On Racing Tyres

A Discourse Prompted by Dunlop’s Forthcoming Withdrawal from Formula One and Formula Two.

The announcement that the Dunlop Rubber Company has decided to withdraw from Formula One and Formula Two racing at the end of the year, which means that Grand Prix cars will be obliged to race on American makes of tyres in 1971, was a startling one for motor racing enthusiasts and some drivers and constructors of F1 and F2 cars, however welcome the saving in bonus payments may be to Dunlop’s shareholders, who have been having a very thin time recently.

Dunlops have made it clear that they have not entirely turned their back on the sport – they intend to continue to support sports-car races and rallies and have extended the facilities they offer to Club competitors, as announced this year in Motor Sport. Their excuse for dropping Formula One commitments, a field in which they had Jackie Stewart and March running on their product, is that there is today no very close link between the technique of making GP tyres and those sold for non-racing cars. It is true that many modern cars rely on radial-ply covers for enhanced road-holding and tyre safety at Motorway cruising speeds, whereas the roller-wide F1 racing tyre does not adapt itself to this form of construction.

Nevertheless, criticism must be directed at the publicity personnel who quite recently advertised Dunlop victories in the Grand Prix field as contributing valuable know-how to their departments engaged in making and researching high-grade tyres for ordinary men and women motorists, if reliance is to be placed on Dunlop’s stated technical reason for their F1/F2 withdrawal. Personally, I would bet that the monetary cost of ensuring that the right drivers race on Dunlop tyres was the primary cause of the Dunlop directors putting a stop to participation by the Fort in the foremost forms of motor racing.

Tyres play a curiously mixed role in modern racing. On the one hand, the almost uncanny “stiction” of modern Grand Prix cars is significantly dependent on the rubber mix of the tyres they run on, coupled with the area of rubber in contact with the road, the use of tyres which some of us think have become in width ridiculously akin to garden rollers pre-dating the use of downthrust aerofoils in this context. On the other hand, so critical of the correct “mix” are modern racing tyres that what is safe on a dry course can be impossible, even lethal, in the rain. Moreover, the durability of today’s racing tyres, which enables them to survive a complete race (and even 24-hour contests), has eliminated tyre-changing at the pits, an aspect of motor racing which held for the onlookers an element of excitement (pre-war Mercedes-Benz mechanics putting in 75 gallons of fuel and changing all four wheels in about 30 sec., for instance; today’s wheels take about twice as long to swap) and keen anticipation, which made the pit mechanics nearly as important a factor in the ultimate results as the drivers, and which gave the writers of advertisement copy an additional angle, for few (or no changes) of tyres was an accomplishment which stood out when others had to stop frequently for fresh covers.

Times change, and techniques with them. Today’s racing drivers only suffer punctures or blow-outs if a cover is damaged by a shunt or because it picks up some foreign object, such as a piece of broken suspension or a broken bottle. The effects can be as devastating as in the old days, when it was not at all uncommon for racing tyres to fling away their treads, leave the rims or just burst for no apparent reason – if you doubt this, have a word with G. Hill! All credit to Dunlop for experimenting with modern-type safety bolts.

The complexity of dry/wet racing tyres is nicely contained in a letter received from a reader, Mr. J. K. Martin, of Oxford, who wrote to us as follows, after the BRDC International Trophy Race earlier this year:-

“Well it happened again, the Silverstone weather-god went berserk on the day of the International Trophy race and delivered all kinds of weather at once – this led to that ludicrous farce of team managers and drivers trying to predict the weather in order to choose the correct tyre so as to stand a chance in the race.

“My point is that each team should try and win motor races by drivers’ skills and efficient management, and not by chance “heads or tails” decisions about the weather.

“I propose, therefore, that the idea of ‘wet’ and ‘dry’ tyres be abolished – thus necessitating the development of tyres with regard to all climatic conditions, as in ‘real’ life.

“I realise that such a tyre’s characteristic would have to be a compromise due to conflicting requirements – but then so are most things in automotive design, and I venture to suggest that such an approach would be far more beneficial to research and the family motorist (another one for the ‘do-gooders’).

“I feel that abolishing special ‘dry’ or ‘wet’ tyres would not stifle competition amongst the tyre manufacturers but would put all teams on an equal footing by eliminating the above-mentioned chance decisions, and the drivers will be at the mercy of the weather only with regard to their own skills in the given conditions, and no-one wants to make a journey to a motor race only to see their hero trail around way down the field solely because he made a wrong guess about the weather.”

