Timing of the Kick in Freestyle

“If the function of the kick is primarily that of a stabilizer or neutralizer and streamliner, then coordination of the kick with the arms is very important.  If the hips are permitted to roll with the shoulders, the feet will be in a good position to thrust sidewards a the proper time, as mentioned previously.”
- James Counsilman 'The Science of Swimming'

This is one of the reasons that I stress proper rotation and the ‘skating’ drill.  When the hips are turning enough, they are sort of out of the way of the exiting arm.  And then…

“…Another important point regarding the timing of the arms and legs is concerned with the end of the pull. As the arm finishes its pull, it is pushing backwards and upward.  This action will cause the hips to be pulled further underwater if the downbeat kick does not correspond with this upward movement of the arm.”  - James Counsilman 'The Science of Swimming'

In my case, doing more of a rotation, I’m almost sideways and would be ‘fish-tailing’ if I didn’t give an opposite thrust with my kick as I was finishing that upward and, again, almost sideways movement of my arm. 

I do a two beat kick.  I trained myself to do that, changed from a six beat kick about 15 years ago.  At my age, 74, I’m not interested in hard sprints anymore.  So, I go for lots of power in my kick instead of a speedy kick. So, whether you are doing a two beat kick or six beat kick, that downward kick, same side as exiting hand, is extremely important.