BARCELONA, Spain -- Sebastian Vettel suspects Mercedes' impressive pace in qualifying on Pirelli's softest compound is linked to changes to the tyre's tread depth for this weekend's race.
Lewis Hamilton put an end to Vettel's run of consecutive pole positions on Saturday as Mercedes took its first front-row lockout since last year's Abu Dhabi Grand Prix. The return to form came at one of the most aero-sensitive circuits on the calendar, but also after Pirelli reduced the thickness of the tread by 0.4mm on its tyres to combat overheating.
During pre-season testing at the Circuit de Catalunya, a number of teams -- most notably Mercedes -- struggled with excessive overheating and blistering on the circuit's newly-laid track surface. The new, smoother surface was resulting in minimal wear, which in turn was causing the compound to overheat through the circuit's high-speed corners. In agreement with the FIA, a decision was made to reduce the thickness of the tyres for the Spanish, French and British Grands Prix -- a decision that appears to be sparking some controversy after the first use of the thinner tread tyres.
Asked why Mercedes, which so far this season has struggled on Pirelli's softest compounds, found more performance than Ferrari on the super-soft, Vettel said: "I think it's pretty straightforward, the tyres are different. They're different for everyone so everyone needs to cope with that.
"I think it was exceptional that Mercedes was struggling in the last events as much as they were but thinner thread, basically the tyres are harder so we still have the same tyres if you look at the colours but they're harder than they're used to be. As I said, it's the same for all of us."
After making a mistake in the first corner on his first Q3 run on the super-soft, Vettel switched to the soft compound for his second run and improved his lap time with a much cleaner lap. Despite missing out on pole position by 0.132s -- a step in performance a clean lap on the super-soft should have offered over the soft -- Vettel is confident he made the right decision.
"In Q3, the first run, I locked up a little bit into Turn 1 so the first sector was already slow and I tried to get back and recover, but to really fight for pole it was not enough," he said. "I didn't get a great feeling on that tyre so I decided to ask to go back and I think it was the right call. We were very quick.
"I think overall the tyres this weekend are different. Obviously we had the change for everyone but I think they are a bit harder, so for me it was pretty straightforward as I said because I was happier with the car with that tyre.
"If it's within one tenth, one tenth and a half you always think maybe, but to be honest I was very happy with the lap until the end. We expected Mercedes to be very strong and so they were. Hats off to them and tomorrow I think it will be a close race, anything can happen really just like the last couple."