One of the most interesting things over the course of the German GP was the relative performance of McLaren in qualifying, specifically, their explanation, lack of front tire temperature on full wets. In driver parlance, neither driver was able to “switch on” the full wet tire and thus not able to get its maximum performance. Ferrari and Red Bull, on the other hand, did not suffer such problems, and it has emerged that Ferrari were in fact concerned about overheating their fronts.
James Allen released an article here, where he suggests that the nature of the problem may be based in the flow of heat from the brake discs to the tires, something that teams are managing more and more with the tricky Pirelli tires.
First some background. The brake discs of an F1 car operate at incredible temperatures, think 1000 degrees Centigrade. The Pirelli tires operate at a much more reasonable temperature, somewhere around 100 degrees Centigrade. The exact operating window is very narrow for the Pirellis and teams have spent huge amounts of time understanding how they respond to heat.
Having determined the heat requirements of the Pirellis, teams now have to understand how to generate those temperatures, specifically, how to moderate them. Teams work down several paths towards that end.
The first is the driver and driving style. Recall last year, Hamilton overheated his tires, Massa couldn’t get temperature on the exact same tire. This comes down to how the driver applies the throttle and steering as well as his feel for tire slips. Small errors, such as wheel spin out of a corner, can rapidly and irreparably overheat the tires.
Second is set up. Teams use all kinds of adjustments to affect how the tire relates to the road. The most important, when it comes to tire temperatures is camber, caster, and toe. Lets not get too technical, however. Suffice to say that teams fine tune these parameters to match driver style and temperature demands.
Finally, we have ambient temperatures, or any temperature that exists outside the tire itself. Think track temperature, but also think of the hot exhausts blowing on the rear tires and think too about the break discs at 1000 degrees inside the wheel.
Brake disc heat is a big deal. It soaks the whole hub assembly in heat, including the wheel and tire.
You may have seen, though, how many teams have adopted devices whereby the team, at a pit stop, can shroud either more or less of the brake disk. This is done to mitigate the amount of heat that wafts away from the disc and into the wheel and tire. Now, sure, the brake disc will run hotter if it is shrouded more, but teams can use break materials that work at these hotter temperatures. The brakes are flexible (temperature wise), the tires are not.
Now these devices, including a Red Bull variable camber system (see rumor here), are designed to be used in practice and qualifying and if really necessary, the race. They help to avoid costly time in the garage during very important free practice sessions.
Red Bull and Ferrari seem to have gotten these systems working well, and therefore can manage heat soak from the brakes effectively to heat either the wet tire sufficiently or not overheat the tire in the dry. McLaren, not so much. They are keeping too much heat from the tire and thus not able to turn it on when it really matters.
They had better get on this problem soon if either of their drivers has a hope of challenging for the championship.