Red Bull Racing driver Sebastian Vettel was the fastest man on track during the final day of testing at the Circuit de Catalunya at Barcelona. Vettel was faster than Toro Rosso drivers Sebastien Bourdais and Sebastien Buemi.
I guess maybe it's different if you measure whilst the tyre is running, but I've always understood that surface tyre temps aren't actually that useful - it's much better to probe to the core of the tyre.
To my mind, this tool is used to measure the deformation of the tire at a certain speed. Don't forget it was the main problem for Renault when they had to leave the Michelin tires to use the common Bridgestone : those ones modified the aerodynamic flow while the Michelin did not.