A bike speedometer is not only wonderful in that it tells you how fast you are going but it measures the distance you have gone. It is a wonderful tool to have that adds little weight to the bike. The following will help guide you in your efforts to install a bike speedometer to your bicycle.
Install the magnet to the spoke of the front wheel. It should be clamped at the lower end of the spoke towards the center of the wheel.
Place the sensor on the fork part of the wheel. It needs to be aligned in an area so when the wheel turns, the magnet will pass the sensor's area of scope.
Route the wire to the sensor down the fork of the bike. Do this on the outside of the wheel and secure it with the ties. Allow it to be slightly lax so that the wheel will turn but there isn't too much slack that the wire gets stuck in the wheel.
Mount the bracket that holds the speedometer on the handle bars.
Attach the wires from the sensor to the mounting bracket.
Install the battery to the computer and program it to fit your bike's specifications. You will need to measure the circumference of your front tire to do this.
Test the speedometer. Ride down a street and see what it reads. Drive the same route later by vehicle to verify the speedometer's readings.