After 114 miles of racing through Virginia's Tidewater, the first stage of the three-day Tour of America bike race was won today by less than 30 feet by Francis Castaing, one of France's fastest sprinters.

An estimated 100,000 people lined roads along the route from Virginia Beach, where the race started in fog, to just outside Williamsburg, where the race ended at 2:30 p.m., moments before heavy rain began.

All 75 racers, among the world's best cyclists, finished the 3 1/2-hour race as they began, in a tight pack.

They averaged 27 mph, with sprints at more than 40 mph, and because they ended in a bunch, all were given the same time. The times of the top three finishers were reduced by 6, 4 and 2 seconds and the winners of two sprints, held in downtown Norfolk and in Hampton, also had seconds knocked off their times.

Saturday's 80-mile race from Williamsburg to Richmond is expected to break up the pack when it encounters the race's only hills in downtown Richmond. The ultimate winner of the 284-mile race could well be determined Saturday afternoon in a 9.3-mile time trial at Richmond National Battlefield Park. There, all will race against the clock with no drafting allowed, where teammates can break the wind and pull riders along effortlessly in their slipstreams.

Castaing starts Saturday's race wearing the yellow jersey of the race leader and with an eight-second advantage--he won a two-second bonus for finishing second in one of the sprints. But those eight seconds could disappear quickly in the time trials where a 60-second difference might easily separate first- and second-place riders.

Castaing rides for the Peugeot team, whose officials were delighted today because they are the race's major sponsor. All but two of the 15 premier teams in the race have sponsors, mostly firms from Europe, where bike racing is so popular.

In today's race, Vincent Barteau of the Renault team came in second, followed by Ralf Hofeditz of Wolber and two T.I. Raleigh team members, Ad Wijnands and Leo VanVliet. No American riders finished among the top 10, although John Eustis of the Geios had the race's longest unsuccessful breakaway, a lead of about 350 yards on a solo--about 100 miles into the race. As with all of the breakaways, Eustis held up his hands in surrender and exhaustion after about 20 minutes and was absorbed into the pack.

American and French race promoters were delighted with the first stage of the race, both because of the large crowds and the accident-free race that saw all riders finish. An entourage of almost 100 cars and motorcycles surrounded the racers, weaving two and three abreast at times to race to the aid of riders with mechanical failures and flat tires. About two dozen riders had flats, which required much sprinting for them to catch up to the pack.

All cities and towns on the first day's tour welcomed the racers, except Williamsburg, which refused them entrance, apparently deeming bicycles not in keeping with its colonial image.

Saturday's 80-mile race begins at Busch Gardens, outside of town. Sunday's 80-mile race begins in Fredericksburg at noon, with racers expected to enter Washington over Memorial Bridge about 1:45 to 2 p.m., and race for about 45 minutes around the Tidal Basin, before the finish on Constitution Avenue.

The last half hour of the tour is expected to be televised by CBS Sports, before the Masters golf.