It could well be that Dunlop realise that the supply of tyres for present-day GP projectiles has become a bit of a farce, unacceptable to the public at large, and that this, coupled with the fact that once upon a time drivers used to come to the Fort, helmets in hand as it were, pleading for tyres that would stand up to the tasks they had in mind, whereas, in the seventies, it is the managers, the Mr. 10%s, who arrive with contracts in their fists, asking how much lolly Dunlop will pay to sign up their drivers, which prompted this most unhappy ending of Dunlop’s long association with top motor racing.

In this connection, it was Firestone who withdrew only a few years back, quickly to rescind their decision, so it remains speculative as to how long F1 and F2 racing will be Dunlop-less. Rumour has it that they will return via their Pirelli tie-up and as Eoin Young predicts a Ferrari F2 victory before 1970 is over (they’ll have to hurry, Eoin!) it may be that the Italian side of this tyre manufactury has something of this kind up its sleeve as a let out . . .

I know nothing about that. But I find it sad that Dunlop have pulled out, because they have been makers of top racing rubber for a very long time indeed. Recent Dunlop performances in GP racing have been extremely impressive. Since 1948, when racing really got going again after the demise of Hitler (himself a great believer in the propaganda value of GP victories), they developed some 20 different GP tyres, no fewer than a dozen of these being devised during the last couple of racing seasons. Dunlop, and do not overlook this, had the virtual monopoly of Grand Prix racing from 1959 to 1965.

When Grand Prix racing began again after the 1939-1945 war, that is in 1946, Dunlop designed the first of a new series of racing tyres, the R. I. This design embodied all that had been learned about racing tyres since the very early days and took advantage of much new knowledge about rubber and textiles that had been obtained during the war. Successive post-war years showed a steady increase in the speeds at which races were won and new tyre designs were produced which made it possible to achieve these speeds in safety. These designs were identified by serial numbers after the letter “R”; in 1965 this culminated in the R.7 which dominated Grand Prix racing for several years. Today’s racing tyre is so highly developed that it can be made in different types to meet variations in race conditions. The Dunlop tyres which were successful in 1968 comprised several types, evolving from the original R.7 design.

In 1963 Dunlop introduced a “rain-tyre” in the basic R.6 design current at the time. This tyre used the same type of casing and tread pattern design, but the pattern itself was made from rubber which had a higher gripping power over wet surfaces and was called a “high-mu” rubber, This practice has continued. Unfortunately, all high-mu rubbers so far known absorb more energy and generate more heat than other rubbers. A good rain tyre used on a dry surface gets so hot that the tread is likely to break-up. Team managers must therefore make an inspired guess as to the weather likely to prevail throughout the race, selecting tyre equipment accordingly.

The current Dunlop racing designs are available in “pure-wet”, “pure-dry” and “wet-dry” form. On an average circuit the “wet-dry” tyre might be 1-2% slower in the dry than the “pure-dry” tyre and 3-4% slower in the wet than the “pure-wet” tyre. Where weather changes are likely during the race, team managers must balance the time saved by eliminating a pit stop, against that lost by slower wet or dry laps.

The profile or “shape” of a tyre is significant from several points of view. First, there is the overall “shape” of the tyre section, secondly, the ratio of sectional height to width and, thirdly, the transverse shape across the tread pattern.

The profile ratio, “aspect ratio”, or “squatness” of a tyre is the relationship between the height and width of the tyre section. Normal car tyres about 85% squat – that is, the ratio of height to width is about 85:100. There is a general tendency to squatter tyres and the latest Dunlop low profile radial ply car tyres are 70% squat; racing tyres are 40% squat, or even less.

When Firestone and Goodyear came in, Dunlop had some bad times, Goodyear claiming to “win the big ones” in 1967 – including Le Mans and Indianapolis – but by 1968, with Stewart’s skill aided by their 970 compound, on the Matra-Cosworth, they were back on winning form, causing their publicity boys to fawn on them again, and adding up to Dunlop being able to claim their (important) share of 65 Grand Prix victories and seven World Championships over the past 11 seasons.

