The others have pointed out one thing.   Another which we have found is certain situations where the ground is worked up very loose.   I hate running the Cat's on fields which have been disked deep.  All day long you are climbing up on top of the loose dirt.  You climb up until you get more weight up then the soft surface can support, then you sink back in again and the process starts over.   It's like being in a boat on a rough lake.   The same conditions in our 4wd are usually reasonably smooth, although I have seen occasions where they behave similarly.  Add slight ridges from the disk makes it even worse.    The best answer is to not use the stinking disk. 

On the other hand, go into a field with old rows, or a field which has been chisel plowed without a harrow, or any similar corrogated surface and the tracks can run at any angle other then a very shallow one and you won't even notice them.  You will be able to find a "bad" angle if you try, but it is fairly specific...90 degrees to the rows is fine, somewhere around 5 degrees  probably not..   A tire tractor couldn't even think about running 7 mph at 90 degrees to old corn rows.