SlushBike Rear Shift Adapter

Here's a true rolling prototype, in fact the 2nd or 3rd version of a design I've been refining for years. This is a good time to discuss it, since it's about to be retired (from SlushBike, at least). The pictures are based on the same shot, but with two apparent zoom levels to orient you to where it is on the bike.

This piece connects my favorite shifter, the Campagnolo integrated brake-shift lever ("brifter" for short), to a Shimano rear derailleur. These parts are not supposed to connect, and even if they were, the brifter is 9-speed while the cassette is 8-speed. I designed and fabricated it myself, from 6061 aluminum alloy.



The function of this adapter is to make the derailleur perceive the cable movement that is correct for its design, but which is driven by the incompatible brifter. The derailleur works by deforming a triangle where one of the sides is a stretch of cable which is pulled in or allowed to pull out. So the adapter really just shifts one point of this triangle, the one where the cable attaches to the derailleur arm and moves the pulleys. Of the three versions I've made, this is the most adjustable, so it could adapt lots of different shifter/derailleur combinations. You can see that it has a long slot for its mounting bolt (the original cable fixing bolt), and this controls the radius of the adjustment. The whole adapter can be rotated around its mounting bolt, allowing the angle of the adjustment to be set. This combination permits quite flexible positioning of the new pivot point compared with the original one.


This adapter has served me well for years, but it will be obsoleted on this bike when I convert to the internal hub.