Dear all,

I have just change the final gear ratio to 4.2 from the original 3.9 in the aveo manual gear box. My question is, will the speedometer's speed be affected? I was travelling at 80km/h today (seen in my speedo) but when I drive towards a honda civic with a digital speedo beside me, I travel same speed as him, but his meter showed 87km/h. This makes me worry as my country has a lot of speed camera and I am unsure of the speed I am travelling now. Does a Scangauge help? It can extract the speed from the OBDII port direct from ECU.

Where is the speed sensor located on the aveo? How does it works? And my wheels are 205/40/ZR17. Which ithe overall diameter is slightly bigger (abt 2%) compared to the stock 155/80/R13 it came with when I bought the car.

Anyone have a way to caliberate the speedo?