[andrewsmith]

Originally Posted by Cymraeg_Atodeg

I wouldn't think you'd need to change the sensor as no matter if you are measuring in MPH or KM/H the wheel goes around at the same "speed"

But, a used UK one shouldn't cost too much, just means the bikes "mileage" would be wrong

I would do this if the setting isn't there (Strange that it isn't)
You can sometimes pick up a set cheap and if your concerned about the clock showing the correct miles, contact this firm

http://www.howmanymile.co.uk/index.html

Had a set of curvy clocks from him and they were better condition than mine