Hi Arnie,
The top speed setting can be changed in the settings menu (accessed by holding down the up & down buttons on the power pack). Once inside the settings menu, do the following:
- Press the centre button once to select the wheel size setting
- Use the directional buttons to select between the lower (15mph) and higher (20mph) setting on the right-hand column of lights
- Press and hold the centre button to confirm the setting and exit the settings.
A full guide to the power pack settings can be found here: