Originally Posted by
Johnskers
My problem with getting a different sized tire is that the speed change is progressive where as the Micra's speedo is constantly higher(poster earlier in this thread by "MetroMPG") Also, everybody is saying that the distance the ecu is calculating is correct, so wouldn't changing tire size affect this. (Honestly I like that it reads 4kph over, it will save me tickets in the long run) But i will speak to my service manager about it.
I can only speak for my Micra. The odometer and speedo are both way off.
I would think that the ECU calculates the speed and distance traveled, using info from a single data point... somewhere aft of the transmission output shaft. Some guys are saying that they can be calibrated separately, but I'm not sure of that.
Radar evidence puts me at 54kph when the speedo reads 60kph. Trucks limited to 105kph blow by me like I'm going backwards when my speedo reads 100kph. My commute to work increased about 4km (i'm about an 80km commute) even though a considerable short cut opened up right at the same time I switched to the Micra. ( I have not measured the short cut, but it would be over 1km and probably closer to 2km). All my numbers are approximate, except for the radar.
A taller tire will go towards fixing the speedo and the odo (as it has on my car), and hopefully the dealer can re calibrate to make up the difference and for those wanting to keep stock tire size.
Ten Grand Tin Can
__________________________________________
View my fuel log 2015 Micra S manual: 5.3 L/100 km ... 53.2 mpg (Imp) ... 18.8 km/L ... 44.3 mpg (US) ...