A PNEUMATIC BRAINWAVE A TYRE THAT CAN SAFELY BE DRIVEN AFTER A PUNCTURE

Press, Volume CXII, Issue 32860, 8 March 1972, Page 16

A PNEUMATIC BRAINWAVE A TYRE THAT CAN SAFELY BE DRIVEN AFTER A PUNCTURE

(By

JAMES ENSOR,

?, in the "Financial Times," London)

(Reprinted by arrangement)

~ Du ™?' the Past few weeks engineers and product planners of all the major European car manufacturers have been flying down to the Paul Ricard motor-racing circuit at Le Castellet, near Marseilles. They have been shown a remarkable and unusual demonstration, which they reportedly received with considerable enthusiasm. News of the showings leaked out prematurely in the Midlands and has led to considerable speculative buying of Dunlop shares, which pushed the price up to 199 p 20p up on the week.

Although the speculators will have to wait at least three or four years before Dunlop’s profits show any response to the product which it unveiled at Le Castellet, their basic reflex was right. Ultimately, Dunlop’s invention will probably be ranked as the most important development in tyre design since Michelin’s engineers perfected the radial tyre before the last war.

The engineers at Paul Ricard were able to watch cars being driven around on two or three deflated tyres at speeds of 50 m.p.h. They saw a Ford Capri suffer a blow-out at almost 100 m.p.h. without being deflected even momentarily from its straight course. They have seen a

Ford Escort with one flat tyre drive for over 100 miles at a steady 50 m.p.h. without tyre damage. And they were able to drive a variety of European cars themselves, making sharp cornering movements without hazard, with one or more tyres punctured.

None of these demonstrations would be possible with an existing, conventional tyre. A high-speed blow-out in a front tyre would, in all probability, lead to a rollover accident and probably to loss of life. A slower speed puncture would rapidly twist a conventional tyre off its rim, destroying the tyre, damaging the rim and giving the driver the feeling that his car had a square wheel.

Over a quarter of motor accidents where vehicle failure rather than driver error are the cause, involve punctures, Dunlop’s research suggests that there are 30m punctures each year in Europe and that half of these cause what the driver describes as “a major nuisance.” If the driver is a woman, the odds are three-to-one that she will not know how to change the wheel unaided. Even with male drivers there is at least one chance in four that the spare tyre will be unserviceable, leaving the motorist stranded. This research convinced Dunlop’s sales staff that the biggest contribution its tyre designers could make would be to develop a tyre that could be driven safely after a puncture. This, in essence, is exactly what the Dunlop “Total Mobility” tyre achieves.

Dunlop has been developing this tyre for two or three years, and the idea had been a gleam in the eye of its chief tyre designer, Mr Tom French, for much longer than that. The company has already spent some £jm on research and development, but French is now satisfied that all the technical problems are either solved or easily soluble and Dunlop is ready to show its invention to the car and tyre makers and safety experts of the world. The company has taken out over 30 patents in every major country and believes that it is the only major tyre, maker that has been working along these lines. A low, fat tyre The basis of the “Total Mobility” tyre is a fairly ordinary radial tyre such as Dunlop’s SP Sport, with a very low “profile ratio” of 60 per cent That means that it is a low, fat tyre considerably broader than it is deep. The tyre must be fitted to a special rim which the wheel division of Dunlop has developed and which prevents the tyre ever slipping off, even when punctured and cornered hard and fast

The tyre is lubricated internally by a cupful of special fluid, about which Dunlop is keeping very quiet. When the tyre punctures, some of this fluid vapourises, seals the aperture and helps to maintain a slight pressure inside the tyre. But it also lubricates the tyre’s internal surfaces and prevents an excessive build-up of beat inside the tyre. As the tyre flattens, the rim of the wheel drops until it is running on a double band of rubber, with the tyre squeezed underneath it. Tyre and wheel are designed in such a way that the rim never slips off this band, as it would straight away with a conventional tyre. Instead, the rim continues to roll along over the rubber, and while the ride of the car is more bumpy and the steering a bit heavier, the car remains just as controllable, driveable and safe as before.

