A few questions for the T16 experts out there.

[David Herbert]

I very much agree with Lynn.
Driving in a straight line the sprockets have the same number of teeth and are turning at the same speed. This means that the tracks are being pulled round the sprockets at the same number of links per minute. If one track is more worn/stretched than the other the pitch is longer and that track travels further so you slowly turn. If one track is more worn than the other it would often result in it having a link or two removed so that it can be tensioned but the cause of the drifting is the difference in pitch due to wear. Any difference in the number of links is incidental but indicates different pitch. As has been mentioned, if everything else is equal, different tension on each side will also cause drifting but simply because a tighter track has more drag so the vehicle will tend to drift towards that side.

David