World championship rivals Jorge Lorenzo and Dani Pedrosa opted out of Friday practice for the San Marino Grand Prix after rain dashed hopes of any useful dry runs. Only 13 of the 21 riders went out on the partly dry Misano circuit with nine-time world champion Valentino Rossi managing just one careful lap before he headed back to the Ducati garage. \"On days like this it\'s almost impossible to get any feedback on the bike,\" said Honda\'s Pedrosa, who has won the last two races and trails Yamaha star Lorenzo by just 13 points in the world title race. \"Actually, we saw in both sessions that the weather was changing so quickly that the riders going out with slick tyres had to come back in because it started raining or the other way around: going out with wets and destroying them in just a few laps as it was drying up again. \"The weather forecast looks better for tomorrow and Sunday, so let\'s hope we can take advantage of tomorrow morning\'s session to find a good setting and have a good qualifying.\"