Before it even begins, it seems more than likely that the 2023 MotoGP season will be all about front tire pressure management. Multiple signs seem to indicate this, from the problems encountered more and more frequently by certain drivers to the sanctions planned this year by Dorna Sports, and this is why it seems useful to us to study in depth a subject of which very few people imagine today the importance and the level of technicality.
1/ The beginnings…
October 2016, Phillip Island. After winning the Australian Grand Prix following the crash of Marc Márquez, it's a Cal Crutchlow euphoric who declares “I was afraid of falling, so I was very careful when braking there. I knew it could be very dangerous there. I came across this place two years ago and was afraid of making the same mistake. At the same time, I knew I had to go fast, otherwise my front tire would get cold. When Marquez fell, I decided not to let go, because the tire would have cooled and there would have been a greater chance of falling. In the last 10 or 12 laps I didn't push at full speed, I just made sure the tire stayed warm. When the sun hid behind the clouds, I drove a little faster so the tire wouldn't get cold. »
We know the resounding declarations of the friendly British pilot and, at the time, we took this last sentence as a customary exaggeration of Her Majesty's representative. Except that the LCR rider was completely right and, for the first time publicly, pointed out what would become one of the most important areas of work in MotoGP…
2/ The problem…
Like its rear counterpart, the front tire needs to work at a certain temperature to function properly. Cold, it offers almost no grip and provides no sensation to the driver. This is why it is brought to temperature using electric blankets or in a warming cabinet, to around 90°. Then, it is up to the pilot to maintain it at its operating temperature, around 100°.
The lower the pressure, the more the tire carcass will work by deforming and generating temperature. The objective is therefore to get as close as possible to the minimum limit of 1,9 bars imposed by the regulations (compared to 1,7 bars at the rear). All settings are made in this direction but the operating range is very narrow: too low, the pressure will be penalized (at least in theory, as we will see later), too high, the tire loses a little grip but above all no longer offers any sensation to the driver, with the obligatory slowdown (this is what happened to fabio quartararo several times) or the risks of falling that result…
3/ Why such instability?
Due to the very low volume of air in the front tire mounted on its rim, the pressure and temperature are absolutely not stable and vary very quickly and considerably in the face of a multitude of factors, among which come first the initial pressure, the temperature of the track, the ambient temperature, the pace imposed by the rider and the position of the motorcycle on the track, isolated or within a group.
4/ Examples…
To illustrate the lack of inertia in pressure, and even more so in front tire temperature, it is enough to listen to a few examples among those entrusted to us by the tire managers of certain MotoGP teams. It should be noted here that the latter insisted on remaining anonymous, which was the only way to obtain information that was both concrete and quantified without causing them any problems. This information should therefore not be placed in the “we say” but on the contrary first-rate elements!
Here is an anthology which allows us to grasp the scope of the subject, transcribed and translated word for word from recorded conversations…
“At the front, the tires operate around 100°. At the rear, you can exceed 120° when racing. »
“A driver who leaves the box and is waiting for a wheel, this is immediately visible on the clock but also with the pressure which drops very low, especially since the discs are not hot, the rim is not hot . This is why today we ask the drivers to be straight on their feet, especially if they come out with a slightly hard tire. You have to be nervous from the first braking to keep the tire temperature, otherwise it's a vicious cycle of tire cooling. »
“0,05 bar is already a standard step for us, and it is the difference that we must put on the rear tire in racing or in FP4 when we start with relatively full tanks, with between 12 and 15 kilos of gasoline. It heats the tire much more than in qualifying mode where you start with only 4 or 5 kg of gasoline.
At the front, there are many more factors at play: the suction phenomenon and braking with the discs which rise to almost 1° and which transmit all the heat to the rim and the tire. At the front, we have 000 bars of leeway for the tire to function correctly, because we have a minimum of 0,2 bars to respect and above 1,9 we start to have locking wheel. The problem is that during certain races like in Austria or Motegi, the pressure can vary from 0,4 to 0,5 bars. We must therefore make compromises and take the risk of starting below the limit so as not to finish the race at 2,3 bars, where the bike is undriveable because it no longer warns. »
“There are circuits like in Argentina where, even in the race, the pressure is the same every lap. On others, it goes up, up, up… It's unmanageable! »
“Too much pressure at the front is dangerous for the driver, but not enough pressure, with the Michelin carcasses which are very flexible, it is very unpleasant and very uncomfortable because there is no longer any support. »
“On the curves, we see if the driver has taken an aspiration or not. Several revolutions in suction, that's 0,2 bars more pressure in the front tire, which roughly corresponds to around twenty degrees. »
“During practice sessions, the pressure builds during the first six laps. In the race, it can be 12 or 13 laps. This is among other reasons why it is almost impossible to have the right pressure during the two rounds of a qualifying run, which is what the organization would like in 2023: it will be either in the first or in the second , but not in both. It's impossible ! »
“A straight line without vacuum and the front tire can lose around twenty degrees. »
“It is clear that depending on the way the driver enters the box, and the situation of the latter in the pit lane, there are huge differences in the measurement obtained by taking the pressure. A driver who pushes hard on the first two sections before starting to slow down in the third, then returning to the box, is often 25 or 30° more than the one who does his last lap eight seconds behind the normal times. »
“Pressure has a little more inertia than temperature. This can go down very quickly at first, then more slowly afterwards. The pressure will take a little more time to come down. »