It is rather interesting that whereas, down the decades, sparking plugs have become less and less temperamental, so that on our sports cars and GP saloons we are able to “fit and forget them”, as KLG used to say, and even racing cars no longer require elaborate warming-up on “soft” plugs, with a critically correct set of “hot” ones put in before the start, for the last 20 years or so GP cars have been enormously dependent on the dimensions and compounds of their tyres.

As an aside, surely that advertisement in which Graham Hill proclaims that he couldn’t have won his 1968 World Championship on any other plugs but Autolite because only they “could deliver the performance and total reliability he needed to win the biggest prize in motor racing”, transgresses the Trade Descriptions Act? Unless it be taken to mean that without Autolite’s contribution to his bag of gold he wouldn’t have started in the race and consequently couldn’t have won it, or that Keith Duckworth wouldn’t allow any but Autolites in his engine, for this rather than purely technical reasons. What I mean is, suppose those Autolites had been unscrewed and had been replaced by Champion, KLG, Lodge or NGK “candles”, would the performance have been so different that Hill would have lost the race? I doubt it, especially with Champion’s fine record in racing. And Autolite now seem anxious to retract their current advertisement reading: “No spark plug has ever won Le Mans. It’s just a coincidence that in 1966, 1967, 1968 and 1969 Le Mans winners were all fitted with Autolite spark plugs.” However, let us return to the topic of racing tyres . . . Yet, unless copy-writers can stretch a point to some extent, the impact of victory on sales can be diminished, which could have some bearing on the Dunlop cut-back. . .

From the very first motor race, tyres obviously played their massive part, even if they were sans air for the first such contests. As speed increased down the ruler-straight roads of France and Europe, pneumatic tyres became essential, and their adoption elevated speeds to ever higher levels. Because the pioneer races took place across the Channel, Continental makes of tyres excelled in them. Michelin gained a great reputation in the field and Michelin Cups and other prizes were given for aeroplane and ballooning contests. Michelin also pioneered the detachable rim, used in racing from 1906 onwards, when our Rudge Whitworth detachable wheels were barred from the 1908 Grand Prix by the French.

Proof that such publicity paid was evident from the store set by those who undertook the Edwardian Grand Tour in fast and powerful motor cars; until they could procure Michelin tyres they seldom felt properly secure. And Mercedes had intended to run their Sixty which beat all the French cars in the 1903 Gordon Bennett race on German-made Michelins, had not these tyres been found to contain Belgian fabric and some valve parts imported from France, which contravened GB regulations, causing Continental tyres to be hurriedly substituted. In later times Michelin took no part in motor racing. But they had little need of such publicity from 1948 when the famous Michelin “X” tyre was introduced, because this gave such outstandingly long mileages and excellent road-clinging, by reason of its unique, very supple, radial-ply walls and steel-braced treads, that it virtually sold itself to all save those with extra-sensitive cars or who drove with such abandon that the suddenness of the breakaway caught them out.

The Michelin Tyre Co. rightly guarded the supple secrets of “X” with patents and a reluctance to reveal their manufacturing methods. Now, when they no longer have a radial-ply monopoly, others, like Pirelli with the Cinturato, having been able, I think am correct in saying, to take advantage of lapsed patents and copy the “X” technique, so that radial-ply covers are now the accepted wear on high-performance cars (Jensen were probably the last manufacturer to offer cross-ply-shod fast cars, although Rolls-Royce Ltd. had reservations about the sound magnifying properties of radials until the advent of the Silver Shadow) or it could be that Michelin would benefit by participation in races, excellent as are the range of tyres they supply today, with the asymmetric XAS another piece of Michelin pioneering. Incidentally, I recall one driver (was it George Abecassis with an HWM?) who, not wishing to afford racing tyres, drove in a long-distance sports-car race on Michelin “X” and found them well able to stand up, and highly satisfactory into the bargain. But, officially, Michelin frown on racing, although Michelin XAS tyres have apparently been used in recent Formula France races.

At Brooklands, before World War One and afterwards (when they kept a 1913 GP Excelsior there for tyre-testing purposes), the Palmer Cord was the accepted tyre for racing, and was also used on aeroplane wheels, but eventually it faded away and Dunlop took its place. I dealt some months ago with the use of Rapson tyres in racing, in an article about the remarkable Mr. Frederick Lionel Rapson, whose tyres were used not only by J. G. Parry Thomas but on the road-racing Darracqs and Sunbeams of the STD racing team. But Rapsons were short-lived and thereafter the history of British motor racing was the history of Dunlop – which is why their withdrawal is so sad.

