CGOAB is a web site that has made it relatively easy to post journals for touring cyclists. Below is a link to the 2 journals on there that are specific to the ring road.
In addition there are about 8 more journals about Iceland tours. There is a guest book attached to the journals where you can either offer thanks, or praise, or ask a question from the author. It seems most people are happy to respond to questions.
I looked into this ride very seriously and did a lot of research on it but in the end I will be putting it off to 2018. The pictures I've seen of Iceland are just fantastic and I'm really looking forward to my trip. What I have read from multiple sources was that the ring road is pretty narrow and twisty and the Icelanders are pretty zippy drivers and it's frequently foggy. So my take away was to get pretty serious about visibility. Also you would hear again and again that some of the pitches on the road were really steep (like 20%) so you want to make sure your bike has the gearing for it.
Have a great trip.