trying to deal with a puncture at a busy roadside must also be a consideration.
THE TRADITIONAL COMPROMISE
Self-supporting run-flat tyres have been fitted to certain new cars (particularly BMW/MINI) for over ten years but the safety benefits, which reduce the risk of the driver losing control and breaking-down in a dangerous location, have brought serious engineering downsides.
Initially, the very rigid tyre wall construction sacrificed a comfortable ride quality. Tyre fitters also tend to vent frustration at the increased forces needed to remove and replace the stiffer run-flat tyres from wheel rims. Furthermore, run-flats’ higher weight increased the rolling resistance and harmed fuel efficiency. These issues have become less of a problem, as the technology has developed but many motorists are put off by the extremely high replacement costs. The popular installation of conventional, non run-flat tyres, on a car thus-equipped from new, loses the obvious safety benefits instantly and can affect the vehicle’s handling characteristics, in certain circumstances.
Even so, the safety benefits of run-flats are considerable, where the tyre structure is suitably reinforced to support the vehicle’s weight for limited speeds and distances, with zero internal air pressure. Bridgestone, the World’s largest tyre maker, has investigated how the latest benefits of run-flats can be retro-fitted to older vehicles, without introducing the traditional drawbacks, including a major price difference. While the technology has been available in North America for almost two years, the DriveGuard range was launched to the European media on Tuesday past.
ADDRESSING TRADITIONAL CONCERNS
To assess whether, or not, fitting a DriveGuard is going to destroy the comfort of a typical everyday used car, I tested two Peugeot 3008 diesel hatchbacks on a broken-surfaced mountain road (one of which was shod with conventional Bridgestone Turanza, the other, fitted with DriveGuards), in which I found any denigration of ride quality to be barely detectable. Due to the low speeds involved, which did not exceed 40mph, it did not seem that the DriveGuard produced higher levels of tyre roar, although I would have preferred to drive at motorway speeds to confirm this. Bridgestone also reports that the new materials used in new run-flat tyre range are also fully recyclable.
DOES IT WORK?
The more telling exercise was driving another 3008 for 15 miles, after an industrial nail had been driven through the nearside front tyre’s sidewall. While appearing to be slightly deflated after all the air had escaped, as the structure’s sidewalls shouldered the weight of the Peugeot, another drive up-and-down a twisty mountain path revealed that the car’s handling had hardly been affected. I was confident to tackle sharp bends at speed, with the tyre neither coming off its rim, overheating, nor falling apart. While there was a slight increase in the tendency for the car’s steering to follow ruts in the road, an illuminated tyre pressure sensor (TPMS) warning lamp and a subtle, but intentional, ‘buzz’ from the deflated tyre were the only clues that a deflation had taken place. Therefore, I feel confident in the maker’s claims that the car can be driven for up to 50mph for 50 miles, before requiring removal from the rim. Interestingly, punctures can be repaired with traditional methods and tyre fitters will be relieved to hear that the designers have considered making their removal as easy as possible and that no special training will be required, meaning that the costs of repairing a puncture should remain the same as those of a conventional, tubeless cover.
Bridgestone also claims that the tyre’s ability to tolerate the punishment that I exacted on it is down to the design, enhanced rubber compounds (which are neither exotic, nor expensive) that can tolerate the hotter conditions created in zero pressure situations and enhanced external mouldings to create air turbulence that increases cooling of the outer tread and sidewall surfaces.
WHAT WILL THE NEW RUN-FLAT COST ME?
Despite my enthusiasm, Bridgestone has not reinvented the wheel. Yet, bringing the latest safety advantages in tyre technology within the reach of a typical used car owner is a bold move that should made a significant positive contribution to road safety, with the provision that used car owners (and fleet managers) can be convinced.
While realising that purchase cost is a significant problem with run-flats, Bridgestone admits that it expects the cost premium to be between zero and 10% over that of its already premium-priced conventional tubeless tyre. We wait with interest whether, or not, the company honours its pricing intentions, when DriveGuard becomes available to buy in the UK from April.
Will DriveSafe fit any car?
Only cars equipped with tyre pressure monitoring sensors (TMPS) should be fitted with DriveGuards Yet, buyers can retro-fit the sensors but must only invest in quality parts that comply with ISO standards. At its introduction, Bridgestone will market DriveGuard in the most popular tyre sizes, prior to widening the size range and introducing cold-weather tyre rubber compounds, depending on the public’s appetite.
We hope to report on the retro-fitting of these tyres, as well as their real-world performance, after they become available for retail sale in the spring.