We’re installing the Specialized Speedzone Wireless Computer and I want to know what the correct circumference setting should be.

The little itty-bitty manual lists a 20 X 1.8 as 1589 setting but a “1.8” is not the same as a “1-1/8.”


The circumference setting will depend on what type of tire you are running. You can consult the instruction manual we’ve put together for the Specialized brand Speedzone computer (see link below), or you can use the following method to determine what number to put in.

  1. Take a piece of string and lay it out on the floor.
  2. Take your bike, and put the front tire next to the piece of string so that the valve stem is next to the end of the string.
  3. Slowly roll the tire forward along the string, until the valve stem is back to the original position.
  4. Mark the string, and measure in millimeters (the conversion from inches to millimeters is inches x 25.4 = millimeters).
  5. Enter this number into the computer, and you are ready to go!

Remember that the Specialized brand computer has two bike settings. If you are only using the computer on one bike, be sure to set both setting to the same thing to avoid confusion later on.

We’ve put together a complete instruction manual for calibrating the Specialized brand Speedzone computer for Bike Friday-sized wheels. You can find this in our Document Library. Please refer to the link below (Instructions for setting the Speedzone wireless computer).

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