Right from the start of the race until the moment the MotoGP bikes cross the finish line, there are two main factors that have a considerable impact on the motorbike's performance: fuel loss and tyre wear. A balance exists between these two closely-linked factors.
A Repsol Honda team RC213V begins the race with a full tank, 22 litres to be precise, which is the maximum permitted by the regulations. The fuel adds exactly 16.5 kilos to the total weight of the rider and motorbike, which is quite a significant amount. As the weight of the bike increases, its performance decreases — it is more difficult to reach the maximum speed and the increased inertia heightens the risk of the motorbike careering off the track at turns.
This could be a problem but, thankfully, when the fuel tank is full the tyres are still in perfect condition. Once they have warmed up, the tyres grip strongly to the surface of the track during the first few laps. After this they start to wear but, seeing as there is less fuel in the tank at this point, the lower performance of the rubber is offset. The weather conditions have a dramatic impact on the tyres: in heavy rain they suffer much less wear due to the lower temperatures and slower speed, but a rain tyre on dry tarmac will fall to pieces just as if you were using a rubber on a piece of paper.
We must also keep a close eye on the brake disks. These components, which are usually made of carbon or steel, may suffer high levels of wear depending on how they are used during the race. At high temperatures, carbon disks may even fall to pieces. That's why we use larger brake discs that distribute the heat better for races in hot temperatures, like in Sepang, or where riders tend to break heavily, like in Motegi.
Supposing that we don't drop out of the competition, the fuel tank will become emptier as the race goes on. This loss of weight means that the motorbike requires less power to reach its maximum speed. However, tyre wear means that riders must change how they control the bike accordingly. More technical riders who have gone easy on the tyres during the race can take advantage of this moment to gain a slight advantage, whilst the more aggressive riders will need to handle the bike very carefully and win back precious seconds by paying attention to the small details.
In short, although from the outside it may seem like the bikes behave the same way throughout the race, this is due to a special balance between the fuel consumption and tyre wear. The rider's challenge is to keep track of both of these at all times and know how to combine them to get the most from the bike.