SPA-FRANCORCHAMPS, Belgium -- Tyre management is likely to be the key to success at the Belgian Grand Prix after teams and drivers have struggled to cope with the unusually high tyre pressures prescribed by Pirelli this weekend.
Pirelli prescribes the tyre pressures ahead of each grand prix weekend and since two tyre failures at the Belgian Grand Prix last year, those numbers have been enforced by the FIA to ensure tyres are not pushed beyond their limit. This weekend the pressures are set at 23.5 PSI at the front and 22 PSI at the rear, but several drivers have complained they are too high, resulting in overheating, blistering and high levels of performance degradation.
"The pressures are unbelievably high," McLaren driver Jenson Button said. "It's amazing what we have to do to get these tyres in the working window. If you push on your outlap they are done by Turn 3 with blistering and overheating. What we have to do is crazy and I've never had to do this before in my F1 career.
"It's the pressures, obviously it's not helped by the temperatures, but we go to hot countries and I think Pirelli know that. It's a shame we are so high with the pressures because we are in a position at the moment where you can't push the car, you are just rolling around the whole time with the tyre."
Pirelli motorsport boss Paul Hembery said the unusually high temperatures at Spa-Francorchamps this weekend -- which have been around 32-35C, but were slightly cooler on race day morning -- are also contributing to the high degradation levels.
"The high track temperatures have increased the wear and degradation rates on a circuit that is already very demanding on tyres," he said. "We're expecting two or three pit stops per car, depending on degradation rates."
But Williams head of vehicle performance, Rob Smedley, said the pressures are the key contributing factor to degradation, regardless of temperatures.
"If there's any talk about the tyres there will be certain quarters that come here and defend it because it's unnaturally hot, but we shouldn't hide behind the fact that running 24 PSI round here gives us massive degradation," he said. "The modulus [tyre compound choices] is slightly on the more aggressive side, but the pressures are the principle reasons why we are having high degradation. It's a simple fact and we shouldn't hide behind anything that might help out certain quarters.
"We were upwards of trying to bleed off 30 seconds on the outlap [during qualifying], which is not normal at all. But with the very high starting pressures that we are obliged to run, it means that on track, even on one timed lap, we are still well above 22 PSI and on the longer runs, without management, they can get up to 24 or 25, as we saw in Firday practice.
"It's an area of the tyre we don't usually explore. For us we are desperate to try and get the pressures down because there is more performance and we understand the tyres more at those pressures, so we can act accordingly. It's a problem for all of us."
Lewis Hamilton has already made clear that he expects to struggle with the tyres as he comes through the field from 21st on the grid, with the challenge of following in another car's dirty air making tyre management all the more difficult. Two or three stop strategies have been predicted by Pirelli, but Hamilton could have an ace up his sleeve after saving three sets of brand new soft tyres for the race -- a compound designed to work in high temperatures, unlike the super-soft and mediums.
Meanwhile, team-mate Nico Rosberg on pole position will start on the soft tyres and has two sets of new medium compound tyres available for the race, as well as one fresh set of softs. The two Ferraris and Daniel Ricciardo will also start the race on softs, but the rest of the top ten must use the super-soft, which is only expected to last a handful of laps, after using it to set their fastest time in Q2.