Every standard derailleur system has a derailleur hanger. Everyone? Not for Sram. The market leader from the USA wants to change our understanding of derailleurs. With its latest shifting system called “Eagle Transmission”, the rear derailleur sits on the axle of the rear wheel and creates a direct connection to the cassette.
Radical. First-of-its-kind. Game-changing. In Sram’s press information, such attributes alternate briskly. Understandably, the manufacturer is completely convinced of its product. It would be strange if it wasn’t. And indeed, there are a lot of new approaches in the system. Here, in brief, you can find out the basic information and how relevant it could become for ebikes.
1. What is so new about Eagle Transmission?
2. What are the advantages of Eagle Transmission?
3. Can I use Eagle Transmission on my ebike?
4. What requirements does it have to meet?
5. Which components are approved for use on an ebike?
6. Which other components belong to the group?
7. Can Eagle Transmission be combined with other Eagle groupsets?
1. What is so new about Eagle Transmission?
With Eagle Transmission, Sram presents a completely new groupset. An innovation can be discovered in every component. Nevertheless, everything more or less revolves around the new way of shifting – namely without the aid of a derailleur hanger. Consequently, there is the most to say about the rear derailleur.
The decisive question is of course: if the rear derailleur is no longer held by a derailleur hanger, who or what will take over this task from now on? A separate interface does this. Mounted on the wheel axle, it holds the rear derailleur in place. The interface docks on both the inside and the outside of the dropout. In Sram jargon, this is called “full-mount attachment”. And while we’re on the subject of terms, here’s the next one: T-Type. This addition identifies all parts of the drivetrain that are suitable for Eagle Transmission. A rear derailleur for Eagle Transmission is therefore a T-Type rear derailleur, a cassette a T-Type cassette and so on. You may come across this more often in the future.
From now on it gets magical
Just like the rest of the groupset, the rear derailleur is designed to be electronic and wireless. The Eagle AXS groupset sends its regards. Coupling and setup of the rear derailleurs work identically to their counterparts that have been available for a few years. Sram calls the lower shifting wheel the Magic Wheel. It is supposed to keep turning even if an object gets stuck in it.
The somewhat unconventionally curved “inline cage” owes its shape to the fact that it aligns the chain with the front chainring in each gear. Supposedly, this supports particularly smooth and quiet shifting.
The derailleur hanger also misses the usual adjustment screws on the rear derailleur. Since the rear derailleur hangs in the same position on every bike, such adjustments become superfluous. Installation, setup and above all maintenance of the rear derailleur should therefore be noticeably reduced.
Better not to fall
As a disadvantage of this luxury, Sram reckons that the battery life of a Transmission rear derailleur is shorter than that of an Eagle AXS rear derailleur. The reason for this is a higher cage damper force, which requires more energy, especially when shifting in the inner gears.
Speaking of force. In the past, the derailleur hanger compensated for the force acting on the rear derailleur during a fall by bending or even breaking. After that, the derailleur hanger was ruined, but the rear derailleur and frame were undamaged. This protective mechanism is missing from Eagle Transmission. Sram relies on its novelty being extremely robust in the face of lateral and frontal impacts. How justified this confidence is cannot be assessed at present. What should be clear is that a new T-Type rear derailleur will exceed the price of a new derailleur hanger many times over.
At the beginning, the Eagle Transmission cosmos consists of the following three groupsets:
- XX SL Eagle Transmission
- XX Eagle Transmission
- X0 Eagle Transmission
Looking at the past and relevant market mechanisms, it is considered certain that this list is likely to grow in the coming years.
Full Eagle Transmission Eco-System
As already indicated, Eagle Transmission is much more than “just” a new shifting standard that is padded out with existing components to form a new groupset. The group includes new cassettes with sprockets covering a spectrum from ten teeth to 52 teeth, lighter and ergonomically improved controllers, new bashguard options for chainrings, and cranksets with power meters integrated either in the spider or on the shaft. Unfortunately, these cranksets in particular are not approved for ebikes.
2. What are the advantages of Eagle Transmission?
Omitting the derailleur hanger inevitably changes the position of the rear derailleur in the bicycle. The rear derailleur moves further inwards and a little closer to the cassette. In our opinion, this is primarily a benefit for all bicycles with which you are actively riding off-road. Stones, roots and other obstacles can no longer scratch the rear derailleur so easily. Accordingly, the chances of a defect during the ride or even the unwanted end of a tour decrease. We will probably encounter the new system primarily on mountain bikes.
At the same time, it is easier to mount and adjust the rear derailleur. However, we consider a more efficient power transmission or similar unlikely. The shifting performance should be at least equal to that of an Eagle AXS groupset in terms of precision and speed.
3. Can I use Eagle Transmission on my ebike?
Basically yes. Sram guarantees full compatibility for the XX Eagle Transmission and X0 Eagle Transmission groupsets for e-mountain bikes. This statement most likely includes all pedelecs. Whether the use on speed pedelecs is also included is not clear from the manufacturer’s announcement.
However, the manufacturer openly advises against mounting the cassettes and chains of the weight-optimised XX SL Eagle Transmission shifting group on ebikes. These components are specially designed “for the lightest weight applications” and could wear out prematurely on ebikes.
4. What requirements does it have to meet?
Here comes the most serious restriction to the previous statement. At the moment, Eagle Transmission is an almost closed system. Basically, you can only ride the standard on an ebike that is equipped with it as standard.
