Speedometer accuracy?

So, if the speedo was 2-3mph high to begin with (say, 67mph when the actual speed was 65), then by the end of the tires life (tire = 1" smaller in diameter) the speedometer would probably be reading 68-69mph at an actual speed of 65mph.

I'm not suggesting you don't know this- I see that you do. just illustrating a point here for those that want to better understand what's going on (

 

Since a Circumference of a 33 rather is bigger than a stock tire would that mean that the "miles" put on the truck would not be an exact number?

 

The other issue is speedometer error can and often is a different % than odometer error.

 

Correct. If you go from stock tires to 33's, your odometer will be off. In this case, moving from a smaller to larger diameter tire will result in an odometer reading slightly less than the distance you actually drove. If you drive an actual 1 mile in distance, your odometer will read less than a mile (I don't know exactly what it will read, but probably something like .92 or .94. Doesn't sound like a big deal there, but at 150k miles on a truck with 33's, your odometer might be off by a few thousand miles. This is my understanding.

 

That case I'ma upgrade to 37s