Speedometer accuracy

So, when I switch the Rugged Fails with the 265/75-16 (1" taller tire), my speedo will slow and be close to right on, but my odo will begin to read less miles than I actually travel?

 

my MSD dashhawk reads a few MPH faster than the OE speedo. so, considering the OBDII standard signal for the VSS is being interpreted by my dashhawk as a few MPH faster, i'd imagine the ODO is going to be racking up miles a few ticks faster than the speedo will show, since the ODO is probably interpreting the VSS signal just like my dashhawk, as opposed to the slower means in which the speedometer is indicating it.

initially i thought the ODO rolling was directly tied to the speedo spinning but i don't believe that to be true.

 

Correct.