Tyre grip has two parts, mechanical grip and chemical grip.
Mechanical grip is determined by the friction of the rubber and tarmac, and thus by the size of the contact patch which is determined by tyre pressure.
Chemical grip is the 'stickiness' of the rubber and is increased by heating the rubber.
As the rubber gets hotter, it gets softer as well as stickier. At some point, the combined 'grip' will be stronger than the rubber and it will pull the rubber off the tyre rather than holding on to the road.
At the same time, the work put into the tyre heats up the air and increases the pressure in the tyres.
The pressure affects not only the size of the contact patch, but also the way in which the sidewalls act to keep the contact patch flat on the tarmac.
The trick is to keep the tyre pressure at the optimum to retain the right contact patch, the tyre temperature at the right temperature to get maximum grip and to drive in such a manner that you don't rip the rubber off the tyre.
Track temperature and shape will determine what is possible, because all three are interconnected.
For example, if you have a track that is mostly open curves but one that is particularly 'sharp' it might be worth sacrificing speed in that corner to put less heat, less effort on the tyres but gain because you can take the other corners faster and your rubber stays in better condition.
If you start with the tyres at low pressure, more energy goes in to heating the air and the tyres cool down quicker. However, unless you can put enough energy into the tyre to keep the pressure up, you lose in mechanical grip what you might gain from chemical grip.
As far as engine efficiency is concerned, the biggest variable is altitude. A thousand foot difference in the height of the track will make the same difference as an increase in temperature of 40 degrees F.
But, if the pressure and humidity stay the same, a rise of 10 Degrees F will lop 2% off your engine power.
|
|
How does track temperature affect lap times? by 'ross' (12 Nov 2011 @ 16:33)
