Turn the round cover with a center slot located on the back of the speedometer counterclockwise with a thin coin. Set the supplied 1.5-volt battery negative terminal down in the battery compartment opening. Twist the battery cover clockwise to lock it onto the speedometer. Set the speedometer aside.
Slide the open end of the mounting bracket over the right-hand side of the bike's handlebars. Slide a rubber shim between the mounting bracket and the handle bar if the mounting bracket sits loose on the handlebar. Tighten the mounting bracket screws with a Phillips screwdriver.
Set the sensor on the right bike fork, 4 inches up from the wheel hub. Thread two wire ties through the mounting slots of the sensor. Wrap the wire tires loosely around the right fork of the bike. Allow enough slack for the sensor to move.
Place the magnet on a spoke of the front tire. Turn the magnet-locking screw clockwise to hold it on the spoke.
Turn the wheel to align the magnet with the sensor. Move both the sensor and the magnet until they sit across from each other and have 1 millimeter of space between them. Lock the magnet in place with a Phillips screwdriver. Pull the end of each wire tire away from the fork with a pair of needle-nose pliers. Cut the excess length from each wire tie with a pair of wire cutters when the wire tires hold the sensor tight to the fork.
Secure the wire running from the sensor to the mounting bracket to the fork of the bike with the additional wire ties supplied with the speedometer.
Slide the speedometer down on the top of the mounting bracket until it snaps into place.
Multiply the diameter of the wheel by 25.4 to convert an imperial measurement to a metric number recognized by the speedometer. Multiply the converted number by 3.1416 (pi) to determine the circumference of the tire. Enter the metric number into the speedometer. For example, a 26-inch wheel multiplied by 25.4 equals 660.4. Multiply 660.4 by 3.1616 for 2074.7 or 2075.
Hold the "Left" and "Right" buttons down for two seconds. Enter the metric circumference determined earlier into the speedometer by pressing the "Left" and "Right" buttons. Press the "Left" button to set the displayed distance to miles or kilometers.
Pedal your bike to activate the speedometer.