Modern day motorcycle tyres are packed with technology.
Manufacturers have long known how to make hard, durable rubber – but making a soft, grippy and versatile compound with high-tensile strength to deal with the power of modern motorcycles?
That’s taken many years of research!
Back in the days when you could probably have justified saying that tyres were just “round and black”, all the elements of the compound were put into a huge machine known as a Banbury Mixer, which was powered by massive electric motors of up to 50,000hp each.
The mixer then distributed the polymers, oils and other materials to make a uniform plastic mass which was then put into a mould and cured to create a tyre.
However, to create the kind of versatile modern day rubber we have available today, R&D Departments have had to look towards chemical reactions as a replacement for simple mixtures of materials.
One key component of a tyre compound is known as carbon black, which essentially acts as a magnet by attracting rubber chains to it’s surface in order to reinforce them, and this happens during the vulcanisation process in the factory. This helped to improve the rubber’s resistance to abrasion, cuts and tears.
For a long time, the way to improve a compound’s performance was to create ever-finer carbon black particles, and then find a way to mix this as uniformly as possible without overheating.
We’re now very used to hearing phrases like “silica rich compound” attached to the very latest tyre manufacturer press releases and it has long been recognised that silica, derived from quartz sand, can be used to reinforce rubber in a similar way to carbon black. The only issue when it was initially trialed, was the formation of clumps of silica during the mixing process as the silica tended to stick together.
During the 1980s, manufacturers discovered a way of essentially priming the surface of silica, making it possible to chemically bond rubber to silica particles. This bond was of much higher strength than the bond formed between rubber and carbon black, meaning that they could use relatively little silica to achieve the required strength and durability.
This resulted in a rubber compound that remained soft at lower temperatures, and it brought a new era of technology to racing rain tyres, with Mick Doohan taking a win of Michelin’s silica reinforced rain tyre at the Japanese GP in ’92. Soon after, some of these compound elements would find their way into the French firm’s dry race rubber too.
At this time, high grip rubber compounds depended on hysteresis, or internal friction, for much of their grip. The only issue with hysteresis was the increased rolling resistance and fuel consumption, at a time when government’s were pushing for vehicle makers to produce more fuel-efficient vehicles.
Thankfully with the advancement of silica technology, manufacturers were able to make the internal friction frequency dependant, so that at low speeds the rubber could flex without losing large amounts of energy, and in effect reducing a tyres’ rolling resistance.
However at much greater speeds, where extra grip was needed, the rate of hysteresis remained the same so there was no trade off in outright grip.
Prior to the introduction of silica, high-grip carbon black reinforced rubber would lose energy as the rubber strained and chains were displaced from their positions on carbon particles. The result was higher corner speeds, but lower speeds on the straights because of the increased rolling resistance.
It had taken many years of research to get to this point, and now manufacturers could start to look at other ingredients within the compound mixture.
Every element of the compound brings something to the table, and removing one can have an affect on another.
Each variable has and will continue to be tested, validated and produced on an industrial scale in order to create the versatile tyres that we have on the market today, from the latest Bridgestone sport touring tyre which is even used by Ron Haslam’s race school, to the new range of hypersport rubber which will fill the rider of a litre sportsbike with confidence in the pouring rain and allow them to push on with little interference from even the most over zealous of traction control units.
