Changing the Gear ratios in the ECU calibration

Has anyone played with the gear ratios in the tune?
What I'm trying to accomplish is to bring the speedo closer to the GPS readings but I don't know the impact of changing a few things there (essentially the final drive ratios) for accel/decel adjustment and possibly other things that we can't control in the tune (traction control, stability program, and so on).

 

Ok, the speedo displays the readings via whatever the ABS module reports, so there is no influence at all from the gear ratios in the tune. It makes sense though, when in between gears or the clutch is pushed in the speed will still display correctly and has nothing to do with the gear ratios at this point.

 

Speedos are also historically incorrect, as is the tach from my experience. It's hard to keep an analogue gauge in check when things can change very quickly. Is there a tire size change you can make in the tune? I don't recall.

 

No, there isn't, that would have to go into the ABS control module as well and VT only handles ECU stuff.

Indeed, but the accuracy is decent and the error in the speedos is actually programmed (same for the engine RPM gauge). the OBD speed is pretty much on par with the GPS speed on the other hand.