Originally Posted by
justinzane
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.
The manufacturer's spec isn't a binary works/doesn't-work point, it's just where they feel performance drops off enough to warrant the spec. In general practice, the closer two chainrings are in size, the easier they'll shift, and the farther apart they are, the more laborious it will be. Sheldon Brown did something like you propose, a long time ago, and it works as long as you know what you're doing.
Gear Theory for Bicyclists