F1: Practice session is tyre-incident free as Sebastian Vettel sets the pace at the German Grand Prix Sebastian Vettel is ready to take the fight to Mercedes this weekend following two incident-free practice sessions ahead of the German Grand Prix. The sport of Formula One held its collective breath prior to the two 90-minute outings at the Nurburgring in the wake of the tyre debacle that unfolded in the British Grand Prix at Silverstone last weekend. All the talk beforehand had centred on a threatened boycott of this event made by the Grand Prix Drivers' Association. That followed a meeting between the GPDA and Pirelli race director Mario Isola yesterday at the circuit. The Association made their position crystal clear, stating they would withdraw should there be a repeat of the dangerous blowouts witnessed at Silverstone, especially during the race itself. Pirelli has at least reacted quickly, and for this weekend only the cars are running on rear tyres with belts made of Kevlar - a high-strength synthetic fibre which is more resistant to punctures - as opposed to the steel previously used. Just over two hours before the start of the session the teams were also issued with a directive from FIA race director Charlie Whiting, following a request from Pirelli. Earlier this week Pirelli claimed teams' switching of the rear tyres, running with pressures too high and excessive cambers, were all part of the problem behind the failures five days ago that put the lives of drivers, fans and marshals at risk. The teams have now been asked to run their tyres at the correct pressures, with the appropriate camber, and that swapping is no longer permissible. Come the conclusion to today's practice it is a case of so far, so good, although it is worth remembering the first incident at Silverstone did not occur until Sergio Perez's blow-out on Saturday morning. After the first session Mercedes appeared to be a class apart, with Lewis Hamilton narrowly ahead of team-mate Nico Rosberg, but with nearest challenger in Mark Webber a staggering second off the pace. Come the conclusion to FP2, it was reigning triple world champion Vettel who held sway as the teams tested the quicker of the two compounds available for this race, the soft as opposed to the medium that had been used in FP1. Vettel, who has never won his home race - and more remarkably has never won a grand prix in the month of July in 12 attempts - posted a time of one minute 30.416secs in his Red Bull. Rosberg, as in FP1 behind Hamilton, was second and 0.235secs adrift, with the Briton 0.888secs down in eighth place. Sandwiched in between was the second Red Bull of Webber, Lotus duo Kimi Raikkonen and Romain Grosjean and Ferrari pair Fernando Alonso and Felipe Massa. For Alonso the session was more productive than his first in which he failed to set a time due to his car sustaining an electrical fault that kept him in the garage for all bar two installation laps. Behind Hamilton were fellow Britons Jenson Button in his McLaren and Force India's Paul Di Resta, 1.152secs and 1.381secs behind Vettel respectively. At the bottom of the timesheet was the last of the British quartet in Marussia's Max Chilton, 4.251secs down and 0.6secs behind team-mate Jules Bianchi who only managed 10 laps due to a technical problem.