The only necessary adjustment of the wheel diameter is made through a small hole on the left side with a paperclip. Please do not exert great pressure!
In setting mode the decimal points are indicating and in delivery status a diameter of 41cm is displayed. Each time you press the button, the value is increased by 1cm. For saving the value the button must be pressed for 3 seconds and when you release the display blinks and the value is stored. While pressing the button and switching on the ignition the diameter is again set to 41cm.