Joined: Jul 2006
Posts: 205
Likes: 0
From: Seattle, LA, Suzhou
Bikes: Hugh Porter criterium, Davidson Discovery (touring), GT road, Nishiki Yukon MTB (which I hate)
Welcome to 51! Even if you had not taken some time off from cycling, you'd probably still have a sore back. That's one of the unfortunate side effects of age. You could probably fiddle with your bike forever and not be entirely comfy with it.
Do you stretch before and after each ride? Maybe a Naprosyn or Ibuprofen 2 hours before you ride.