Our Experts on: Hot Tyres and the Grand Prix
Our tyre experts are a bit motorsport mad over here at CarbonBlack, so they’re currently quite engaged in the Melbourne Grand Prix. This year, the high temperatures generated trackside at Melbourne during the first 2008 Formula 1 Grand Prix brought quite a bit of comment about “Tyre Grain” and its effect on tyre adhesion. Here’s one of our tyre experts, David Matthews:
During a race tyres generate heat, mostly within their interior. The most heat is produced when the tyre is new, and gradually declines as the tyre wears away its rubber tread and settles in, the latter happening very quickly at formula 1 speeds. But the heat generated in the tyre can’t get away quickly when the road is a hot 52 degrees, and the ambient temperature is in the high thirties as it was in Melbourne.
The tyre surface rubber undergoes a chemical change called “reversion’, the physical state changes, it becomes less resilient, and “goes gooey” on the surface, and in the tread rubber interior as well. Under the high slip which the car generates at extraordinarily high cornering, acceleration and braking forces, the degraded surface rolls up into little balls of rubber. The fact that it is now the driver controlling these forces, instead of a “you beaut” computer, probably accentuates this because of driver variations in technique.
The cars are very light, the tyres do not deflect much, which helps to keep them running cool. The lack of deflection also diminishes the effect of the “standing wave” which is extraordinarily destructive on tyre casings. Basically, this is caused by the tyre not having sufficient time to recover its shape away from the road contact patch, before it’s back on the road again!
As the tyre wears, there is less reversion of the rubber because the interior of the tyre tread is not generating as much heat (because it has worn away), and the ‘gooey balls” may disappear, and lap times improve.
Reminds me of the old jingle, now paraphrased a little to read:-
“The tyres drove on the burning road
Going round and round like mad
Rolling it up in sticky balls.
Driver says “that’s bad””.
As for last year, the rules now state that drivers must use tyres of different compounds for at least part of the race, such variations being discernible from the white stripes painted in the tyre tread grooves. If you want to know more about the difference between “hard” and “soft” compounds, go to “all about tyres” formula 1 at www.carbonblack.com.au.
Most teams ran “hard” tyres for as long as they could because they run cooler under the conditions experienced. The rule was introduced to give team managers yet another tactical variable to control to get the best result for their car, for a particular track and conditions.
What is significant is that I did not see a tyre failure on any car during the race. Take a bow, tyre engineers!