Domo Arigato, Mr. Shimano

In the workshop, “the sound of shifting is changing from subtle clicks to the whir of a dancing robot”.

Di2 Front Derailleur

With multiple 2011 Tour de France stage wins for Campagnolo’s electronic shifting system, and the entire podium riding with Shimano’s DI2, it’s no wonder that electronic shifting is a hot topic. So, what’s it all about? Electronic shifting is functionally identical to mechanical shifting, the rider tells the shifter what to do, the shifter moves the derailleur, and the derailleur moves the chain from one gear to another. The only difference is the method of communication between the shifter and the derailleur.

Di2 Shift Lever

With a mechanical system, the shifter utilizes the hand strength of the rider to move a lever attached to a cable. A system of ratchets and pawls (not, as has been rumored, mystical miniature Italian or Japanese laborers, but that’s for a different article) in the shifter mechanism create finite movements that pull the cable just the right distance. These “indexes” allow the derailleur to align perfectly with the gear of choice. With the electronic system, the force of movement is powered by small motors in each derailleur, and a microprocessor tells the motors exactly how far to move. The shifter mechanism becomes simply a switch, with two buttons telling the motors which direction to move. Some advantages of this being that the shifting no longer relies on hand strength, and eliminates the numerous intricate small moving parts of the shifter mechanism. This also makes electronic shifting far less influenced by it’s environment. Current electronic systems are well sealed from the elements, Campagnolo claims it’s electronic system will function even while completely submerged. By being impervious to water, dust and road grit, these aspects no longer effect the relationship between the shifter and the derailleur.

 

To understand why electronic shifting is a significant leap forward, it is important to point out what is eliminated altogether. Cables are the Achilles heel of any shifting system. No amount of mechanical precision in either a shifter mechanism or derailleur will make a difference if the cable is not traveling smoothly through it’s housing. In the 50′s and 60′s, housed cable systems were standard equipment on bicycles. However, Raleigh along with other bicycle manufacturers of the era still produced bicycles with rod and lever actuated brakes for foreign export to places like India and South Africa. Although the housed cable system was well established at that time, the climate and inaccessibility to spare parts in these regions facilitated the need for the antiquated yet more reliable and serviceable rod systems. Housed cables have come a long way since then, but one muddy cyclocross race or rainy Spring Classic can wreak havoc on the vulnerable housing/cable interface.  Another issue is compressibility. Since pressure is applied to both ends of the housing, the compression changes the effective length of the housing. Modern housing is designed to resist compression by incorporating strands of wire running it’s length, but input of the shifter is always a finite movement to the derailleur, so any slight change in the distance between the two can effect the adjustment of the shifting. Shimano lists 100 common reasons for poor shifting in their mechanic’s handbook, of them 34 are cable/housing related.

Di2 Diagnostic Tool

While traditionalists may consider electronic shifting to be a gimmick, signs point to it becoming the standard for bicycles. Campagnolo has invested over 20 years in research and tooling for it’s electronic groups, a major gamble for a company as steeped in tradition as they are. Shimano’s offering of an Ultegra level electronic package suggest that the concept can be close to a reasonable price. As with all electronics, the drive of progression is in lowering in cost as well as product improvement. The future of bicycles it seems, belongs to electricity.

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