The aerodynamics of drafting in bicycle riding and racing are such that any rider in a slipstream can save a great deal of energy expended as opposed to riding alone and in the wind. It is from this one basic fact that most (if not all) bicycle racing strategy flows:
A drafting bike racer will keep his front wheel dangerously close to the rear wheel of the rider in front of him – only 6 inches or so to be most effective. Scientists have demonstrated that a racer riding in another’s slipstream will expend 30 to 40% less energy than the rider in front. That’s a lot of energy over a 3-hour bike race, and it obviously would give a huge edge to the drafting rider, come the finishing sprint. In fact, the power of drafting underlies most of the tactics and strategies of bicycle racing.
In a bike ride or a race, the group (called the Peleton) affords most riders involved almost a bubble sans harsh wind resistance; it is almost surreal to be racing at 30 mph and feel as though you are just gliding and peddling effortlessly.
Leveraging this principle, racers will break away from or go "off the front" of the main peleton -- in a small group -- and work together in what is called a rotating pace line to gain distance and possibly afford themselves a better chance at winning the race. Of course, the group dynamics of such a breakaway disintegrate when the finish line approaches. Similarly, the main peleton, not wanting this to happen, works harder to bridge the gap and and/or reel in any such breaks.
Even though it seems like chaos, there's subtle forces at work in the group chasing down a break. Somehow, most of the riders at the front take a turn in the wind blocking its effects from those behind and then, when tired, they retire to let others take their turn. It's called "taking a pull" but even that is suffused with strategy. For example, if you have a team mate in the break away group up the road, maybe you don't peddle as fast at the front, essentially retarding the effort of the peleton to catch the break. You can do this subtly or aggressively, the latter being referred to as "blocking".
Another type of slip stream drafting is called a "lead out" -- that's pronounced "leed" not "led" (as in "get the lead out") -- and is almost like a slingshot effect where one a good sprinter uses a fast rider in front of him as kind of a booster or first stage and then rockets past him to the sprint.
I could go on endlessly about this, but you get the idea.
Now, for those who don't know, the Tour de France is a stage race. That is, it is a series of individual races held over a three week's time in July. All of the races do not occur entirely in France, by the way, but rather have been held in neighboring countries such as Belgium, Luxembourg, and even in England. There was talk of holding the prologue stage -- a short time trial that starts the Tour -- in the U.S. but this madness died away rather quickly when the logistics were considered.
Also, certain rules of timing come into play here as well that further dictate strategy and tactics. Riders in any large group crossing the finish line are awarded the same time and rules infractions -- dangerous bike handling or overly aggressive behavior -- can have time penalties assigned to the offending rider. One rider was dropped from the tour this year for attempting to ride a fellow sprinter into the pylons lining the final 500 meters of a stage.
The GC leader in the tour, of course wears the Maillot Juane (yellow jersey) and is a target on each and every stage. There are other subtleties and nuances as well: in addition to the GC, there is the points winner (green jersey or Maillot Vert) for those collecting the most sprint points, Maillot Blanc (white jersey) for the best new rider, and Maillot à pois rouges (polka dot jersey) for best climber. So, basically each stage is a scramble for glory in a number of different categories and you need a score card to determine, as the old limerick about the gay guy arguing with the lesbian, about "who has the right to do what, and with which, and to whom".
Add to this competition for teams (each pro team has nine riders) and the fact that the tour is one big commercial caravan around France and you end up with a month-long cycling carnival at whose center is an athletic endeavor where the leader's fortunes could turn in an instant. Mix in the A-type personalities of competitive cyclists, the hype, and prizes and prestige involved in winning the whole race or merely a stage, and you have a potent recipe for melodrama at its best.
It is a month of General Hospital episodes played out at 50 kilometers per hour. Like my friend calls it:
"As the Wheel Turns"