Not doing RAGBRAI this year, but have done it a number of times before. I've done it on a Raleigh Gran Sport, a Raleigh International (as a fixed gear), and some other steel bikes.
The better question is: what does the Father of RAGBRAI ride??
Well, I snapped this photo in 1991 of John Karras, and I can't tell what the bike is.
high resolution version:
https://live.staticflickr.com/65535/...81cb8_4k_d.jpg
Steve in Peoria