The inner rubber surfaces of the tyre slip against each other at a relative speed of over 20 m.p.h. But provided that the car is not driven for a sustained period at over 50 m.p.h., the lubricant is able to cope with this and to prevent a frictional heat buildup that might destroy the tyre. The basic principle of the Total Mobility tyre is as brilliantly simple as that. The tyre, of course, needs special rubber compounds, stiffer sidewalls and different inner liner compounds as well as the vital lubricant. But its basic design is little different from a standard radial tyre and it will be possible to manufacture it with the same machinery. Tom French says that there were no really fundamental problems in developing the tyre, although some secondary development work still has to be completed. The advantages of such a tyre are obvious and considerable. It gives the motorist complete mobility after a puncture. It is safe in a blow-out. And it continues to provide a good steering response after a slow leakage. It eliminates any need to carry a spare wheel and it provides better tread life than a normal tyre. It will be at least two years, however, before the Dunlop Total Mobility tyre is fitted as original equipment on any European car. Production will start next year, after the few remaining problems of fluid encapsulation, wheel sizes and fitting have been overcome. However, nowadays

tyres and suspensions are designed together, so that cars

will have to be modified and altered to make them suitable for the new tyre.

The Total Mobility tyre is a much “lower” tyre than most of those used on current saloon cars. Only Lotus, in Britain, as yet uses a 60 per cent profile tyre, and it has encountered some problems with vibration and harshness. The Jaguar XJ6 uses a 70 per cent profile Dunlop tyre, but most cars have 80 per cent profile tyres. Cars will have to be adapted to take the new tyres because most current models would have inadequate ground clearance or mudguard clearance problems. The designers will have to modify suspensions to eliminate road thump, vibrations and the harder ride that can be associated with such tyres.

Once these developments are made, there seems to be every likelihood of the Total Mobility tyre becoming widely adopted. It will be more expensive than existing tyres—a set of four, in fact, is likely to cost between 10 and 30 per cent more than a set of five radial tyres, even at volume production prices. But, in compensation, its life should be at least 60 per cent longer than that of current 80 per cent profile radial tyres. Luggage space saved The manufacturers of small, European cars are likely to be the most immediately interested in the new tyre. Fiat and Renault have both shown some interest, while Mr Harry Webster, the chief engineer of Austin-Morris, is enthusiastic about its properties. Obviously the amount of luggage space released in a small car by dispensing with the spare wheel could be an important sales factor.

For this reason, too, sports car manufacturers are likely to be among the first to adopt the new tyre. Some sports cars are already equipped with low profile tyres and it would be relatively easy to adapt them for the new one. Also, the safety aspects are more relevant at high speed, where blow-outs can be really dangerous. It seems probable that one of Dunlop's traditional best customers, probably British Leyland, will be the first to use the new tyre, possibly initially as an optional extra. But the invention seems to be such a significant one—in terms of both safety and convenience—that I would expect Dunlop to license it quite widely to other tyre manufacturers. There would seem to be little doubt that the concept of the Total Mobility tyre will eventually be widely adopted, at least in Europe, both because of its greater safety and its convenience. But the timing is another matter. It has taken the radial tyre 30 years to displace the cheaper but inferior cross-ply tyre in the major European markets and in the United States it is only now making some impact. The spread of the Total Mobility tyre is likely to be just as slow because of its greater expense and the need to redesign suspension characteristics to mate with it

The market initially will be confined to Europe, because the tyre can only be built ,as a radial and it is only the European tyre manufacturers who have the appropriate machinery to make radials in quantity. The total sales of European tyre makers last year was something over £2ooom, but this includes products like Dunlop's wheels and sports goods and Pirelli’s cables as well as tyres. Obviously only a fraction of these sales will be accounted for by the new tyre—at least for the first five years. Dunlop’s marketing director for tyres. Mr Gordon Shearer, has shrewdly refused to make any market assessments for the tyre as yet. Much will depend on whether other European tyre makers such as Michelin and Continental are prepared to take out licences. As Mr Shearer admitted while Dunlop is able to meet the initial demand that is likely to develop in Britain, France and Germany from its own local plants it would not be capable of meeting the requirements of even half the major European motor companies. The attitude of national safety authorities may prove to be a critical factor. It is currently an offence to drive in Britain on a deflated tyre. Dunlop feels sure that this rule will be waived for its new tyre; otherwise it will not be able to sell it

But it is equally important that the safety authorities should actively encourage the use of products, like this tyre, which promise to save lives. The example of the Dunlop Maxaret, an antiskid device which could be manufactured in volume for perhaps £5O or £lOO, yet has remained unused through general apathy, is a sad precedent. But I do not believe that the Total Mobility tyre will suffer the same fate; it offers a way of avoiding nuisance as well as reducing accident risk, and that is a much more powerful marketing factor. ,