It must be enormously frustrating that MMC can't sort this out, as they simply _must_ have access to the recalibration screens in the dash software. They offer the car with 15, 16 or 18 inch wheels, so it's inconceivable that they would do this if they couldn't program the dash correctly.
What car is the dash originally from, by the way? There are loads of YouTube videos on recalibrating Ford speedos, I can understand why MMC don't want customers fiddling about themselves, but it indicates that it's possible to do...
