• Shimano is a Japanese company that manufacturers many components and articles of clothing for cycling, including pedals, cycling shoes, gloves and gears. A bicycle crankset comprises the front gears (the chainrings), the crank arms (the "bars" the pedals attach to), and the bottom bracket (the part of the crankset that insert into the bike frame). The FC 7800 is one of Shimano's many crankset models.
  
  

Gearing

• The FC 7800 has a double chainring. This means there are two front gears. The gearing is the number of teeth on each gear. The larger chainring for the FC 7800 is available with 50, 52, 53, 54, 55 or 56 teeth. The smaller chainring has either 39 teeth (to go with the 50, 52 or 53 ring), 42 teeth (to go with the 53, 54 or 55 ring) or 44 teeth (for the 56 ring). The large gearing on this crankset makes it most suitable for a road bike.
  
  

Crank Arm Length

• The length of the crank arms relates to your leg length -- the longer your legs are, the longer the crank arms should be. The FC 7800 has crank arms in lengths of 165, 167.5, 170, 172.5, 175, 177.5 and 180 mm.
  
  

Other Specifictions

• The bolt circle diameter (the diameter of the circle made by the bolts holding the chainrings together) for the FC 7800 is 130 mm. The chain line (the distance of movement of the chain) is 43.5 mm. Shimano recommends the CN 7801 for this crankset.