A constant chain length between freewheel and upper pulley is important to rear derailleur shifting performance - it gurantees consistency. But so is shortness of chain here which makes for a quick change without overshifting and this is why the Simplex derailleurs work so much better than Campys. And that is what Shimano has achieved with all its indexed derailleurs and which is how SunTour sadly failed that relied upon the shift lever to give overshifting which was not necessary with Shimano's rear mechs. Shimano combined the top sprung pivot of the Simplex with SunTour's slant parallelogram.
Hilary Stone, Bristol, England
Mark Petry wrote:
> But the best shifting bike I own is my Mercian which is equipped with
> mid-80s Shimano Deore (r) and Campy Record (F) changers, cheap shimano f/w,
> Sachs chain, and Suntour barcons. This setup for some reason shifts as
> smoothly as indexed, very positive and crisp, with a wide "sweet spot" in
> every gear.
>
> In "The dancing chain" Berto does a litte discussion at the end about what
> makes a derailleur shift really well. It has to do with maintaining an
> optimum length between the freewheel cog and top pulley on the derailleur
> cage across the entire shifting range, on both the big and small rings.
> According to HIS analysis, the Campy by design could not shift as well as
> the slant parallelogram Suntour/Shimano products.