1.  Field of the Invention
Generally speaking, the invention relates to bicycles, and more particularly, to apparatus, methods, and kits for single-speed bicycle conversion. 
2.  Description of Related Art
Bicycles are two-wheeled, human-powered land vehicles that use a chain and sprocket drive train to transmit power between a pedal-actuated crank and a driven wheel.  Many bicycles are “multiple speed” in that they have sets of closely spaced sprockets or gears coupled to the driven wheel and a mechanism, such as a derailleur, for moving the chain between the various gears.  The variable gearing ratios provided by the multiple, selectable gears allow the bicyclist to pedal at a comfortable, efficient speed while the driven wheel moves at a corresponding speed that can be adapted to suit the terrain. 
Some bicycles are “single speed” in that they have only one sprocket or gear on the driven wheel, and thus, do not provide a variable gearing ratio.  Single speed bicycles often require more work or effort from the cyclist, who must pedal without the assistance of variable gearing ratios.  However, single speed bicycles have become particularly popular among some enthusiasts, who value them for their simplicity and fitness potential. 
Although dedicated single speed bicycles are made and sold, one of the least expensive options for obtaining a single speed bicycle is to convert an existing multiple speed bicycle to single speed.  To do so, one removes the set or “cassette” of sprockets or gears that are connected to the hub of the driven wheel and replaces that set of gears with a single gear.  Traditionally, this process is performed using a single speed conversion kit that includes a gear and a number of spacers.  The spacers slide onto the hub on either side of the gear, and the kit usually includes some sort of locking mechanism to lock spacers and gear onto the hub.  Once in position, the spacers define the lateral position of the gear along the hub and help to retain it in that position. 
There are several notable disadvantages to the use of the traditional single speed conversion kits described above.  First, the lateral position of the gear on the hub can only be set in increments defined by the width of the spacers—it cannot be positioned at an arbitrary location on the hub.  Second, the kits are cumbersome with their multiple parts.  Third, once the gear is installed, the user may find that the position of the gear should be changed slightly for optimum chain alignment.  In that case, the user must disassemble the wheel assembly, remove all of the spacers, and begin again.