Increases in engine power or braking torque are meaningless if there is no simultaneous increase in tire capabilities. We saw this in 1972, when 100 hp two-strokes from Suzuki and Kawasaki appeared at Daytona. No existing tires could deliver their power to the road. The 200-miler was won by little 350 twins in 1972 and ’73 because they were kind to tires.

A complete change was necessary, tossing out what had worked well through the 1960s and putting in its place wider, flatter-section rear tires with increased footprint area. On this new tire, Giacomo Agostini won the 1974 Daytona race, with Kenny Roberts close behind.

Ten years later, two-stroke power’s ability to overheat existing bias-ply tire structures turned GP racing into tire racing. As the other great names duked it out for first place, Marco Lucchinelli cruised several places back, waiting. He knew he wouldn’t have to wait long—bias tires were by then only lasting about ten laps, after which their tread rubber, irreversibly changed by heat, was useful only for sliding and spinning. Luchhinelli, having conserved his rubber, became world 500 champion in 1981.

Tire people knew that bias construction, in which alternating plies of fabric are placed at an angle (between 22.5 and 30 degrees) to the tire centerline, was a “heating system.” As the tread flattened against the pavement, the plies scissored against each other, flexing the rubber in which they were embedded, generating heat.



A new construction – radial-ply – replaced it. The tread became a stiff band, much like a tank’s track in that it could easily bend in one direction but not in any other. It was connected to the steel wire beads holding it on the rim by one or two plies oriented at right angles to the tire centerline. Viewed from the side, their direction was radial. Hence the name. With fewer plies and without scissoring, the reduced heat generation of this construction was the next step.

When a new technology is adopted, it takes time to fully realize its new capabilities, to optimize them, and to understand how to adapt engine power and chassis design to them. A motorcycle is a system in which all elements must be mutually adapted.

Innovation is constant. Around 2000 tire manufacturers began to employ automated tire-building machines. The classical way had existed since 1909. The tire builder stands at a tire-building drum that can be rotated by a foot control. To the right was the “servicer” – a device that on command delivered the next element of the tire to the builder. Let’s say the builder is applying a bias ply to the drum. The rubber with which it is impregnated had “tack” – a stickiness that aids assembly without overdoing it. Tack enabled the builder to stick a tire element to the drum or to the previous layer, knowing it would reliably remain in place throughout the build. The ply must be accurately centered. There cannot be air bubbles between layers. Element by element, the tire is built as a flat band. It will assume finished tire shape when it is placed in a hot mold (315 F) and a bag (rather like an inner tube) is inflated inside it, pressing it out to assume the shape of the mold’s interior. Accuracy is required. And speed, which conflicts with it.

Eventually a set of desired tire attributes was identified and given the name “Magic Triangle.” The three attributes were:

Rolling resistance (essential in reducing vehicle fuel consumption).

Wet grip – The greater tire grip can be, the greater the vehicle’s capabilities and its safety of operation (higher control authority).

Wear resistance – The customer wants long tire life - value for money.

For many years it was accepted that to improve one attribute, it was necessary to sacrifice something in one or both other attributes. Tires were a zero-sum game.

Then came 1992 and Michelin’s release of its “green tire,” which was able to break out of the Magic Triangle.

Much of tire heating and rolling resistance came from the interaction of rubber with reinforcing agents mixed into it – chiefly carbon black.

As the tire rolled, weak bonds between rubber chains and reinforcing particles were constantly broken and reformed. The energy consumed in this became heat.

Michelin had begun to use a new reinforcing agent – finely-divided silica. It had often been tried before but did not bond well to rubber chains. To make such bonds possible, chemists created silanol coupling agents to coat the silica particles, and attached “functional groups” to the ends of rubber chains, enabling them to chemically bond to the silanol. Strong chemical bonds.

Such chemical bonds did not break and reform during tire flexure, but deformed elastically, consuming little energy. Silica technology has made it possible for riders to sometimes set their fastest laps near the end of races – a huge contrast to Lucchinelli’s 1981 experience.

Too weird to be interesting? Every time you need a filling at the dentist, the UV-cure polymer now displacing mercury-silver amalgam as the filler material is bonded to your tooth using just such silanol coupling agents, applied to the tooth as a primer.

Because the needs of vehicles constantly change, tire manufacturers maintain large research establishments developing new technologies of possible use in future tires.

As I have done for many years, I report on MotoGP by trying to understand what the riders say about what they are doing. A large part of their conversation is about tires, their qualities, and about how best to conserve their properties over race distance to win or place well. This is much of what is important to them. No one can “just go for it” because tires won’t let them. In this sense, motorcycle racing remains tire racing. Today’s tires are fabulous, but so are the demands made upon them.

There has been enormous progress. In 1972 existing tires could not handle 100 hp. By 1981 the power of 500 cc two-strokes had risen to 135, forcing the change from bias to radial construction. In another ten years, engine power was 165 and it was time to break the Magic Triangle.

Today’s MotoGP engines are making between 270 and 300 hp.

What will be the next leap in tire technology?