What to learn from a temperature camera?

Since the introduction of Formula One's new thermal camera images, there has been talk about the relevancy of the images, leaving apart the obvious coolness that is associated with it. It is for sure that such imaging will help people understand the complex nature of Formula One, and increase the technical interest in the sport.

Before going into what we've been seeing, one needs to take into account that the images are not meant to give away technical details that other teams could use. Instead, their calibration is not made public, making it unclear when an area is considered hot enough by the camera to be visualised as blue, purple, red, yellow or white. It is even possible that this calibration is not linear either, making it even less useful from a technical perspective. Nonetheless, the new images are worth a look, as they do certainly show a few things that were known before, but not actually visible.

At the Italian Grand Prix in Monza, FOM repeatedly showed images of the front wheels on Paul Di Resta's car. There it was clear that the sidewalls are considerably cooler than the thread, while the car's negative camber setting - a common feature in racecar setup - made sure the inside of the front tyres take the main load when the car is running in a straight line. When cornering, it is obvious how this camber setting works, as the roll of the car offsets this camber on the the outer front tyre - the one that takes the biggest load - making its thread heat up evenly across the entire width.

Now at the Singapore Grand Prix, Felipe Massa's Ferrari featured a rearward looking camera, showing how the rear tyres heat up and cool down during the course of a lap. That image showed that the rear tyres are heating up mostly during acceleration, and to a little less extent under braking. This is of course easily explained by the weight transfer of the car, as under braking, the weight shifts forward, hence also why the brake balance is set up so that more brake pressure is applied to the front wheels.

In addition, it's also clear that there is less or no camber on the rear wheels, as they have to work at their best on a straight line as well. Any minor camber angle however is easily offset by the downforce on the rear wheels, pushing the entire thread onto the tarmac under acceleration.

One final, and perhaps the most interesting observation we can make, is how the inner wall of the rear tyre is heating up. It is clear that this is mostly due to the Coanda exhausts that direct the hot stream of exhaust gases down onto the car's floor, passing alongside the tyre. This considerably heats up the rear tyres and has been a particular problem for some teams to keep under control. Mercedes AMG for instance reverted to their traditional exhaust during 2012 after finding out that their tried Coanda exhaust layout worsened rear tyre wear.

In the below clip, you will also clearly see how the tyre wall is hotter when the car is accelerating hard - due to the high RPM of the engine and hence the more powerful exhaust stream. Also look at the behaviour under braking, where downshifts are followed by a short increase in rear tyre wall temperature, again due to the increase of engine revolutions. All this of course is influenced by engine mappings, but as most teams now have a good understanding of the tyres, it's unlikely anyone is using less afterburn than possible to preserve the tyres.

Note that the only time the sidewalls of the front tyres were seen coloured, and thus relatively warm, was when cars left the pits, hence with the tyres still warmed up by the blankets.