Dunlop was successful even during the Palmer regime. S. F. Edge used Dunlop tyres on Rudge Whitworth detachable wire wheels (which the French banned from the 1908 Grand Prix) on his 7.7-litre Napier when he broke the World’s 24-hour record at Brooklands in 1907, before the new Track was even opened for racing. This heavy car averaging all but 66 m.p.h. for the two rounds of the clock, required a total of 24 tyre-changes. In 1913 the sleeve-valve Argyll which took Class D records at Brooklands of up to 14 hours’ duration at over 76 m.p.h. and required only one tyre change throughout, although on this and a previous record run tyres left the rims, used Dunlops. But the Talbot which, earlier that year, had brought to Percy Lambert the honour of being the first man to motor for more than 100 miles in one hour, was on Palmers – a previous attempt had been ruined by tyre failure and later Lambert was killed when a tyre burst. On Brooklands reasonable tyre reliability had been achieved for the slower, lighter cars, even if the absolute hour record was restricted by unsuitable covers. In road-racing it was rather different. During the dramatic 1914 Grand Prix at Lyons, for example, the luckless Georges Boillot changed nine tyres before he retired, although not necessarily because of wear or punctures, as he went from plain-rubber-treated ones to steel-studded ones in an unsuccessful endeavour to overcome poor road-holding – although why Peugeot did not discover which were more effective during practice must constitute yet another motor-racing conundrum. In contrast, Lautenschlager, the winner, merely changed all four wheels on the Mercedes at half-distance, perhaps because his tyres were of 15mm. wider section than the Peugeot’s.

Even after the war the fast, heavy cars were hampered by tyres when going for long-duration records. Parry Thomas tried desperate measures in 1923 in an endeavour to keep tyres on his 7¼-litre 38½-cwt. Leyland-Thomas for a 12-hour run, such as getting a fire-engine to flood part of the Track, which merely lost him speed due to wheel-spin, and using twin rear tyres. On one attempt ten tyres deflated in six hours, two of them leaving the rims, and a flung tread injured a co-driver’s arm (flung treads also crushed the regulation mudguards on Le Mans Bentleys), the differential eventually breaking up, probably due to running too far on one rim and one back tyre.

The following year, his Leyland-Thomas better streamline and faster, Thomas went for the hour record, on Rapsons. Again tyres were his problem and, although he waited for a wet day, skids then caused additional problems. Twice tyre trouble lost him the record, which was only achieved by changing all four wheels (in 34.4 sec.) in the course of the run, the average for the hour being 109.09 m.p.h. It was 1925 before the Leyland-Thomas raised this to just over 110 m.p.h. Yet in 1932, at Montlhéry, George Eyston raised this record to 130.8 m.p.h. in the 8-litre Panhard-Levassor single-seater, using special thin-tread Dunlop track tyres on a non-stop run . . .

Another activity in which Dunlop excelled was producing highly specialised tyres for Land Speed Record attempts. For instance, in 1926 Parry Thomas proposed to exceed 170 m.p.h. on Pendine beach in his Thomas Special “Babs” with 27-litre V12 Liberty aero engine. For this 35 cwt. 500 h.p. chain-drive monster Dunlop supplied 33 x 5 tyres, with casing of 10-ply cotton, which were subjected to a centrifugal force index of 89 at 1,760 r.p.m. of the road wheels. Each front tyre supported 5½ cwt., each rear cover 12 cwt., and Thomas got the record, although conditions were only fair. He was killed the following March in “Babs” but there is no evidence to suggest that a tyre failed. Previous to this tragic accident Malcolm Campbell’s 22-litre 12-cylinder 450 h.p. Napier-Campbell, which weighed three tons, had raised the record to 174.2 m.p.h. on wet Pendine sand, with the aid of Dunlops of the same size, and type, but turning at 1,800 r.p.m., which loaded them to an index of 92, the front ones carrying 10cwt. each, those on the rear wheels a ton each.

Shortly afterwards Henry Segrave made his historic 203.8 m.p.h. bid at Daytona in the 1,000 h.p. twin-engined 44-litre chain-drive Sunbeam, which weighed no less than 3 tones 16 cwt. Dunlop made 35 x 6 tyres for it, still of 10-ply cotton, which withstood a centrifugal force of 119, running at 1,895 r.p.m., each tyre and wire wheel weighing 98½ lb., having a contact area of 19 sq. in., transmitting 13 h.p./sq.in and supporting 18 cwt. each in front, a ton on each driven wheel.

