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One of the most remarkable things about World Championship motorcycle racing is the way in which the transfer of the phenomenal power of the MotoGP™ bikes takes place through tyre-contact patches not much bigger than the size of a credit card.
In comparison with racing cars, motorcycling’s four-wheeled counterparts benefit from having roughly ten times as much tyre-contact surface - so it is an understatement to say that with 240 horsepower at their disposal tyre selection is critical for MotoGP™ riders. The power delivery to contact surface ratio is much greater than in any form of car racing.
There are two tyre manufacturers working in the World Championship, Japanese company Bridgestone in MotoGP™ and Dunlop from the United Kingdom in the Moto2™ and Moto3™ classes.
New tyre regulations brought in for 2009 saw the MotoGP™ class move to a single tyre supplier, for cost and safety reasons, with Bridgestone selected for the job. This single tyre rule brought with it the need for measures to ensure parity, and new regulations for the system were announced at the end of 2008. The document in full can be seen at the FIM Official website.
Bridgestone are in charge of the production of the tyres used at each Grand Prix, but their allocation to each of the MotoGP™ riders is down to the Technical Director and staff, who hand out the rubber on a random basis uninfluenced by Bridgestone, teams and riders. The allocation process takes place the day before the start of practice (Thursday in the vast majority of cases) and cannot be changed after 5pm.
In both Moto2™ and Moto3, Dunlop are the sole tyre suppliers.
The compounds used in MotoGP™ are combinations of synthetic material and naturally sourced rubber which is vulcanised and transformed into latex. A typical race tyre comprises rubber, high tech plastic fibres, resins and minerals, combined to produce the highest level of performance.
The choice of exactly which compound to use during a race is undertaken by the teams following consultation of the data collected previously at the track by themselves and the tyre supplier. Furthermore, conversations with their riders based on knowledge of the circuit, weather conditions and 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 during the race at whichever track they are practicing at, undertaking the number of laps a race entails at the respective venue. These exercises are crucial for their team and manufacturers in terms of the data they yield and the feedback they produce.
For races, a critical balance has to be found between grip and the endurance of the tyre - with all available data being used to make the decision on whether to opt for a soft ‘gripping’ tyre which will permit quicker speeds and faster lap times but wear out quickly, a harder, less ‘sticky’ tyre which will be more durable but will not assist the rider as much in achieving maximum velocity, or a tyre somewhere in between the two extremes.
In 2009 the new Bridgestone tyres in MotoGP™ had a wider operating window in terms of track temperature and were thus suitable for more varied conditions, brought about by the fact that the number of tyres and compounds available to each rider at each Grand Prix is now more restricted. For 2012 Bridgestone brought in a new compound to improve warm-up performance, which was a concern of many riders in the 2011 season.
Race tyres are designed to perform at optimum level for a race distance of around 120km.
Normal race tyres are slicks, which differ from the tyres used on everyday vehicles in that they are far more adhesive to the ground but far less durable. Race tyres can vary tremendously and 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 and getting the choice right at both ends is critical to success on the track.
For wet conditions, special wet tyres with full treads can be used, but they deteriorate quickly if the track dries out.
Races are declared by Race Direction as either wet or dry before they start. Previously, if a race started dry and rain fell, riders or officials could red-flag (stop) the race and either restart or resume on wet tyres. In 2005, a flag-to-flag rule was introduced which stated that if rain begins on a previously declared dry race, a white flag is shown, indicating that riders can pit to swap the motorcycle on which they started the race for an identical one, as long as the tyres are different.
The first instance of the flag-to-flag rule playing out was at Phillip Island in 2006, where a dramatic spectacle of the entire MotoGP™ grid entering pit lane mid-race to swap machinery was seen for the first time ever.