CATEYE KNOWLEDGEBASE :: My tire size is not listed on the chart in the manual. How do I determine my calibration number?

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My tire size is not listed on the chart in the manual. How do I determine my calibration number?

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To determine the most accurate calibration number for your application (tire choice, body weight, etc.), or if your tire size is not listed in the chart, perform a ‘tire roll out’.

To do a tire roll out:
1. Mark a spot on the floor, and line up the tube’s valve stem with it. You’ll want to choose the wheel that the computer’s sensor is being run on.

2. Running the usual tire pressure and with the rider’s weight on the bike, roll the tire out one full revolution. When the valve stem comes back around to the ground, make a second mark on the floor. Measure the distance on the floor from point to point.

NOTE: This is often best performed parallel to a wall, to ensure the roll out procedure is done in a straight line.

3. Record this number in cm if your computer requires a 3-digit calibration # (or multiply inches by 2.54 for cm). Record this number in mm if your computer requires a 4-digit calibration # (or multiply inches by 25.4 for mm).

4. Enter this number in your computer for your wheel circumference.