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Instructions for a Sigma Bicycle Computer

Updated February 21, 2017

Bike computers allow cyclists the ability to measure trip distance, speed and time. They have an odometer, plus measure time of day, maximum speed and average speed. All functions are displayed on a monitor attached to your handlebars. The display readings are constant and will automatically start by themselves. But if your battery goes dead and you have to replace it, you need to manually reset your wheel size. Accurate wheel size is vital to your bike's calculations. If you lose your manual you can still reset your wheel size by measuring your wheel and entering the data into the computer.

Hold the computer in your hands. Check your display; click the button on the front of the computer once or twice until the display reads, "bike one."

Turn the computer over. Press the small grey button for five seconds until the word "language" is displayed. It will give you a choice; choose English by pushing the button on the front of the computer while the word English is flashing.

Push the small grey button on the back of the computer to switch the reading to wheel size.

Measure your front tire from the top of the tire, to the bottom of the tire where it touches the ground. Using that measurement do these calculations, measurement x 25.4 x 3.14. Now divide that measurement by 1.61 to get your wheel size. You will get a four digit number approximately 1,287 for most mountain and road bikes. This is the code number that you need to enter into the computer.

Press the top button to advance to the first number flashing on your display. Press the bottom button to make the second digit flash. Press the top button to advance to the next code number. Press the bottom button to make the third digit flash, press the top button to advance the third number. Press the bottom button to make the fourth digit flash. Press the top button to advance to the calculated number.

Press the indented set button with the tip of a ballpoint pen on the right side of the small grey button on the back to lock in the wheel size. Your computer is calibrated for your bike and ready to go.

Things You'll Need

  • Tape measure
  • Ballpoint pen
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About the Author

Specializing in hardwood furniture, trim carpentry, cabinets, home improvement and architectural millwork, Wade Shaddy has worked in homebuilding since 1972. Shaddy has also worked as a newspaper reporter and writer, and as a contributing writer for Bicycling Magazine. Shaddy began publishing in various magazines in 1992, and published a novel, “Dark Canyon,” in 2008.