I’m a MotoGP novice, on a very steep learning curve. As I watched Sunday’s races in America’s so-called “Rust Belt, at the Brickyard,
Indianapolis, home of Indy 500 and NASCAR 400, the main issue seemed to be tyre management. No, it’s not about choice because, since 2009, all MotoGP riders use made-in-Japan, Bridgestone tyres, while Moto2 and 125cc use British Dunlops. But let’s stick with the blue riband event, since the principles are the same. Given the high temperature on the dry new track surface last Sunday, the riders only [slick] options were:
- Front: Soft, Medium, Hard.
- Rear (asymmetric): Hard, Extra Hard
Every rider, bar Ducati’s Nicky Hayden, opted for the softer option rear and the harder option front tyres for the 28-lap race. Hayden’s gamble didn’t pay off. While it’s the combination of rider and bike which determines tyre performance, there were clear differences in tyre durability and consistency between riders using exactly the same tyre specifications.
Allocation of the range of available Bridgestone tyres to each of the MotoGP riders is random and takes place the day before the start of
practice (Thursday in the vast majority of cases) and cannot be changed after 5pm. Restricting tyre choice to one supplier has reduced off-season testing (and related costs) as teams don’t need to experiment with the tyre allowing them to fully concentrate on [experimenting with] the bike.
A typical MotoGP race tyre comprises rubber, high tech plastic fibres, resins and minerals, combined to produce the highest level of performance. The choice of exactly which of the allocated range to use on race day is undertaken by the teams following consultation of the data they, and the tyre supplier, have collected at the track plus discussions with the riders, based on their knowledge of the circuit and expected weather conditions. The feel of the bike on test days, free practice, qualifying and the pre-race warm-up sessions also affects which tyres are selected.
On test days, and during practice sessions, riders often undertake `race simulations,´ where they ride with the sort of tyre they would
expect to use on race day. These exercises are crucial for their team, and the manufacturers, in terms of the data they yield and the feedback they produce. Based on all the available data, on race days, a critical balance has to be achieved between tyre grip and endurance. A soft ‘gripping’
tyre will permit quicker speeds and faster lap times, but will wear out more quickly. A harder, less ‘sticky’ tyre will last longer, but won’t help the rider as much to attain top speeds.
Race tyres are designed to perform optimally for a race distance of around 120km and are normally slicks: far more adhesive, but far
less durable. Race tyres can vary tremendously and, as previously noted, are chosen according to the expected temperature, the type of asphalt, the demands of the bike and the riding style of riders. To complicate matters still further, the requirements for front and rear tyres can vary massively from a technical perspective. Getting the choice right at both ends is critical to success on the track.
Races are categorised as either wet or dry before the start. However, if necessary, their status can be changed during the race. Once a race has been declared wet from the start, riders can come into the pits to change bikes, just so long as they also change the type of tyres. Once used, the tyres are all returned to Bridgestone for analysis and to aid further developments.
However, nothing and no one, prevented Aussie, Casey Stoner, from winning his 7th race of the season, his 3rd consecutive victory, and extending his championship lead to 44 points, with 6 races remaining. Completing the podium was Honda Repsol team mate, Dani Pedrosa in second, and Yamaha Racing’s Ben Spies who, having sunk to ninth place in the first lap, recovered magnificently to climb onto the podium for the third time this season. Same tyre choices, two different chassis and three different riders.
Here’s an explanation of some of the terms used when talking about tyres, courtesy of Bridgestone:-
Asymmetric tyres: These are only available as rear tyres. Asymmetric slicks comprise a harder compound in one shoulder and a
softer compound in the other designed for circuits which create higher tyre temperatures in one shoulder than the other, usually because of an imbalance of right and left-handed corners.
Bead: Serves as an anchor to hold the tyre securely to the wheel rim.
Belts: Belts are one of the core components of tyres. They may be steel, nylon, polyester or other such materials, and form a literal belt around the tyre to strengthen the tread area and to make the tyre puncture resistant.
Camber angle: Measured in degrees, camber is the inward or outward tilt of the wheel at its uppermost point when compared with the true vertical line at the centreline of the wheel. In MotoGP, camber angle has the same meaning as lean angle. Generally, the greater the lean angle, the higher the lateral force and so the greater the demand on the tyres.
Carbon black: A molecular structure found in all racing tyres, carbon black is a black powder substance produced by burning oils in a furnace. It provides strength and also produces the familiar black colour of tyres. There are hundreds of kinds of carbon black and each will produce a
compound with certain properties: improved traction, hardness, wear and so on.
Compound: Formed by a mixture of various elements used by tyre manufacturers to produce the surface layer of a race tyre, the compound’s properties vary with the exact blend of ingredients. It is the compound that is in contact with the track and therefore one of the major
factors in deciding tyre performance, being a trade-off between outright grip and durability.
Construction: The way in which the component parts (belt, cords, tread, sidewall) of a tyre are constructed determines its ability to absorb shocks, transmit traction and braking forces and to provide strength to contain inflation pressure. The nature of a tyre is dependent upon the way
in which the component parts are laid and assembled.
High-side: This where the rear tyre loses grip, either because of slippery conditions, insufficient temperature, too much throttle applied by the rider or a number of other reasons, and slides sideways . The rear then grips and tries to snap back into line with the front wheel, and the force often throws the rider off the bike.
Low-side: In a low-side crash, the front tyre will most commonly lose grip mid-corner, either because of excess corner speed, insufficient temperature and too great a lean angle or a number of other reasons, and the bike will slide out from beneath the rider.
Polymers: One of the core components of rubber, from one of two main groups: natural or synthetic.
Sidewall: The sidewall is the most important element in transferring engine power to the tyres as it connects the wheel rim to the tyre tread, and therefore the track surface.
Tyre warmer: A warming device designed to maintain a uniform temperature throughout the tyre.