This seems to be a regular post audax thing for me.
For a day or two after a ride, my achilles tendons click when I walk downstairs. There's no pain or swelling, but it is annoying.
It seems related to the total workload in the ride - an easy flat ride on gears probably won't make it happen, but a tough hilly ride on fixed (like yesterdays) will (and has).
Could this be a precursor to something more sinister, or is it just the way I'm built?
I was thinking of trying some stretches, but have read that achilles stretches can do more harm than good.