What are the circumference and/or diameter of the large and small tetrix wheels?

What distance do each of the 1440 segments represent?

This will change depending on your drivetrain, the amount of gearing you have, the amount of resistance, etc.

test it out and determine how far it drives your robot

I believe the wheels are 3" and 4" respectively in diameter, which means 3pi and 4pi in circumference...

if you need a more absolute distance, use the sonar sensor, I have found it to be much more reliable than encoders for distance measuring, but its up to you