Campbell didn’t let it rest there. He took his Napier-Campbell IV to Daytona, its engine boosted to 900 h.p., with its three tons now equally disposed of, front and back. Dunlop tyres like those used by Segrave ran faster, at 1,940 r.p.m., as the car took the record to 207.6 m.p.h., but were lighter, each wheel and cover weighing 88 lb., giving a contact area of 16 sq. in., but transmitting 27 h.p./sq. in. at a centrifugal force of 120. To this Capt. Irving responded with the sleek Golden Arrow, powered by a 21-litre 12-cyl. Napier engine of 930 h.p. He required Dunlop to give him tyres which would carry 17 cwt. each, revolve safely at 2.060 r.p.m., and hold up under a force of 143. Fort Dunlop in Birmingham sent 37 x 6.00 tyres of 12-ply cotton, with a contact area of 20 sq. in. each, able to transmit 23 h.p./sq in., their weight, on Dunlop wire wheels, disc covered, up to 119 lb. each. Segrave (now Sir Henry) broke Campbell’s record, the new speed being 231.4 m.p.h. on one of the calmest runs ever, although Daytona was wet. Campbell countered, at Verneuk Pan, S. Africa, with the Napier-Campbell IV, with 100 more h.p. on this occasion. For this Dunlop prepared 99 lb. wheels and 12-ply tyres, 35 x 6.00 at the front, 37 x 6.00 at the back, slightly less heavily stressed than Segrave’s, and Campbell won back his record, with 112 m.p.h.

Sunbeam’s unsuccessful Silver Bullet, for Kaye Don, posed fresh problems. It gave 1,300 h.p., from two special 24-litre 12-cyl. Sunbeam engines, scaled a startling 4 tons 6 cwt., drove through all four wheels, had a 46/40 weight distribution, and was expected to do at least 250m.p.h. Could Dunlop cope? They could, with 37 x 6.00 14-ply covers on special Dunlop disc wheels, each assembly weighing 175lb., with a 17 sq. in. contact area at 1,660 r.p.m. Don couldn’t; he did only 186 m.p.h. on damp, bumpy sand.

Campbell tried again, his Napier-Campbell V now giving the same power as claimed for the Silver Bullet, but weighing 71 cwt. (25/41), for which Dunlop specified, and made, 14-ply tyres, 35 x 6.00 on the front wheels, 37 x 6.00 running at 2,195 r.p.m. on the back wheels, to resist a force up to (index) 163, the contact area being 20sq. in., as on the Golden Arrow. Sir Malcolm won through, at 245.7 m.p.h. on good Daytona sand.

Still the challenges came in, to the Dunlop technicians, from Wizard Smith, who did 164 m.p.h. for 10 miles on 90-Mile Beach, New Zealand, in his 70 cwt. Stewart Special, and from Campbell, who got his Napier-Campbell V up to 254 m.p.h., then installed a 36-litre Rolls-Royce aero engine in “Bluebird” and brought the record from 273 m.p.h. to 276.8, and finally, at Bonneville, to 301.1. m.p.h. This last figure posed the problem of tyres revolving at 2,805 r.p.m. on a car weighing 5 tons 4 cwt. (36/34), resisting a 266 force. Dunlop refused to be defeated and used twin 25 x 7.00 covers on the back Dunlop disc wheels, 35 x 6.00s on the front. The back wheel assemblies weighed 177lb. Up to this period, 1935, 14-ply cotton sufficed.

Now Eyston wished to reply. He took to Dunlop, in effect, a 7-ton multi-wheeled 77-litre monster he called “Thunderbolt”, encasing twin Rolls-Royce “R” aero engines developing no less than 3,600 h.p. the weight was distributed 36 cwt. on the other rear wheels. (On its 1937 attempt the distribution of weight had been 38/32/40 cwt.) Eyston spoke of over 350 m.p.h., but Dunlop triumphed, with 31 x 7.00 tyres of 10-ply Fortisan I fabric on Dunlop disc wheels having alloy rims. Revolving at the hitherto untried speed to 2,800 r.p.m., these tyres had to resist a force of 237 and transmit 46 h.p./sq. in. on a contact area of 19 sq. in. The tyre and wheel assemblies weighed 211 lb. They gave Eyston the record, twice, at 375.5 m.p.h. in 1938.