Fortunately, there is at least one exception: If your ebike is equipped with a UDH derailleur hanger, you can switch from the current components to Eagle Transmission. UDH stands for Universal Derailleur Hanger. The abbreviation refers to an attempt by Sram to establish a specific, standardised thru-axle derailleur hanger on the market across all bicycle manufacturers. So far, however, it has remained an attempt. UDH has not penetrated the market to the extent Sram had hoped. As an example, here are six brands and their number of UDH ebikes:
- Cube: 0
- Giant: 0
- KTM: 0
- Scott: 0
- Trek: 2
- YT: 2
Sram lists UDH-compatible models from all manufacturers at bikefinder.sram.com. If your model is listed there, you can upgrade your ebike to Eagle Transmission.
5. Which components are approved for use on an ebike?
Chainrings
With a focus on durability, Sram has optimised several chainrings to withstand the high torques and associated wear on an ebike over thousands of kilometres.
E-MTB chainring 104 LKD
- For use on cranks with a bolt circle diameter of 104 mm
- Material: steel
- Sizes: 34 teeth, 36 teeth, 38 teeth
- Compatibility: X-SYNC II, AeroGuard
E-MTB chainring for Bosch
- Specially for use on ebikes with Bosch drive
- Material: steel
- Sizes: 36 teeth, 38 teeth
- Compatibility: X-SYNC II, AeroGuard
Direct-Mount E-MTB chainring for Bosch
- Specially for use on ebikes with Bosch drive
- Material: steel and aluminium
- Sizes: 36 teeth, 38 teeth
- Compatibility: AeroGuard, complies with standard EN 15194:2017
Direct-Mount E-MTB chainring for Brose
- Specially for use on ebikes with Brose drive
- Material: steel and aluminium
- Sizes: 36 teeth, 38 teeth
- Compatibility: AeroGuard, complies with standard EN 15194:2017
Direct-Mount E-MTB chainring for Shimano Steps
- Specially for use on ebikes with Shimano Steps drive
- Material: steel and aluminium
- Sizes: 36 teeth, 38 teeth
- Compatibility: AeroGuard, complies with standard EN 15194:2017
Cranksets
To combine the lowest possible weight with maximum stiffness, Sram uses a mix of carbon fibres and a foam core for the new cranksets. In addition, various bashguards can be optionally added to the crank. The models for ebikes are compatible with the “Gap Cap” cover so that cranks from Bosch and Brose can be easily integrated.
XX Eagle E-MTB crankset
- Material: Carbon and foam
- Compatibility: ISIS
- Lengths: 165 mm, 170 mm, 175 mm
X0 Eagle E-MTB crankset
- Material: aluminium
- Compatibility: ISIS
- Lengths: 160 mm, 170 mm, 180 mm
Chain
Design enthusiasts might have found their favourite piece in the Eagle Transmission chain. Its top side is completely flat and thus reminiscent of chains from the BMX sector. Functionally, we consider neither advantages nor disadvantages in the design with the flattop profile. Due to the massive hollow pins, two chains of the group are approved for use on ebikes.
XX Eagle Transmission Flattop chain
- Top: Flattop profile
- Bottom: Smooth Shift profile
- Hard chrome finish
- solid hollow pins
X0 Eagle transmission flattop chain
- Top: Flattop profile
- Bottom: Smooth Shift profile
- hard chrome finish
- solid hollow pins
Cassettes
With Eagle Transmission, the cassette and rear derailleur function as integrated and interdependent transmission components. Like the chainrings, the teeth on the sprockets of the cassettes feature the advanced X-SYNC-II design. Compared to the previous 10-52 cassettes of the Eagle drive, the manufacturer has slightly changed the gradation within the cassette. Instead of a 36-tooth sprocket, a 38-tooth sprocket is used. The next largest sprocket now has 44 teeth instead of 42. Sram promises greater stability and more precision for the cassette, as there would be fewer extreme chain angles across the entire transmission range.
XX Eagle Transmission cassette
- Material: steel, aluminium
- Gears: 12
- Sprocket: 10-52
- Chainline: 55 mm
- Technology: X-SYNC II, X-DOME
X0 Eagle Transmission cassette
- Material: steel
- Gears: 12
- Sprocket: 10-52
- Chainline: 55 mm
- Technology: X-SYNC II, X-DOME
6. Which other components belong to the group?
Rear derailleurs
- XX SL Eagle Transmission rear derailleur
- XX Eagle Transmission rear derailleur
- X0 Eagle Transmission rear derailleur
AXS Pod Controller
Cranksets
- XX SL Eagle Transmission crankset
- XX Eagle Transmission crankset
- X0 Eagle Transmission crankset
- XX SL Eagle AXS Transmission Power Meter crankset
- XX Eagle AXS Transmission Power Meter crankset
- X0 Eagle AXS Transmission Power Meter crankset
- XX Eagle AXS Transmission left arm spindle power meter
- X0 Eagle AXS Transmission left arm spindle power meter
XX SL Eagle Transmission cassette
XX SL Eagle Transmission Flattop chain
Chainrings
- Eagle Transmission Direct Mount chainring
- Eagle Transmission Thread Mount chainring
7. Can Eagle Transmission be combined with other Eagle groupsets?
Yes and no. Some of the Eagle Transmission components are backwards compatible. This means that in some cases you can combine them with older parts. For example, AXS Road single chainrings are compatible with the new T-Type chains. In the same way, T-Type chainrings can be used with the chains of current Eagle drivetrains. Sram also signals the green light for the use of the new POD controllers on older Eagle AXS drives. Eagle Transmission is also compatible with the eTap AXS Wireless Blips.
However, some things cannot be achieved. For example, an Eagle Transmission bashguard can only be mounted on a corresponding Eagle Transmission chainring. A mix of previous Eagle chainrings with Eagle Transmission chains is also not approved. In general, the Eagle Transmission chain is not suitable for any 12-speed drive from Sram, although it looks very similar to a 12-speed road bike chain. And as mentioned before, the Eagle Transmission rear derailleur and cassette require a UDH-compatible frame.
Pictures: SRAM Deutschland GmbH
