Tuning Motors

I have a Hictop I3 Prusa and have my x axis drifting to the left. The suggestion has been made that I should tune the stepper motors. I have an MKS Base V1.3 as the board and NEMA 17 stepper motors. I read up on how to change the POTS, but not quite sure what the value should be coming out of the single side of the POT. Mine are currently set at X= 0.835 v Y=0.795v Z=1.022V
Extruder = 0.87V

How can I find out what they should be?

There's an article in the wiki that explains how to find out which shunt resistors you have and a formula to calculate the Vref value accordingly.

setting a preset value will not ensure proper operation the easiest might be to write a G code script to cycle the axis 200mm forward and 200mm back and adjust the pot during movement you will then find a point where the motor moves best no studder just music too much either side the motor will stop or miss steps the driver or motor will get hotter. Each driver needs adjusting to its motor as no two motors are exactly the same