My last two rides were approx. 300 miles. Not much but meaningfull. I came out with a back pain both times, much worse today. I haven't changed anything on my bike since I did back to back 325+ miles in May. However, I have changed a few things to my clothing. In the Spring, I was wearing my Aerostich. This week, I was wearing a mesh jacket with full body armor, including a back protector. I will try without it. Anyone out there has experienced back pain and found a way to cure it. Thanks for your help.