Runflat safety... But at what cost?

They have been hailed as the saviour of tyre safety and convenience; with the ability to both help you maintain car control in the rare event of a blowout and alleviate the potentially hazardous need to change a tyre on the side of the road.

They are run-flat tyres. And increasingly they are being specified on prestige or premium vehicles being sold in Australia. German carmaker BMW Group has taken the lead with this technology, having first fitted them to some 5 Series models in 2003 in Australia and now featuring them as standard on all 1 series, E90 3 Series sedans, Z4, 6 Series, 5 Series with 17" or 18" wheels, and Mini Cooper S models.

While there is little doubt about the safety perspective -- after all, tyres are the single most important safety feature of your car -- there is growing concern in Australia about the convenience claims and the cost to end users. For in the runflat world, there is an empty space where the spare used to sit in the boot.

On the safety front, runflat tyres are designed to enable the driver to maintain normal control of the car in the event of a blowout and ensure that the car can still be driven even when the tyre has lost all its air. With stiff sidewalls -- or in the case of Michelin's PAX system, an inner support ring -- the burst or punctured runflat tyre remains on the rim and can be driven safely up to 250km depending on the load in the car at speeds of up to 80kmh. This is usually far enough to get you to the nearest service centre.

The runflat tyres are linked to a tyre inflation sensor which alerts the driver if there has been a loss of pressure so even if you don't notice a tyre deflating, you are forewarned, enabling you to ensure the tyre is replaced (or the pressure loss investigated and addressed) before it becomes critical.

The technology does have obvious benefits from a safety perspective, however, as with many technological and safety advancements, there is a price to pay and it is not only financial.

Five of the major tyre manufacturers including Bridgestone, Dunlop/Goodyear, Pirelli, Michelin and Continental all market run flat tyres in Australia of varying sizes and all supply original equipment tyres to various BMW models.

This means, for instrance, that even a small leak caused by a nail in the tread  will require the tyre to be completely replaced. Costs vary depending on the tyre and specification but range from about $300 for a 16-inch Bridgestone runflat for a Mini Cooper S -- quoted by a central Melbourne dealer -- through to $424 for a Continental 16-inch tyre for a 320i. In the case of 17 and 18-inch tyres the $$$ mount up. Runflats in general carry about a 20-30 per cent price premium over the equivalent 'traditional' tyre.

According to Jeff Moorhead, Dunlop/Goodyear's technical marketing manager, the company received a directive from its technical centre in Europe that it can allow repairs to its runflat tyres which run under the names of EMT (extended mobility tyre) or DSST (Dunlop Self Supporting Technology.

"At this point in time we have a policy of repairing them in the same way as you would repair a normal tubeless tyre with a puncture. It [the tyre] has to be inspected in a fairly rigourous way and being run flats they inspect them in a more rigourous fashion and they will be looking for telltale signs to see if it has been driven too far," says Moorhead.

"But the edict out of our technical HQ in Europe is that they will allow repairs to be done in the normal way with the appropriate inspection process."

If appropriate you can have your Dunlop/Goodyear tyre repaired at the "vast majority" of Beaurepaires or Goodyear Auto Service Centres with Moorhead saying that the bulk of the 520 national outlets are trained and equipped to repair the tyres.

He says the equipment needed to fit runflats is no different to that used for specialist low profile performance tyres.

"A lot of low aspect ratio tyres suffer from a similar problem in that they are really tough to fit and you really need the modern overhead machine which has a second arm on it, so there is an increasing number of dealers out there that have the equipment to do it. You fit them (runflats) in a conventional way with a fair bit of extra care and attention and good modern equipment," Moorhead says.

While none of the other manufacturers will allow the tyres to be repaired, they also have fewer outlets equipped and trained to fit replacement runflat tyres. Bridgestone has just 59 authorised RFT centres nationally while Continental has between 50-60. You can obviously also have the tyre replaced at one of BMWs 40 dealers around the country.

The major distribution centres are in Melbourne and Sydney and like many specialist tyres, runflats would need to be airfreighted to wherever you have had your puncture.

If you are in a major metropolitan area, this doesn't pose too much of a problem as you may still be able to drive on the punctured tyre but if you are out in the country and have already used up your maximum travelling distance just getting to the tyre service centre then be prepared to stay put until your tyre arrives.

According to Dunlop's Moorhead, this is a growing issue and not just with runflats.

"The array of tyre sizes that are now in the marketplace is massive and it has grown in quantum leaps in the past five years and this is another issue on top of a fairly big problem for the industry in terms of proliferation of sizes," he says.

"If you have got a niche sort of vehicle, you can't expect to go into a tyre service centre in Swan Hill and think you can get a tyre off the shelf. It is part of the overall increasing challenge we face in terms of proliferation of sizes and types."

According to BMW spokesman Alexander Corne, most of the company's customers would not be put off by the fact that they may have to wait to have the tyre replaced or the potential added cost of a replacement tyre - as opposed to a repair.

"If you have got a $100,000 car, as it is a high performance machine, you might not want to plug the tyre and secondly you might have to wait half a day for the tyre to come from the distribution centre to the retailer but you can still drive your car around safely because you have got the runflat," Corne says.

Corne says even those that buy cars at the lower end of the BMW market, the new 1 Series for example, would not be concerned about the extra cost of having to replace a punctured tyre.

"There are people who make a decision to buy a 1 Series not because it is a $45,000 car but because it is a small compact BMW that suits their needs. So whether they would be the type of people who would plug a tyre to fix a puncture or whether they would be the sort of people who would insist on having a new tyre put on for piece of mind, I think the latter is probably more likely."

As the cheerleader in the whole runflat debate, BMW is pushing the tyre's safety and claimed convenience and is slowly adding more models with runflat tyres.

Runflats may offer improved safety but if you have to wait up to at least a day to do what you can presently do in about 15 minutes, it is arguably not what one would call convenient.