Inaccurate speedometer

[gj3ny]

My 2002 has stock wheels but is no longer running on the original tires. The tires are of stock size. The speedometer reads between 3-4 mph over the actual speed.

I also wondered if there was something I could do to show actual speed. So I plugged in my OBD reader a scan gauge 2 and found out that the car actually knows what the accurate speed is, so your odometer is correct but some how our speedometers actively convert the speed a percentage up.

I now run my smart phone with the app "torque" and GPS speed shown.