Tour de France riders can look forward to another miserable day in the saddle on Friday with more rain and strong winds forecast for the 196-km sixth stage to Angers.

Through much of the first week riders have faced difficult and often treacherous conditions as driving rain turned roads as slippery as ice skating rinks, resulting in a string of crashes.

American Lance Armstrong, who is chasing an unprecedented sixth Tour crown, and his U.S. Postal team have largely stayed out of trouble in the opening stages and on Friday will once again be content to cautiously bide their time in the main pack.

Race doctors treated 11 riders on Thursday and many more went down in the wet conditions, with two pile-ups scattering the main field.

Despite the rain and dark clouds, however, it will be a bright start to the day for French fans with Thomas Voeckler slipping into the leader's yellow jersey.

The Frenchman took over top spot in the overall classification from Armstrong when he was among a breakaway group of five riders to come home with a 12 minute lead over the main bunch on Thursday.

Armstrong sits sixth in the overall rankings, nine minutes, 35 seconds behind.