Shimano Ultegra Di2 Shadow RD-R8150 12-speed Rear Derailleur

Item number: 84390
Ultegra Di2 Shadow RD-R8150 12-speed Rear Derailleur - anthracite/long
Ultegra Di2 Shadow RD-R8150 12-speed Rear Derailleur - anthracite/long
Ultegra Di2 Shadow RD-R8150 12-speed Rear Derailleur - anthracite/long
Ultegra Di2 Shadow RD-R8150 12-speed Rear Derailleur - anthracite/long
  • 100 day return period
  • Online since 1998
  • Trusted Shop 4.91 / 5.00

The Ultegra RD-R8150 Rear Derailleur by Shimano - Your Di2 centre

The RD-R8150 12-speed rear derailleur is the central element of the Shimano Ultegra Di2 road bike groupset when it comes to semi-wireless as well as fully-wired shifting. It has even more to offer than a conventional rear derailleur, since it communicates wirelessly with the shift/brake levers via the built-in wireless chip in the disc brake version. In the rim brake version with a cable connection to the STIs, it is responsible for coupling the components. This is done via a function button, which is also used to adjust the rear derailleur. You can also use the button to check the battery level, change the shift mode from manual to Synchro and Semi-Synchro Shift, and establish a Bluetooth connection to a bike computer or smartphone. An LED display helps you to do this. The rear derailleur is connected to the battery via a cable, from which a cable also runs to the front derailleur and possibly to the STIs. It has a charging port that allows you to easily recharge your circuit using the matching charging cable. In racing and training use, RD-R8150 convinces with an extremely high shifting speed that clearly surpasses that of its predecessor. Its flat Shadow design reduces the risk of snagging and optimises shifting. With a total capacity of 39 teeth, you can shift 12-speed cassettes with a largest sprocket of 28 to 34 teeth. The rear derailleur consists largely of lightweight aluminium, resulting in a weight of just over 260 grams.

Information regarding the return of batteries and electrical equipment:

Information on the return and disposal of batteries and electrical equipment can be found here.


Series: Ultegra Di2 R8150
Application: Road
Gearing: 12-speed
Mount: standard (Direct Mount compatible)
Capacity: 39-tooth
Compatibility: Shimano Road 12-speed
Compatibility - Chains: HG 12-speed

Technical Information:

Derailleur Pulleys: 11-tooth
Outer Cage Material: Aluminium
Inner Cage Material: Aluminium
Other Materials: aluminium, steel, stainless steel, composite material (GFRP)


Power Cable: EW-SD300-I (1 x connection)
Shift/Brake Lever: ST-R8150, ST-R8170, ST-R7170, ST-R8060, ST-R9250, ST-R9270, ST-R9160, ST-R9180
Cassette: CS-R8100-12, CS-R9200-12, CS-R7100-12
Chain: CN-M8100, CN-M9100, CN-M7100, CN-M6100
Charging Cable: EW-EC300


- function button, charging port and wireless system in one compact unit
- Di2 wireless chip with low interference probability, high processing speed and low power consumption
- LED status display (battery, pairing, settings mode, Synchro Shift)
- takes over the function of previous wireless units in establishing a wireless connection with compatible cycling computers
- extremely high shifting speed: 58 % faster than RD-R9150
- flat design
- connected to battery via cable
- only one cage length for all gradations
- firmware updates via E-Tube Project
- 4 fluorine-coated joint bushes
- tension and guide roller bearing
- painted cage


Shadow RD
Shadow rear derailleurs from Shimano have a very flat profile, allowing for a more aggressive riding style by minimising the risk of getting stuck on obstacles. In addition, the single preload ensures that the rear derailleur does not hit the chain stay even on very uneven ground. All of this contributes to a quiet, clean-operating gearshift.

Digital Integrated Intelligence (Di2)
Di2 systems are the electronic shifting systems from Shimano. They are based on the SEIS, the Shimano Electronic Intelligent System, which takes over the index shifting function from the mechanical components, only via power cables or radio signals and not via a Bowden cable. Shifting is done by simply pressing a button. This has the advantage that no great effort is required, your concentration on the ride is not disturbed and operation is easy even with cold hands. In addition, the electronic gear changes are very fast and highly precise. There is also no risk of a defective circuit due to dirty cables or other problems. You can adjust individual settings via the E-Tube Project, such as adjusting the shifting speed, the number of shifting operations per button press or the Synchro or Semi-Synchro shifting function. Shimano offers an app for this purpose. Gear maintenance and firmware updates are also done via E-Tube, with the bike connected to a PC running the appropriate E-Tube software for more extensive workshop work.

Shimano Synchronized Shift
Shimano's synchronised shifting function is a shifting mode that automatically matches the Di2 rear derailleur and Di2 front derailleur. It is activated either via the E-Tube platform or via the rear derailleurs with a function button. Synchro Shift means that the front derailleur automatically selects a suitable gear depending on the position of the rear derailleur, while Semi-Synchro Shift means that a suitable rear derailleur position is automatically set when you operate the front derailleur. This gives you the advantage that you only have to concentrate on one side of the shifting process and are not thrown off-rhythm by sudden unfavourable changes to the gear ratio.


Max. Largest Sprocket Teeth: 34-tooth
Min. Largest Sprocket Teeth: 28-tooth
Max. Smallest Sprocket Teeth: 11-tooth
Min. Smallest Sprocket Teeth: 11-tooth
Max. Chainring Difference: 16-tooth
Total Capacity: 39-tooth
Manufacturer Number: I-RDR8150A


- 1 x Shimano Ultegra Di2 RD-R8150 rear derailleur
- 1 x Shimano TL-EW300 cable tool


  • anthracite/long: 262 g


  • anthracite/long, in stock

Rate this product

Be the first and leave your opinion!

Customer Reviews

no reviews yet

Your opinion counts!

Be the first and leave a comment!