After the stand-off in Spa over the way Red Bull were using the Pirelli tyres beyond the manufacturer’s recommended limits, here at Monza Pirelli have got tough, setting lower than expected limits, which potentially gives Red Bull and others a headache.
The issue revolves around camber angle, the degree to which the tyres lean inwards at the top, relative to the bottom. Pirelli sets a recommended camber angle at each Grand Prix. Normally with plenty of dry running in practice they can evaluate their limits and set them appropriately for the race. However for some time they have been uneasy that Red Bull and others were pushing beyond the limits. The teams do this to help get heat into the tyres and to improve front grip on turn-in to corners. But Pirelli say they set the camber limits for safety reasons.
In Spa the matter came to a head when practice was wet and then in qualifying several teams experienced severe blistering, with Red Bull the most extreme. Mark Webber had to stop after just three laps of the race, Sebastian Vettel after five.
What happened then is very interesting and is the untold story behind Vettel’s Spa victory.
When Webber stopped early, the engineers immediately cut open the tyre to see if the blistering had been likely to reach the point at which it threatened the integrity of the tyre. Was a failure imminent?
Quick analysis showed that the blistering was moving towards the outside, unlike Vettel’s and others’ tyres. This was communicated immediately to the strategists working on Vettel’s race and then formed the basis of how he planned the race, opting to do a long third stint on the soft tyre. It won him the race and is a great example of the kind of calm, winning teamwork they are exhibiting this season. They had the confidence to do that because of analysis of Webber’s “test” tyre.
Back to this weekend, Pirelli have set the camber limits at 3.25 degrees, which is lower than was being mooted following Spa. There had been talk of 3.5 degrees. This means that for some teams, there will be a little less grip on turn-in, with the possibility of some understeer.
But it will also be tougher for some to get heat into the tyres. Pirelli has brought a special batch of soft tyres with thinner treads. This is to avoid blistering with the very high wheel rotation speeds here at Monza. Blistering has always been an issue at Monza. It’s normally the rear tyres that suffer the most here.
The medium tyre has fewer problems with blistering and is there as a fall-back in the race, as Webber found to his relief in Spa.
“I’m sure that Pirelli will see how it is after Friday practice and review,” said Lewis Hamilton this evening. “But it will be interesting; understeer could be an issue for some people.”
What is perhaps not appreciated by outsiders is the huge increase in downforce from the floor this year – and therefore loading on the tyres – due to the blown diffusers. It’s some 15-20% higher than last year, far more than Pirelli could have expected when they designed and engineered the tyres for this year. Luckily the construction is quite conservative and can handle it.
Next year blown diffusers will be banned, so the downforce levels will drop significantly.