This was followed by John Cobb’s scientific approach to the growing problem of ultimate land speed. His twin-Napier-engined 2,500 h.p. four-wheel-drive Railton weighed 3 tons 2½ cwt. for its first attempt (33/30). Dunlop gave Reid Railton 31 x 7.00 10-ply Fortisan I (nylon) covers weighting 205 lb. on each steel Dunlop disc wheel, and these revolved at 2,770 r.p.m. at record speed, force 267, taking 40 h.p./sq. in. through an area of 15 sq. in. This enabled Cobb to do 350.2 m.p.h. on fair sand at Bonneville in 1938, and for 1939, and for the altered layout put the weight up to 3 tons 10 cwt. (36/34). Cobb took the record at 369 m.p.h., when the wheels were doing 2,900 r.p.m., for which Dunlop had made 12-ply tyres of the same material as before, and reduced the weight by 7lb., the force to be resisted up to 282 index.

After the war Cobb brought the Railton out in unchanged guise, aiming for 400 m.p.h., which he achieved in one direction (record 394.1 m.p.h. in poor, windy conditions). For this 10-ply Dunlops were used, but of Fortisan II fabric, although loaded to a force of 301 and revolving at 3,100 r.p.m.

By 1960 Donald Campbell had entered the LSR arena with a Bristol Proteus gas-turbine in his “Bluebird” four-wheel-drive projectile. This set a very sizeable tyre problem for it developed 4,100 h.p., increased by 1963 to 4,250 h.p., and the vehicle scaled 4 tons 8 cwt., later reduced by 2 cwt., which altered the front/rear weight distribution from 44/44 to 44/42 cwt. In fact at first the 52 in. dia. (7.00 x 41) tyres were confronted with lower centrifugal loadings and r.p.m. than on former LSR attempts. But after the crash at Bonneville at 365 m.p.h. on a poor, bumpy surface in a gusty wind, Dunlop were confronted with providing covers able to stand up to a possible 500 m.p.h. and revolving at a higher speed than their tyres had revolved before on a car of this speed and weight. By using tubeless 10-ply covers of Fortisan III they got the weight of the wheel/tyre assembly down from 305 lb. to 270 lb., with a contact area of 20 sq. in. transmitting 55 h.p. per tyre. Campbell got the record, at 475 m.p.h., at which speed the wheels were turning at 3,200 r.p.m.

I refer in some detail to these special almost-treadless Dunlop LSR tyres because they show the skill which the Birmingham rubber technicians were capable of and the tremendous contribution Dunlop made to the British supremacy and prestige in the LSR field from 1926 to 1963.

From the foregoing it will be seen that there was a time when, no matter what the Dunlop directors think in 1970, supplying tyres for the highest pinnacle of racing and record-breaking was regarded as first-class publicity for the product, and a thoroughly worthwhile technical exercise. Drivers relied on Dunlop. Not Dunlop on the drivers, for publicity in those days . . .

When I visit the London Motor Show I am confronted in the Earls Court gallery with the tyre makers’ stands. I am sure all the tyres exhibited there are excellent tyres – India, Pirelli, Firestone, Avon, Kelly-Springfield, Henley’s, Goodyear, Bergougnan, Michelin, Uni-Royal, Dunlop, Fisk, Trelleborg and Continental, to quote them in the order in which they appeared in the last year’s Earl Court catalogue. But I feel strongly that the tyres the motor-racing enthusiast is likely to consider buying for use on his own car may well be those with, as it were, a racing pedigree. Such is the publicity value of racing. Pirelli used to take Alfa Romeo and Ferrari to convincing victories and Tony Vendervell, when he was so ably promoting his race-winning British Vanwalls, obtained the supply of racing Pirellis he wanted by refusing to let Italian motor manufacturers have his Thin-wall engine bearings until Pirelli sent him tyres. But where are they today?

Firestone used to have a monopoly of Indianapolis racing and it never used to occur to me that this may have been by financial arrangement. At the time it seemed a powerful advertisement for Firestone tyres. Today Firestone field GP tyres and also had the monopoly of F3 racing until a Dunlop-shod Brabham BT 28 won at Le Castellet recently. Avon raced mainly on light cars in the old days (keeping the 11-litre V8 Wolseley Viper at Brooklands for tyre testing) and they were on the Hyper Lea-Francis in which Kaye Don won the 1928 TT, then on race-winning motorcycles, and they returned to car racing on David Brown’s Aston Martins. Last year Avon wide safety cross-ply tyres were used successfully on Formula Ford cars. But where are they today?

