[Roccaas]

2 separate GPS systems record my actual speed (55-85 mph range) as 2 mph slower than: speedo, cruise setting, HUD, and dash computer.

I haven’t tried to compare anything under freeway speed.

Car has original 20” 2H9 package and Dunlop stiff walls, so I don’t think it’s anything to do with tire circumference.

Not a big deal, I just adjust my speed to WAZE or GPS device speed for a long cruise, but I’m guessing there’s a worn part (used to be plastic worm screws in analog cars) that can be replaced or adjusted.

Thanks