Shimano Ultegra Di2 R8150 12-speed electric road bike rear derailleur

Shimano ’s Ultegra R8150 rear derailleur is the centrepiece of the groupset. Indeed, it is through this component that much of the information passes. It features Shadow+ technology to integrate seamlessly into the rear of the bike and provide precise and rapid shifting. When paired with the hydraulic shifters, you have a wireless drivetrain. If you stick with cable-actuated technology and the ST-8150 shifters, you’ll need to use the wired system. Charging is also carried out via the derailleur using a specific cable – the same one required to charge the Shimano power metre (9100/9200/8100P). Capacity is important as you can now use a 34-tooth cassette. It is, of course, possible to choose an Ultegra or Dura-Ace cassette, but always a 12-speed version. The battery must be a BT-DN300 version, and the SD-300 version.

The E-Tube app Shimano can still be used with this new groupset; it allows you to optimise the ergonomics and customisation of your components.

Technical specifications

- Medium-profile sprockets: 11-28 to 11-34 cassettes in 12-speed configurations
- Manufacturer’s weight: 262 grams (manufacturer)
- Part number Shimano IRDR8150A
- Compatible with Dura-Ace R9200 12-speed components
- E-Tube compatible
- Brand Shimano

262g

Presentation and review of the new Shimano 12-speed groupset on velotech.fr: New Shimano 12-speed road groupset: R9200 and R8100

Questions and Answers

What is the Shimano Ultegra Di2 R8150 rear derailleur?

The Shimano Ultegra Di2 RD‑R8150 rear derailleur is an electronic rear derailleur designed for road bikes fitted with a Shimano Di2 12-speed drivetrain. It ensures fast, precise and silent gear changes thanks to Shimano ’s electronic shifting technology.

Which Shimano groupset does this derailleur belong to?

The RD-R8150 is part of the Shimano Ultegra R8100 series, a top-of-the-range groupset designed for competition and intensive road cycling. It sits just below the Shimano Dura-Ace R9200 in the Shimano range.

How many speeds does this derailleur support?

The Shimano Ultegra Di2 RD‑R8150 rear derailleur is designed for 12-speed drivetrains. It works with Shimano 12-speed road cassettes such as the CS-R8100 or CS-R9200.

What is the maximum cassette size it supports?

The derailleur can be used with a cassette of up to 34 teeth. This allows you to use gear ratios suitable for mountain riding or long rides.

What is the derailleur’s total capacity?

The derailleur’s total capacity is 39 teeth, with a maximum difference of 16 teeth between the front chainrings.

Is the derailleur completely wireless?

The system is semi-wireless:

communication with the shifters is wireless

power is supplied by an internal battery connected to the derailleur via a cable.

This design improves reliability whilst simplifying installation.

Can the derailleur be connected to a smartphone?

Yes. The derailleur can connect via Bluetooth and ANT+ to communicate with the E‑Tube Project app Shimano. This allows you to:

customise the gears

updating the firmware

to check the battery status.

Does the derailleur have a battery indicator?

Yes. It has a built-in LED that indicates:

the battery level

pairing mode

the derailleur adjustment mode.

How much does the Ultegra RD-R8150 Shimano weigh?

The derailleur weighs approximately 262 g, making it a lightweight, high-performance component for modern road bikes.

What Shimano technology is used on this derailleur?

The derailleur uses Shimano Shadow RD technology, which offers:

a compact profile

better protection against impacts

quieter operation.

In summary: the Shimano Ultegra Di2 RD-R8150 is a top-of-the-range electronic rear derailleur, designed to deliver ultra-fast gear changes, high precision and advanced connectivity for modern road bikes.