Sigma 1606 Wheel size

[Spikyho]

Hey guys, I got a DTS 1606L and I don't know what to input as my wheel size. My wheels are 28x 1 1/4 which isn't a listed size in the booklet. I measured the diameter using a tape measure and multiplied that by pi but it still seems like the cyclometer is still overestimating what a mile is. I was wondering if anyone knew what number I should input into my computer so that it will be more accurate. Thanks.

I have 2,233 as my current wheel size.

-Ryan

[Jesper64]

Hmm Sheldon Brown doesn't have your tyre size in his table (http://sheldonbrown.com/cyclecomputer-calibration.html#ccc). The best way to do it would be to lay out a measuring tape on the ground and sit on your bike and measure the distance covered in one revolution of the wheel. Starting and ending at the valve stem is probably easiest.