After changing tire diameters from OEM, can the Z Speedometer be re-calibrated so it correctly shows the actual mph being travelled?

 

meaning reset back to 0?

 

no, he means calibrated so different size tires will show the correct speed. I dont think anyone does that for us.

 

I want to know that too... with power programmers such as Hypertech you can recalibrate speedo with a touch of button by telling the cars computer the tire sizes. Unfortunately, they don't make programmers for Z since we run an ECU... I haven't checked yet if an ECU flash will change it. I'll try to find out on Monday by calling Jet Chips.

 

What are people doing when they change final drive? That too changes how accurate your speedometer is.

 

As far as I know I don't think anybody is doing anything once they alter their drivetrain in such a way. I think everyone just lives with it. A good thing to do might be to grab a simple GPS unit and use it as a reference. You can use it to see the actually speed and compare it to your speedo display. Just make note of the differences.