3 MPH faster is typical for this bike. You cannot recalibrate, either. Tire wear makes no perceptible difference. Write a letter to Yamaha's consigliari's for the reason... FWIW, outside of my Road King's speedo, which was dead nuts on, this is the most accurate speedo I've ever owned as far as bikes go...
That's because a Road King doesn't go fast enough to have speedo error
Sorry, I had a guy walk past my 06 today, looked at it, said "If it ain't a Harley, it ain't noth'n. And walked away. I said after him "A Harley is kind of like a motorcycle, only much slower!" He game me a pissed off look and said his was "Pretty fast." I said yeah, maybe fast for an antique. He got mad and left then.
I just get sick and tired of guys look down their noses at other bikes saying they have Harleys, then getting into their girlfriends Toyotas and driving off.