World Championship leader Casey Stoner dominated Friday's first free practice session for the US MotoGP at Laguna Seca.
With air temperatures of only 16 degrees, riders were naturally cautious not to add to the long list of cold tyre crashes when the session opened.
Home star Nicky Hayden was bravest in the early stages, before Repsol Honda rider Stoner took over at the top.
Stoner, who set a circuit record of 1min 21.376sec on his way to second behind Jorge Lorenzo in last year's race, then remained in charge (courtesy of his sixth of 19 laps) right to the chequered flag.
Team-mate Dani Pedrosa, who took his second win of the year - and first since fracturing his collarbone at Le Mans - last Sunday in Germany, tipped off his RCV at low speed when he ran into the turn two gravel after 15 minutes.
The Spaniard recovered to finish in second place, 0.102sec from Stoner, having set his best time on his last lap of the morning.
Reigning world champion Lorenzo, who has cut Stoner's points lead to 15 points, took third place for Yamaha (+0.120sec), with team-mate Ben Spies the top American in fourth - but over half a second from Stoner.
Factory RCV mounted Italians Andrea Dovizioso (Repsol) and Marco Simoncelli (Gresini) were fifth (+0.611sec) and sixth (+0.910sec) with Hayden slipping to seventh (+0.997sec), but still the lead Ducati.
Hayden, who took his most recent MotoGP win at Laguna Seca 2006, and team-mate Valentino Rossi each have one GP11 and one GP11.1 motorcycle at their disposal this weekend.
Rossi has used the GP11.1 for the last three rounds, but has failed to find a clear gain - despite promising tests when fitted with next year's 1000cc engine.
Hayden made his debut with the GP11.1 this morning, but is thought to have set his best lap with the GP11.
Eighth place and top satellite bike rider was Monster Yamaha Tech 3's Colin Edwards in eighth (+1.159sec), with Rossi ninth (+1.167sec) and Suzuki's Alvaro Bautista tenth (+1.229sec).