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The peloton (from French, meaning little ball or platoon and related to the English word pellet), field, bunch or pack is the main group of riders in a road bicycle race. Riders in a group save energy by riding close (drafting or slipstreaming) near (particularly behind) other riders. The reduction in drag is dramatic; in the middle of a well-developed group it can be as much as 40%.
The term is also used to refer to professional cyclists in general.
Riding in the peloton 
The peloton travels as an integrated unit (similar in some respects to birds flying in formation) with each rider making slight adjustments in response to their adjacent riders (particularly the one in front of each). When developed, riders at the front are exposed to higher loads, and will tend to slip off the front in order to rejoin the pack farther back. With sufficient room to manoeuver, this may develop into a fluid situation where the center of the peloton appears to be pushing through its own leading edge.
The shape or formation of the peloton changes according to many factors. A strong headwind or a hard effort tends to spread-out or string-out the riders, while a slow tempo or tailwind tends to bunch up the peloton into a wider formation. Side wind forces the peloton to form into echelons in the direction of the wind. Often, the width of the road forces the peloton to form several echelons. When two or more groups of riders want to contest control of the peloton, several lines may form racing one another.
While only the riders exposed to the wind, at the front and on the windward side when there is a significant crosswind, are the ones doing most of the work, it is usually advantageous to be closer to the front of the peloton. One reason is to avoid being affected by the 'elastic band effect' in which a change in speed becomes amplified as it propagates to the back of the peloton. The rider riding behind a rider who is changing his/her speed must make the adjustment at a slightly faster rate (due to reaction time) to avoid collisions.
Moreover, being closer to the front means that the rider can react to attacks and changes in position with less effort. Gaps sometimes form in the peloton, and being closer to the front reduces the risk of getting caught in the rear group when the peloton breaks form. Also, the risk of ending up in a crash declines when nearer to the front, because the front riders have the fewest fallen riders to evade. Being at the front of the peloton means dictating the tempo to some degree, and some teams or groups of riders may prefer different speeds as part of their tactics. Being at the front of the peloton is also advantageous when initiating a breakaway.
Tactical factors also apply. Teams generally attempt to cluster their members in the peloton in order to maximize their ability to affect the pack as a whole. For instance, if a team member is currently in a breakaway in front of the peloton, it is advantageous for the remaining members to slow the peloton as much as possible in an attempt to avoid catching the breakaway. This can be particularly effective in tight turns or narrow roads, where a single team can block the progress of the pack if they are in a favorable position. A similar situation occurs at the end of the race when teams will cluster in front of their sprinter, blocking the wind as long as possible while still leaving an open path in front for the sprinter to break out near the finish line.
It is typical for large hills to split up pelotons, as the aerodynamic factors are much less important at slower climbing speeds and power-to-weight ratio is the key determinant of speed.
See also 
- Edmund Burke, High-Tech Cycling, 2003
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- Hochman, Paul (June 1, 2006). "Pack mentality". Fortune (New York City: Time Inc.). ISSN 0015-8259. Retrieved July 30, 2012. "Cut deals with the enemy, maximize liquidity, punish the welshers, and other free-market lessons of the typical bike race."
- Miller, John W. (July 23, 2010). "When the Middle of the Pack Is Good". The Wall Street Journal (New York City: Dow Jones & Company). ISSN 0099-9660. Retrieved July 30, 2012. "At Tour de France, the Peloton Shields Top Riders, but It Comes With Rules; 'Moving Community'"