Hi, I have just realized that the tracks cause some friction and load the motors, even the motors are running free (around 100mA without tracks and 400mA with tracks under 6V supply). Do you also have similar results (that is the track connections are tight, squeaky and cause friction) with the tracks?
Also due to unequal friction caused by left and right tracks, the robot does not go straight but slightly steering to one direction. Do you use some encoders or any other method to overcome the steering issue?
Edit: I figured out that the steering issue is caused by speed difference of the motors, somehow even under no load, they have quite big rpm difference, when supplied with the same voltage, even though they are both 1:298 HP metal gearmotors.