News & Info » The Evolution of Race Tyres

By Russell Stuckey

The pneumatic tyre was invented by John Boyd Dunlop, a veterinary surgeon, in 1888. It was intended for his son's tricycle, to make travelling over the cobblestones both faster and smoother. The year after it was patented, this tyre was fitted to a bicycle and won it's first race. These early tyres consisted of a rubber tube filled with air, enclosed by rubbered canvas, which was wrapped around the wooden rim. The method of attaching this tyre to the rim was gradually improved until it reached it's current design around 1920. Being leaders in their field, it was not long before Dunlop tyres were sought after for racing. They were Dunlop tyres that won the very first Le Mans 24 hour race, in 1923.

But these early race tyres were merely standard tyres. Tyre design then was barely keeping up with the demands of improved vehicle developments. At this stage Dunlop began developing specialised tyres for competition, firstly with the 5 Stud pattern in 1934, and then in 1946 the R1. By today's standards these tyres were very crude, being made of cotton fabric and genuine tree rubber; they weighed about 38 lbs. They were very popular however, remaining competitive until the R3 was introduced in 1955. The R4 followed soon after in 1956 as a wet weather version.

The next breakthrough came in 1958 when Dunlop introduced the use of nylon fabric with the R5, reducing weights by 12 lbs. per tyre. It was in this pattern that Dunlop introduced the first synthetic tread compound, now known as 'green spot' by its colour coded identification. In the late fifties the American giants, Goodyear and Firestone entered the European scene, however Dunlop continued to dominated Formula 1. The R6 was introduced in 1962, incorporating improved nylon casings and reduced aspect ratio. Major developments followed soon after, including the use of synthetic rubber for tread compounds and lower aspect profiles. The R6 pattern was also called the CR48 and was followed by the R7 (CR65) in 1965.

The first slick type tyre was produced by Dunlop in 1966 called the CR70. However this was ahead of its time and proved unsuitable for the compounds available then. As we now know, a tyre needs a certain amount of 'flexibility' in the tread to give it 'progression'. Without this it feels like steering a truck tyre. Earlier tyres achieved this 'progression' by the inherent flexibility of the tread pattern. Current slick tyres achieve this effect by the use of soft tread compounds. However the compounds used then were far too hard for this pattern. The next pattern development was the CR82 in 1968, a much more traditional style, which was a development of the earlier CR65. In the late '60s other developments rapidly followed, largely as the 'tyre race' developed with Goodyear and Firestone. These included extended use of depressed contour moulding, aspect ratios as low as 40, and tubeless construction.

The CR84 was introduced late in 1968, winning Jackie Stewart his first Formula One world championship in 1969.

Dunlop officially withdrew from F1 at the end of 1969 with their last patterned tyre, the CR84, citing lack of relevance to road tyre development. Interestingly, the adoption of 'slick' type treads followed immediately. At that time road tyres were rapidly changing to radial construction, then totally unsuited to the demands of racing.

Two years later, Stuckey tyre service became involved with Dunlop race tyres in Australia, first as distributor for Victoria, South Australia, and Tasmania, and later for the whole of Australia. In that first year of 1972, Australia saw slick tyres for the first time. Their use quickly spread to all categories. Australia's most important race, Bathurst, was won on slicks for the first time in 1972, by Peter Brock in a Torana. These were Dunlop slicks. Co-incidentally hand grooving was also introduced in that race as wet weather was experienced. It was Harry Firth, then manager of the Holden Dealer Team, who pioneered this development in conjunction with Dunlop Racing Service in Australia.

MODERN DEVELOPMENTS OVER THE PAST 20 YEARS:

RADIAL CONSTRUCTION
This construction was pioneered for racing by Pirelli and Michelin but first examples were uncompetitive with bias ply construction.

Michelin first produced radial slicks in 1972. Their first use in F1 was with Jody Scheckter and Ferrari in 1979. This was the first time that radial tyres had been used in f1. Michelin pulled out from f1 at the end of 1984, probably partly due to the very high cost of involvement. In those 6 years they had won over 50% of races. This forced Goodyear into producing radial tyres also. Pirelli were the first to introduce radial slicks into F2 in Europe around 1978. Several years later they also entered F1 with radials.

Radial tyres have an inherent advantage of improved traction & braking, and improved compound durability compared to bias ply tyres. This is due to the reinforcing belt under the tread, which promotes a stable, evenly loaded contact area. However this also was directly responsible for making the tyres very difficult to control at the limit of grip. Sudden 'breakaway' was a very serious problem, similar to that problem experienced with the early Dunlop CR70. Developments with radial tyres then were in the areas of making them more 'driveable'. This attribute has not been a factor in developing passenger radials for street use as it is not envisaged that tyres will be driven continually at the limit of adhesion.

Bias ply tyres have an inherent advantage for racing due to their ease of car control at the limit of adhesion. This makes them the most popular tyre for most classes of racing. However increasing limitations in tyre widths is showing the benefits of radial's durability to the extent that this construction is gradually being universally adopted.

There is now a rapid reduction in the availability of bias ply tyres. This is explained in a new article accessable here.

TUBELESS CONSTRUCTION
All modern tyres are of tubeless construction, whether for race cars, road cars, trucks or aeroplanes. Most rally tyres are also tubeless. The technical benefit is in the reduction of mass, a major obstacle to tyre performance. In practice tubeless construction also makes the tyre much more user friendly, as punctures are much less catastrophic.

COMPOUND TECHNOLOGY
As explained earlier, the original tyres were made with pure natural rubber, vulcanised and (later) compounded with carbon black for durability. Modern tyres are comprised mainly of synthetic rubber. Early commercial advantages of synthetic rubber were the stable and reliable costs compared to natural rubber, which was farmed in Asia and Africa. However modern polymers can be formulated to produce exactly the right properties required for different parts of the tyre's construction; bead, sidewall, tread etc. This is obviously crucial in the tread compound of slick tyres, but equally important for all other types of tyres. The major beneficial property of modern race tread compounds is 'hysteresis'. This is the rubber's ability to absorb mechanical energy and transform it into heat energy, which in turn lowers the rubber hardness, similar to warming up a squash ball. A highly efficient rubber ball when bounced, returns nearly all its energy by rebounding to almost the same height. This rubber displays low hysteresis. A high hysteresis rubber ball such as a squash ball will rebound to a much lower height, converting some of it's kinetic energy into heat energy. This is exactly why modern slick compounds get 'hot & sticky'.

ASPECT RATIOS
These have changed drastically, illustrating an example of road tyres following racing trends. The earliest tyres had an aspect ratio of about 100%, that is the tyre section was roughly circular, having similar section width and section height. This has reduced to about 30% for some racing (and road) applications. Surprisingly some modern racing tyres have climbed back up to about 50%, even in Formula 1!

TYRE MATERIALS
The need for low weight and strength has promoted new materials for race tyres. These include kevlar (aramid) and fibreglass, as well as other more secret exotic fibres. The current touring car race tyres as used at Bathurst use nylon casing, steel belts, nylon overlay and kevlar for sidewall strengthening. Surprisingly kevlar has readily found several applications on road tyres despite its high cost. The latest high performance road tyre from Dunlop Japan, the Formula FM-901, incorporates a blend of nylon and kevlar in the belt overlay.

Dunlop Motorsport continues to make a very wide range of historic tyres.