A peg is a long
cylendrical object protruding from the side of a
BMX bike. Pegs are made from
plastic,
steel or
aluminum depending on it's intended use. Plastic is not
commonly used due to it's weakness, but plastic pegs are still occasionally
included on
low-end consumer bikes. Steel is used for
street and
ramp riding, they are normally 3.5"-5" long and are from 2"-3" in diameter. Steel pegs are also normally very
smooth, or have only a few slight
grooves in them, this is to allow for a
slicker grinding surface. Aluminum pegs are used mainly for
flatland riding and are normally much wider then street pegs, to provide a more
comfortable surface to stand on. They are usually
knurled or
treaded to provide better grip for your shoes. There are also now
hybrid pegs which consist of an aluminum
core with a
steel sleve pressed over it. This is to reduce weight while maintaining strength.
Pegs were first developed at the start of freestyle riding in the 70s. They were plastic rectangular platforms which were attached to forks half way down and were used in flatland to stand on during tricks. They were often flip-up pegs, which could be folded up to align with the fork. Before long, pegs moved down to the axles of the wheels. They were normally threaded and would tighten down directly onto the axle. Unfortunately this design was weak, and caused axles to bend. Pegs then became simply tubes welded onto thick washers, and a nut was tightened down inside the peg onto the axle to hold it in place. This was a much stronger design and is what is used today.
The most common peg configurations are two pegs on the same side of the bike, one in front and one in back, or full pegs, with a peg on both sides of both wheels. There are also some odd configurations of pegs to be found, one of them is having 6 pegs, two on both wheels, but instead of having cranks in the bottom bracket of the bike, there are two pegs coming out of that also. This is generally used for flatland only riding, as it is hard to get speed without pedaling.
Another feature that some pegs have now are anti-roll pins, or washers. Usually just a small rod welded onto the inside of the peg, but sometimes inter-locking washer systems, these are designed to keep the peg from spinning while grinding on it. It can be usefull, but it also allows your peg to come loose without being noticable, and then the axle is subjected to the possibility of bending or snapping.
While pegs might seem like a simple thing, they have come a long way, and are used in many ways for many types of riding.