very weird coda magic road crankset

[one-eyed_jim]

Dos the catalogue say what is the difference between them and the standard 5 bolts version?

In a normal 5-arm spider, the elasticity of the materials means that a large proportion of the load goes into the first chainring bolt anticlockwise from the crank. When one attachment is combined with the crank itself, the loading is even more concentrated in the first attachment. To optimize the use of material, it makes sense to account for that in making the main attachment point heftier than the others, but obviously that means standard chainrings can't be used. This design allows the spider to be lighter, and is still stiff because of the large-diameter hoop linking the two chainrings.

But, at about the time this design came out, Shimano started improving their front indexing by adding ramps and pins to their chainrings, so while the 3-arm design saves a bit of weight, it gives inferior shifting, and the rings were very expensive to replace - and of course were only ever available in a couple of combinations. They just weren't worth the extra cost and compatibility hassles.

The CNC CODA M501 and 701 mountain cranks with monoblock CNC rings appeared and disappeared around the same time, for similar reasons.