my speedo is NOT 10% off
so as most of you know by now, if you own a production cruiser, your speedometer is actually reading out about 10% lower than your actual speed. at least at speeds above 50mph. but i've always suspected that mine was more 'accurate', at least when i found this out. and, i don't know if this has any bearing, but i started taking notice after i changed out my exhaust, intake, and added a fms. i haven't changed out my pulleys or gearing or anything like that. my rear tire is a 180 whereas the stock tire was a 170 with the same aspect ratio.
i've previously run through those speed signs that tell you your speed at various speeds and then looked down at my speedometer and either be right on the button or just a couple mph off. usually this has been at slower speeds like 30-50mph. maybe it was human error, maybe that sign was off, maybe our speedos are dead-on at those speeds, or whatever, but it wasn't very scientific conclusions.
then i got my first speeding ticket on a motorcycle in 2014. i was clocked at about 70mph and i KNOW i wasn't going much faster than that, if at all (i was either in a 55mph or 60mph zone). then this past weekend i went through multiple speed signs with the digital outputs. with my speedo reading at or very near 70mph, the signs would display 67 or 69. again, not a scientific reading, but very telling. and if my speedo were truly 10% off as everyone else's seems to be, my needle would have needed to be near 75 to get those readings, right? is anyone else's speedo more accurate than others? does my bigger tire make the difference?