As all have already said, my 2012 speedo was
slightly optimistic from the factory.(as most all vehicles I've ever had)
Installed a PR2 190/55 and it's been close-enough to accurate for me since.
Never have tracked actual mileage vs. odometer readings though-
More on that later-
I hadn't been in years..
but I got dinged a couple weekends ago.
89 in a 55-

KSP's "moving
LASAR" doesn't discriminate I suppose...
It will only hurt a little they say... Right?

I'm just glad he didn't catch me 200 glorious miles earlier that Sunday afternoon doing something truly "jail 'n tow" worthy.

Here's to hoping the judge likes me next month...

What I don't get about the speedo/odo thing is this and this:
Doesn't matter, that is just a sending unit that sends a signal to the speedometer. If the C-14 has a digital odometer, it simply counts revolutions, and calculates mileage. If it had a digital speedometer, it would take that count and apply a time factor to get miles per hour. If it has an analog speedometer, it would then convert the result of that to an analog voltage, and send that signal to a meter movement.
The point is, that calibration of one readout does not necessarily affect the other.
Exactly right. Mechanical or digital this all applies.
One example jumps to mind. MK IV Golf TDI I used to have. The MPH read high at highway speeds but the odometer always matched up perfectly with mile markers. I plugged in Vag-Com and pulled up the vehicle speed. The speed in Vag-Com was exactly right but the displayed speed was not. That proved to me they intentionally show a slightly high displayed speed.
On that car I was able to edit the bin dump of that cluster and re-flashed the edited bin to correct the speedometer BUT it cost me odometer accuracy unfortunately. After that the speedometer was right but odometer was slightly low.
No, calibration doesn't matter... if you're the programmer or engineer.
But whether it's digital or analog, doesn't the ratio between speedo error & odometer error remain constant?
If one changes, won't the other also in direct proportion?
