[Fixer]

Both my '86 911 and my '83 928 wear the stock original wheels/tire size and both have optimistic speedometers. Both when showing around 70 mph are actually doing around 63 - 64 mph.
This seems common with Porsche from my experience.
Doesn't this mean with an electronic speedo that my true overall miles on the cars are a percentage lower? If so, and the speedos made accurate, can the the miles be legally changed to a lower number?