Goodyear still competes in F2 racing and other spheres.

Dunlop I have already discoursed about at some length. By 1924 they were firmly entrenched in the racing game, with the inimitable “Dunlop Mac” and his brother expertly fitting racing tyres under the supervision of technical manager Norman Freeman, with their own depot at Brooklands (it was still standing when last I looked) and a 1919 Indianapolis Sunbeam and one of those rather special 1924 200-Mile Race Alvises kept at the Track in which Paul Dutoit tested their tyres (he showed me photographs of them when I met him in Geneva some years ago) “Dunlop Mac” claimed in his book “Fifty Years with Dunlop” (Stanley Paul 1961) that whereas 20 Brooklands competitors were using his services in 1922, by the end-of-play in 1939 the numbers had grown to 90 motorcycle riders and 150 car drivers, and that whereas in 1926 about 75% of competitors were on Dunlop tyres by the time war came this had risen to 95%. S. F. Edge’s Napier was on Dunlops when it won the 1902 Gordon Bennet race, Rolls-Royce used them to win the TT in 1906, Dunlop tyres were on the Sunbeams which came home first in the 1923 French GP at Tours (Segrave), at Sitges in 1923 (Divo) and in the 1924 Spanish GP (Guinness) and, in spite of the Rapson invasion, Guinness used Dunlops on the Darracq which won the 1924 200-Mile Race, as Harvey’s 12/50 Alvis had done in 1923. Delage used Dunlop for some of his finest victories, and so on, right down to Stewart’s present-day successes, etc. In recent years genial Dick Jeffrey has been Norman Freeman’s counterpart in Dunlop’s International Racing and Rally Organisation, with J. C. R. Ferguson managing the rally side, and A. Davidson taking on, as it were, the role once played by Dunlop Mac. Dunlop racing tyres are designed by I. C. Mills, assisted by B. S. Bennet, and the old police-type van supplied to Dunlop Mac has a modern equivalent in Dunlop’s diesel-engined Daimler Fleetwood racing-tyre transporters. But by 1971 Dunlop will, alas, be out of F1 and F2 motor-racing . . .

I would not deny Continental a place in the market. I can recollect a picture of a Teutonic gentleman called Dietrich taking tyre temperatures for Continental at a pre-war German GP and tyres good enough for W.125 Mercedes-Benz have been good for anyone, while, I believe, Continental tyres are used today on Formula Vee cars, as they were in the 1912 Grand Prix by Peugeot and in the 1914 Grand Prix by Mercedes.

But where are the rest?

Motor-racing and commercially-available tyres are closely linked, and it is significant that those still associated with racing have appropriately-named tyres to sell to their ordinary customers. Thus Firestone have their F.100 radial, developed for and used in Formula Ford racing and the Super Sports Wide Oval “developed from the famous Firestone racing tyres”, there is the Goodyear Grand Prix tyre (G.800/Grand Prix in radial-ply form), and Avon have added the letters “GT” to their Wide Safety tyre, while Dunlop supply the splendid SP Sport, a radial-ply, aquajet-tread tyre which I am finding very satisfactory on the Editorial Rover 2000 TC, and which, with the Dunlop SP68, SP3 and the famous SP44, have been fantastically successful in rallies. And when the Dunlop directors, perhaps hoping to boost slender dividends, tell us that racing has ceased to teach their company useful lessons which can be applied to tyres for ordinary cars, they are in direct conflict with their own advertising department, which very recently has been saying that Stewart’s research at Kayalami into bolted-in racing tyres is “just part of our continuous search for new safety ideas in all fields or motoring” and that the principle behind Dunlop’s excellent new 75 Groundhog cross-ply cover is flat road contact, an idea, say Dunlop, “which we took from the racing game, where the cross-ply tyre has reached a very high pitch of sophistication”. – W. B.

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1906

“As a logical consequence of poor road surfaces and narrow-section, beaded-edge tyres with, by modern standards, poor quality rubber applied to a canvas foundation, tyre troubles were frequent. With the fixed wheels and rims of pre-1906 it was common to have a team of expert fitters at the replenishment depots, and in 1905 Gordon Bennet, the Michelin men could slash off with knives four old covers and tubes, and replace with new, in 5 min. 30 sec.”

