Speedometer calibration questions

[mp3deviant721]

Aight guys. I am going from a 225/70/14 to a 235/75/15. I wanna keep my 3.08 gears in the diff. But what I figured out using calculators from the "Tech Library" is that I would need a 15.538 gear. I rounded that up to 16. Is there anyway I could figure out the margin of error and actual speed I would be traveling with that speedo gear and tire? Do you guys think that half a tooth will make much of a difference? My daily drive to school and work usually consist of roads that have police patrolling them so I want my speedo to be as close as possible. Thanks guys.

 

[mp3deviant721]

Bump

 

[mp3deviant721]

Nobody? Anybody? No math geniuses here?

 

[Flightnerd]

Just do it, then drive with a GPS at different speeds to figure out your true ground speed. Either remember the correction or make a little correction card by your speedo.