My Roadster under reads by 10% but MMC says it is legal. Another feature! I fitted a GPS speedo off fleabay as belt and braces
MMC is wrong, all manufacturers are required to fit speedometers that do not under read that is why most over read by 10% it is to protect your licence. It is possible to re-calibrate your electronic speedo using the reset button I think there was a post on here once.
