Loeb, who took his ninth victory in Germany last month, got through the Walters Arena stage just before a rain shower arrived in the hills just north of Swansea.
The Citroen driver will now have the first choice of where to run on the road through the opening day of the event on Friday.
"I made one or two small mistakes, but nothing too bad," said Loeb. "It's OK."
Solberg admitted he was comfortable with second place, but felt it could have been better if the rain hadn't arrived while he was sitting on the startline for the stage.
"Unbelievable!" he said at the finish. '"he tap was turned on when we were waiting on the line. I didn't know much about the grip on the road, it was different from when we drove the stage at shakedown this morning, so I braked a little early in a couple of places.
"The time is OK, but it doesn't matter so much for me, the only goal we have here is to win ' and, let me tell you, this car is fast."
Loeb's team-mate Mikko Hirvonen was third quickest, with Thierry Neuville impressing on his Rally GB debut with fourth quickest. Jari-Matti Latvala was fifth fastest, dropping time after he ran wide over the second jump in the stage.
Evgeny Novikov was another to suffer on a jump, landing on a rock which damaged the right-front damper.
The selection of starting positions takes place tomorrow evening in Llandudno.