Originally Posted by schang
Ok, one burning question, re rear derailers: "Within a given brand/style of rear derailer, all 'speed numbers' are generally interchangeable. This applies to all indexable models, basically everything manufactured since the around 1990." -- So what *is* an indexable rear derailer? It seems to me that if a rear derailer is able to shift through all the gears using a friction shifter, it should also be able to do so with an index shifter.... The barrel adjuster on newer rear derailers I'm sure helps make it much more reasonable to keep things in adjustment, but other than that, is there really a difference?
Theoretically all derailers are "indexable" but before indexed shifters became the norm for derailer gearing in the late '80s, the travel ratio (cage/cable) was not rigorously kept constant accross different models, since it didn't matter before the advent of indexing.
In addition, derailer and sprocket design has gradually improved over the years, so the newer models require less skill to shift, making them more compatible with indexed shifters. With many older derailers, you needed to slightly "overshift" the lever to initiate the shift, then move it back a skosh to get the chain to run straight once the shift had been completed.
I have successfully indexed various older derailers, but some of this sort of technique is still needed occasionally.
My first ever indexed derailer system used original Dura-Ace S.I.S. 6-speed levers, a Sun Tour Cyclone derailer, modified Regina Oro 12-22 6-speed freewheel and Sedisport chain. I drilled and tapped the Cyclone derailer to permit me to install a cable adjusting barrel.
I rode this system for many years, even though the 52/42/28 Biopace chainrings greatly exceeded the capacity of the Cyclone derailer. (I could only use the two or three largest rear sprockets with the 28 chainring, but those were the ones I wanted with it anyway)
Sheldon "Sturmey-Archer Had Indexed Shifters 100 Years Ago" Brown
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