Feature F1 Unlocked
TECH TUESDAY: The challenge Austin presents for Red Bull – and the sliver of hope it gives McLaren and Ferrari
Although the tyres are unlikely to make headlines around Austin this weekend in the way they did at Qatar last time out, they will probably be every bit as crucial in determining the order.
The layout and surface of the Circuit of The Americas (COTA) places a very specific combination of demands upon the tyres – and some cars tend to resolve the conflict of these demands better than others.
Because the first sector features the very fast interconnected Esses (Turns 3-4-5-6) – a section of track where the tyres are under extreme and sustained load with no straight in between in which they can cool – much of the tyre’s energy is already spent early in the lap.
Although Sector 2 (which begins just before Turn 7 and ends just after the tight Turn 12 at the end of the back straight) gives them something of a breather, they are required to support sustained high loads again through the long parabolica of Turns 16-17-18 in Sector 3, meaning the rears in particular tend to be too hot for ultimate traction out of the tight final two turns, 19 and 20.
Taking everything from the tyres through the Esses of Sector 1 will compromise their performance through Sector 3. There is a trade-off to be made, and where that optimum balancing point lies will vary from car to car. But that’s just the start of the tyre management complexities here.
Even over a single lap, there are further complications. Getting the front tyres up to optimum temperature for the beginning of the lap is not straightforward here; in not over-working the rears on the preparation lap, it is very easy to arrive at Turn 1 with under-temperature fronts.
There is a big difference in how the rubber behaves according to its temperature. Elastomers are the molecular bonds between the polymers of the rubber which give it its elastic quality. When unstressed, these bonds are clumped in a sort of ‘meatball’ formation within the rubber. But when the tyre is put under load they stretch into more of a spaghetti formation before then returning to ‘meatball’ when the loads are released.
If the tyre is too cold and brittle, those bonds tend to be very short before they snap, so the tyre does not give much resistance to the load being applied. If the rubber is too hot, those elastomers stretch too much and do not return to the ‘meatball’ formation, again resulting in less than optimum resistance to the load.
There is an ideal window of tyre temperature where the tread’s rubber is just rigid enough to maximise the load being applied and where the tyre’s core has enough give to support the tread (so that the tread is not trying to absorb the entire load). Getting both front and rear tyres to that optimum point simultaneously is no simple matter, especially with a layout like that of COTA.
Pirelli’s chief engineer Simone Berra last year gave some further insight into this particular COTA challenge. "In general here the difficulty is doing the out-lap to have well-balanced front and rear axles – to have performance from both axles," he said.
"It’s always a matter not to overheat the rear but getting good temperature in the front tyres on the first timed lap into Turn 1… a new tyre gives better peak grip but it’s more difficult to balance the requirements of the two axles on the prep lap. When you use a scrubbed tyre, then the peak is gone and with less peakiness you can manage better the prep lap and sometimes be slightly faster.
"But the best theoretical solution is always new tyres with a good prep lap, managing the last sector, then go. You especially have to control the rear temperature."
Last year, Ferrari were able to find that balance on new soft tyres, but Red Bull had to resort to a scrubbed set, with the result that Carlos Sainz was on pole ahead of team mate Charles Leclerc, with Max Verstappen only third on the grid.
We have seen something similar at Monaco for the last two years, with the Red Bull needing two preparation laps to get that front-rear temperature balance and therefore surrendering peak grip to rival cars – the Ferraris in ’22, Fernando Alonso’s Aston Martin this year.
That slight reluctance of the Red Bull to quickly generate front tyre temperature is probably partly to do with its extreme anti-dive front suspension geometry. This helps give fantastic control of the car’s aerodynamic platform.
With less variation than other cars in its pitch angle between flat-out running on the straight and under heavy braking, the aerodynamic map of the car can be made more extreme and the car can be run lower, inducing greater downforce.
But part and parcel of that reduced amount of dive under braking is that there is less energy being fed under braking into the front tyres and they therefore take longer to reach working temperature.
But that one downside of the Red Bull’s concept in qualifying will often pay back in the race, because once the front tyres have reached their working temperature after a couple of laps, the anti-dive geometry is actually helping to minimise the stress upon them. Therefore the Red Bull very often has a greater resistance to front tyre deg than rival cars.
We have many times this year seen Verstappen and Red Bull prevail despite that underlying difficulty in equalising tyre temperatures between the two axles over a qualifying lap. COTA represents one of the more difficult challenges for them in accessing their full potential.
That might give, at least, a sliver of hope to McLaren and Ferrari, especially given the limited scope for set-up changes offered by the Sprint format.