Instead of gravedigging http://www.bikeforums.net/bicycle-me...ing-sizes.html, I'll start anew.

I want to know what is the largest range possible with a 110mm or 130mm double. Can one have a 48/28 -- like a 48/38/28 without the middle ring? How about a 52/26? What are the functional limitations and tradeoffs? Are there specific makers that cater to oddball setups like this?

On the flip side, what is the smallest difference between double rings that is at all useful? Is there any situation where a 53/48 or a 52/48 is useful?

I know that someone will say "just get a triple" somewhere along the line. I'm not necessarily going to run out an install a max-range double whatever the answers say. I'm trying to get a feel for what is reasonably possible, not the conventional wisdom, not the current trend.