New SRAM rear derailleur
Anyone who has ever had to deal with a bent or even torn derailleur hanger on their bike will inevitably have wondered how bicycle designers have been able to hold on to this seemingly immature solution for decades. The filigree small parts that hold the rear derailleur to the frame are usually made of soft aluminium alloys so that they are as light as possible and can be torn off in an emergency. One task is therefore to ensure that the frame is not damaged even in the event of a minor fall.
However, the supposed advantage often turns out to be a disadvantage: the flexible part not only reduces the switching quality itself. Once bent, it usually has to be replaced because bending it back is only an emergency solution. The material is often so damaged that it breaks at the next major load.
Then it is usually difficult to get a replacement because derailleur hangers do not follow a uniform standard, but look different from frame to frame and can even change from model year to model year. The result: there are thousands of differently designed models - finding the right one can become an impossible task if the frame manufacturer cannot help directly. Then the frame is still scrap.
Eagle Transmission - Robust, simple and modular
Component manufacturer SRAM recently presented a solution to this problem with the new Eagle Transmission mountain bike groupset. Its rear derailleur is no longer attached to the derailleur hanger with the classic bolt. Instead, it hangs on two solid aluminium brackets directly on the thru axle and encloses the dropout from both sides. This makes the suspension much stiffer and more robust: videos are circulating on social media in which testers stand on the rear derailleur of bikes lying on the ground and the mechanics remain completely undamaged. A useful side effect of the design is that the rear derailleur is always positioned exactly in relation to the cassette - there is no need for tedious adjustments such as the end stops and the distance to the sprockets. The transmission rear derailleur also dispenses with the corresponding adjustment screws. In addition, the entire mechanism is moved further inwards, which means it is better protected from external influences. The rear derailleur has a modular design consisting of three parts that can be replaced individually.
To fit the groupset, the dropout of the frame must be designed in accordance with the UDH standard (Universal Derailleur Hanger) introduced by SRAM in 2019. This standard was originally intended to lead to standardised derailleur hangers on mountain bikes, with around 200 manufacturers joining in. It now appears that the Americans have paved the way for their transmission concept.
Theoretically, the Transmission groupset could also be installed on gravel bikes, as the electronic rear derailleur works with the AXS protocol and is compatible with the shifters of the Red, Force and Rival road bike groupsets. So far, however, there are very few gravel bikes with the UDH standard; examples come from Lauf or YT. Whether the solution will become established on gravel bikes or even road bikes remains to be seen - but development has already begun. Shimano and Tektro have already applied for patents for similar derailleurs.
Jens Klötzer
Editor