1908

“The winner of the 1908 Grand Prix changed a rim, on average, every 40 minutes during the race [the race lasted 7½ hours] and Rigal, on his Clement-Bayard (who came in fourth), was even more unfortunate, having to change a tyre on his fixed wheels and rims every 20 minutes.” –The late Laurence Pomeroy, FRSA, MSAeS in “The Grand Prix Car, Vol. Two” (Motor Racing Publications, 1949).

1937

“Continental . . . supply tyres to both the German teams. This firm is now manufacturing four different types of tyre, made to meet the individual requirement of various circuits. There are:

Name . . . . . . . . . . Size . . . . . . . . . Tread . . . . . . . . . . . . . . . . Section

Tripoli . . . . . . . . . . 22 x 700 . . . Smooth with rings . . . . Oval

Avus . . . . . . . . . . . 24 x 700 . . . Smooth with rings . . . . Oval

Coppa Acerbo . . . 22 x 700 . . Light stud . . . . . . . . . . . . Flat

Nurburg . . . . . . . . 19 x 700 . . . Heavy stud . . . . . . . . . . . Flat

“Both the Tripoli and Avus tyres have a thin, smooth tread, specially designed for continual high-speed work, and are consequently not at all suitable for circuits where there are a lot of corners calling for braking and acceleration. For this type of circuit the Coppa Acerbo and Nurburg tyres have been developed, the former for the fast circuits with a lap speed of about 100 m.p.h., and the Nurburg tyre for lap speeds of around 80 m.p.h. – George Monkhouse in “Motor Racing with Mercedes-Benz” (George Newnes, 1938).

1968

“The first major success came at the Dutch Grand Prix in June. Here, Stewart’s Matra-Ford, equipped with rain tyres in the 970 compound, led from lap 4, went on to lap every other competitor (a unique Grand Prix performance on the Zandvoort circuit) and own the race. Jean-Pierre Beltoise in another Matra on Dunlop tyres was second. This Grand Prix started in torrential rain and although it stopped around the halfway mark, the track was never completely dry. The tyres in the 970 compound on the two winning cars had a rib removed from the tread pattern to assist water clearance; the Dunlop 1-2 win gave a convincing demonstration of the supremacy of this equipment in the rain.

“The next success came at the German Grand Prix over the Nürburgring in July, when the wet weather was possibly the worst ever seen on this circuit. Jackie Stewart’s Matra-Ford was fitted with tyres in the Mark IV variation, where a rib had been cut out. The new “extra-wet” tread compound 226 was used, on the understanding that if the track dried, (which it didn’t) a tyre change would be made to avoid overheating. Jackie Stewart led all the way and finished the race four minutes ahead of the next man.

“By now, other tyre manufacturers had begun to remove a rib in their wet racing patterns, but the next Dunlop success in the World Championship was under completely dry conditions. This was in the United States Grand Prix at Watkins Glen in October, where Stewart in the Matra-Ford led from the start and finished twenty-six seconds ahead of the man who came second. In doing this he set up a new lap record of the race of 126.58 m.p.h.; during practice he set up the highest ever lap record at 128.81 m.p.h. From the tyre angle, the important thing about this race was that Stewart was equipped with the Dunlop “dry tyre” CR.82 in 970 compound, which proved its worth at Watkins Glen in as convincing a manner as the “rain tyres” had at Zandvoort and Nürburgring.

“Similar successes in the dry were also being achieved in other Formula One events not contributing to the World Championship. For example, at the Oulton Park Gold Cup in August, where the leading Formula One teams were competing, Stewart in a Matra-Ford, fitted with CR.82 dry tyres, led the field from start to finish.

“With the arrival of the Mexican Grand Prix in November (the last major race of 1968) if Steward was able to repeat his earlier wins he would be World Champion Driver – on Dunlop tyres. The race started well for him and when he was running alternatively second and first it seemed that the Championship was in his grasp. Unfortunately, fuel starvation occurred at the crucial moment and denied him this achievement. A new dry tread pattern, CR.84, was introduced for the Mexican Grand Prix which provided increased stability.”– From a Dunlop Company Information Article.

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Some Dunlop Racing Tyres

Tyre Types

CR-65 Pattern