I need to recalibrate my speedometer. I know this question has been asked, but the only answer I've ever been able to find is, "you have the wrong size tires."

My z has been dropped 1.2? Inches in the back and the fenders have been rolled bc I'm running 20 inch wheels. I'm not even going to state my tire size bc I know they are the "wrong" size. I don't care. I like the way it looks. I like the way it rides. I like the way it handles. I'm not changing my wheels and tires.

So how do I calibrate my speedometer?

 

I used this successfully in my Z to calibrate the speedo

https://shop.12oclocklabs.com/index....&product_id=59

 

Thank you thekinn, nice to know that works.

Right know I'm going to consider this plan-b. I was really looking for a way to modify the parameters in the ecu. If it can be done.

 

The speed calculation is done via the ABS sensors, the average rotational speed is then taken and converted into a digital signal and sent over the CANBUS. To my knowledge these values cannot be modified at the PCM/ECU level since it's taking raw analog data and converting it to digital. Maybe I'm wrong, maybe this type of feature is available from an aftermarket reflash company like Uprev.
-Icer

 

Dang it looks like you're right. I downloaded the FSM which plainly states:

SPEEDOMETER
VDC/TCS/ABS control unit (with VDC system) or ABS actuator and electric unit (control unit) [without VDC
system] provides a vehicle speed signal to the unified meter and A/C amp. with CAN communication line. After
unified meter and A/C amp. received the vehicle speed signal, it changes the signal to 8 pulse signal to the
combination meter for speedometer.

The manual shows the ABS/TCS controller receives the speed signal from straight from the sensors and also says the only CONSULT2 functions for the Unified Meter and A/C Amp are self diagnostics and monitoring.

So I guess its plan-b for the win.

 

As mentioned nobody seems to have an actual calibration yet. If you are running a square wheel package you may be able to alter their signal for ABS/tcs to properly function. The g35 sedan has different rear stub , only difference is the tooth count for the sensor.

why did they do a different tooth count vs just tweeting the parameters of the ecu I don’t know. Would also have to crunch numbers and check what direction it would change your speedo