You can measure your wheel by placing your bike on a flat surface with the valve stem on the wheel in the bottom most position or 6 o clock position. mark the floor where the valve stem is. now roll the bike forward so that the wheels gets one full revolution and the valve stem comes back to the 6 o clock position and mark the floor at the valve stem. now get a tape measure and measure the distance between your two marks. Convert this measurement to usually centimeters. that will be the number that put into your computer.
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You can measure your wheel by placing your bike on a flat surface with the valve stem on the wheel in the bottom most position or 6 o clock position. mark the floor where the valve stem is. now roll the bike forward so that the wheels gets one full revolution and the valve stem comes back to the 6 o clock position and mark the floor at the valve stem. now get a tape measure and measure the distance between your two marks. Convert this measurement to usually centimeters. that will be the number that put into your computer.
the manual can be downloaded here
Rick
Bicycle Parts and Accessories