STRASBOURG, FRANCE, JULY 5 -- Erich Maechler of Switzerland retained the overall lead in the Tour de France bicycle race today after Belgian riders won two short stages on solo breakaways.

Belgian Herman Frison surged after 2 1/2 miles and finished 1 minute 28 seconds ahead of the pack to win the 49-mile fourth stage from Stuttgart to Pforzheim in West Germany.

Marc Sergeant, the 1986 Belgian national champion, broke away 28 miles from the finish and held on to win the 70-mile fifth stage to Strasbourg. He finished in 2 hours 32 minutes 29 seconds -- 13 seconds ahead of the pack.

Maechler of the Carrera team retained his 44-second overall lead over compatriot Joerg Mueller. He is 55 seconds ahead of Italy's Giancarlo Perini, 1:35 ahead of Portugal's Acacio da Silva and 1:36 ahead of France's Charly Mottet.

The fifth stage began under sunny skies, with Luis Herrera of Colombia, Andy Hampsten of the United States and Raul Alcala of Mexico pulling ahead of the pack. At 32 miles, Sergeant took the lead, and at one point was four minutes ahead, riding alone on the Rhine plain.

In the fourth stage, Frison, 25, led most of the way and finished nearly 1 1/2 minutes ahead of runner-up Jean-Paul van Poppel of the Netherlands. Frison finished the distance in 1:49:23.