I bought a road bike about a month ago and after a few weeks of riding i have developed what I believe to be Achilles tendinitis. I was physically active before cycling (running, lifting), but have never had this problem before. I am flat footed and after doing some research i think that this may be leading to my Achilles problem. Because of this, i have decided that buying inserts for my cycling shoes might be a good idea. This leads me to both of my questions. Am i right to assume that this Achilles problem may be a result of my flat feet? And if so, what kind of inserts do you recommend? From what i've read online Superfeet and Specialized seem to both be popular picks for cycling inserts. Will these inserts fit in any brand of cycling shoe, or do I have to buy a Shimano brand insert to fit my Shimano shoe?

I know there is a lot in this post but any help would be greatly appreciated.

Thanks again,
Dave