Stock tire size is either 265/70r16 or 245/75R16. I verified my speedometer with GPS. Also had Toyota verify my speedometer. They told me it reads 5mph faster than what you are really going. When I put on the 265/75R16 on which I believe is almost a inch taller corrected the speedometer.
Verify your speedo now and you will most likely see it reads 5mph more than what you are really going. Going to the taller tire will actually bring that to almost dead on
What size are you goin to? Most tacomas read 5mph faster than they are really going stock. After I put on my 265/75-16's on I'm now 2mph off actual speed according to GPS