Tires: odometer, odometer reading, time sarah

Question
Hi Barry,
You may know the answer..may not.  I am building a bicycle roller racing system that gives an odometer reading on a giant display dial.  I need to have the last roller hooked up to a cable system that gives output to the odometer.  I am having trouble figuring how to make an odometer into a 500Meter dial.   My roller diameter is 4.5 inches.  The bikes used on the roller have a 42x16 gear (fixed)  with 700cx28 tires.  Do you have any advice on this matter?  Thanks a head of time, Sarah

Answer
Sarah,

If your odomter reads in miles and you want to change it to kilometer (in 1/2 km increments!)

Then divide the miles by 0.621 to get kilometers.  So the fist 500 meters occurs at 0.31 miles, the first kilometer is at 0.62 miles, 1500 meters is 0.93 miles, etc.