Bicycle speedometers are a relatively inexpensive way to upgrade your cycling experience. They can help you progress as a cyclist or just serve as another way to make riding your bike fun by tracking variables like speed and miles travelled. Operating most bicycle speedometers, also known as cyclecomputers, is a snap. Resetting the computer is among the easiest of tasks, while setting tire size can present a slight challenge.
Setting Tire Size
Get into your bike speedometer's set-up menu. Details for doing this will vary from computer to computer. Once in the menu, find your way to tire size setting.
Enter either your tire size, found on your tire's sidewall (e.g., "26 x 1.95" or "700 x 28"), or the code that represents your tire size. Which option you need, again, depends on the make and model of your speedometer. For example, most specialized computers allow you to choose from one of 14 tire sizes that are pre-programmed. A CatEye computer is different in that it include codes in its owner's manual that coincide with most tire sizes. Your tire size is set once you've entered this information.
In cases where you don't know your tire size or you desire more precision, manually set your tire size. Situate your bike on a flat and clear space.
Mark the floor and your tire exactly where the two meet.
Move your bike forward far enough to complete one revolution on your wheel. Mark the floor where the revolution ends.
Measure the distance from mark to mark. How you take this measurement (e.g., in inches, in millimeters, etc.) and what you do with this number (input it into your computer or consult the owner's manual for a code that goes with it) will, once again, depend on the make and model of your computer. Return to step two and input this number in the tire size section of your speedometer's settings menu.