Dura Ace 9150 Di2 Rear Derailleur

The Shimano 9150 Di2 group has been overhauled and improved as it replaces the previous generation 9050 groupset. The Dura Ace 9150 Di2 Rear Derailleur has seen some significant design and performance improvements compared to the 9050 iteration that it replaces. One notable non-difference however is the new 9150 groupset is not 12 speed. Those hoping for a 12 speed Shimano Dura Ace offering will have to wait for the next generation to be released.

The launch of the 9150 Di2 groupset from Shimano in 2016 marked the third generation of Dura Ace Di2. First introduced with the launch of 7970 Di2 in 2009, the Dura Ace Di2 system has 8+ years of evolution. Advantages of the Di2 electronic shifting system include not having to manage wire cables that tend to deteriorate over time and require frequent maintenance and replacement. Typically, the battery lasts long enough on one charge that most people would not have to charge the battery more than a few times per year.

Low Profile, Shadow Technology

Key design improvements include repositioning the derailleur inwards with respect to the chainstay mount. This allows the derailleur to be hidden and less obtrusive. It will be less susceptible to being damaged in the event of a crash. The design cue comes from the Shadow technology that was long ago implemented across the Shimano mountain bike groupsets. The result is a more compact and sleek appearance, both in terms of aerodynamics as well as functionality.

With shadow technology, the derailleur is placed inwards and lower under the chainstay and hence lower under the engaging cassette cog. This positioning makes wheel changes easier as there is less interference from the derailleur when inserting the wheel axle to the dropout. This clandestine approach is a big improvement over the previous generation and offers many benefits while shifting, changing wheels, or during a crash.

Crisp, Confident Shifting

How does it shift in comparison to the previous generation? Shimano claims that the newer design is more rapid and offers more precise shifting. Although this claim is difficult to quantify and compare directly to previous generations like the 9000 derailleur, there is no doubt that the shifting is flawless, speedy, and indeed precise. With proper setup, the 9150 derailleur does not miss a shift or hesitate even under extreme shifting circumstances like trying to go up or down multiple gears in a pinch.

Cassette Compatibility with 9150 Rear Derailleur

Since road bikes have long ago evolved from the standard 11-25 cassette ratio, the latest road derailleurs must also accommodate bigger gear ratios. The 9150 rear derailleur is designed to work with a maximum cassette size of 30 teeth, ranging down to 11 teeth on the smaller cog.

The 9150 comes in only one size. This time there is no small or medium cage style. It is a one size fits all design. This includes working properly with a compact chainset. With a maximum front teeth difference of 16, the derailleur will have no trouble managing a 50-34 compact chain ring setup. Another popular climbing chainring setup is 52-36 which is also well suited to be in the range of this derailleur. Big mountain climbers with compact gears and an 11-30 cassette will have no issues with this derailleur.

Since Dura Ace is the pinnacle of Shimano road groupsets, it is expected to be the cream of the crop with no expense spared in the design and the selection of materials. As such, the derailleur weighs in at a light weight 197 grams. For gram counters that want Di2 shifting, this derailleur compares well to its main competitors.

How does the 9150 Perform in Real Life?

The feel of the derailleur shifting under load is both crisp and smooth. Shifting is effortless and sufficiently snappy even when encountering high pedal torque situations. Synchronized shifting also helps to minimize stress on the drivetrain while maintain accurate and powerful shifting. Combined with the light shift action of the newly designed 9170 shifters, the chain breezes up and down the cassette with enough positive click feedback to be sure and satisfying.

Most Dura Ace groupset owners are likely to be more experienced riders. Counting myself among them, I feel that my old habits of shifting manually are difficult to change and this makes relying on syncro shift somewhat challenging. A complete rework of a lifetime of shifting habits would have to be re-wired and forced to allow the use of automated shifting. Syncro shift or semi syncro shift will likely work better for riding styles or terrains where the rider doesn’t want to think about cross chain gears and would prefer to let the Shimano computer control it.

Benefits of Electronic Di2 Shifting

One of the best features of electronic shifting is the auto trim. The Di2 derailleur can precisely position itself over the correct cassette cog. This makes ever shift exactly perfect and unlike cable actuated derailleurs, will not rub the adjacent cog or skip because the cable tension isn’t just right. If you are coming from a bike or groupset with cable shifting, you will notice this as a welcome improvement. There is nothing more annoying than being unable to shift smoothly into the desired gear when under stressful conditions.

Dura Ace 9150 Di2 Rear Derailleur Quality

The aesthetics of the rear derailleur are somewhere between bland and classy. It may not be eye popping or ground breaking but it looks refined, polished and of the quality one has come to expect with Dura Ace. Considering the electronics involved, the 9150 derailleur is subtle and sleek with a black anodized polished finish. The jockey wheel cage is carbon fiber and houses a jockey wheel and guide wheel.