Ersatz Fahrrad Computer durch Uno

Habe folgenden Code:

// include the library code:
#define LCD_WIDTH 16                    //Anzahl Spalten des Display (16)
#define LCD_HEIGHT 2                    //Anzahl Zeilen des Display (2)

#include <LiquidCrystal.h>
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);

int reedPin = 1;    //analog input, but could also be digital
int circleNum = 0;
float wheelDiameter = 18;
float wheelC = 3.14 * wheelDiameter;
float kilometers = 0;
float speedometer = 0;
float KPH = 0;
int reedTime;
int reedTimeDelta;
boolean reedOn = false;

void setup(){
  Serial.begin(9600);
  reedTime = millis();
}

void loop(){
  
  checkReed();
  getSpeed();
  }

void checkReed(){
  int r = analogRead(reedPin);
  if(r > 10 && reedOn == false){
    reedOn = true;
    reedTimeDelta = millis() - reedTime;
    reedTime = millis();
    circleNum++;
   
   //prints all metrics when magnet passes switch
    printAll();
  }
  else if (r < 10 && reedOn){
    reedOn = false;
  }
}

void getSpeed(){
  speedometer = wheelC/reedTimeDelta;
  //MPH = speedometer * 22.369; 
  KPH = speedometer * 36; 
}

void printAll(){
  lcd.begin(LCD_WIDTH, LCD_HEIGHT,2);
  lcd.setCursor(0, 0);
  lcd.print("Kilometer");
  lcd.setCursor(0, 1);
  lcd.print(KPH, 2);
}

Funktioniert auch, nur gehen die Kilometer nach Radstillstand nicht auf Null. Es wird die letzte Geschwindigkeit angezeigt. Was bitte kann man denn da machen?

Micky