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>Multi-range gearing involves chainring differences that are much larger than the jumps on the rear cluster. The idea is that you use the front derailer to select a general gear range, and use the close-ratio jumps in back to select various gears within the range. Typically these systems call for double shifting when going between ranges, if you're concerned about a smooth gear progression, but most shifting is done with the rear alone.
>The multi-range system is commonly associated with 8-/9- or 10-speed clusters, but can be used with fewer rear sprockets and a wide-range double chainring setup.
>I've long favored this approach myself. For instance, when my OTB was a 2 x 5 "10 speed" it had a 51-28 crankset, with a 14-24 freewheel. I used a slightly shorter than normal bottom bracket axle, to make the 51 tooth chainring line up with the middle of the rear cluster. This let me use all 5 gears with the 51 tooth ring. As a result, the 28 tooth ring could only work with the two or three biggest sprockets, but that was OK. Most of my riding was done on the 51 tooth ring, keeping my shift pattern simple and smooth. When I would come to a serious climb, I had the small chainring to get me up it. This was basically a variation on the "alpine" concept.
>Below is a photo of a later version, with a 6-speed freewheel.
>OTB Drivetrain
>Even today, my Hetchins is equipped with a 50-28 double crankset and a 12-28 9-speed cluster. I find this setup extremely convenient, but you will never find a stock bike set up this way, because it isn't "idiot proof"--If a clueless rider were to try riding in one of the small-small crisscross gears, it would not work at all well, so no manufacturer could offer this as a stock setup for fear of warranty claims.
It's a Sheldon idea.
There's be a 20 tooth gap. He had a 23t gap.
