Review: Shimano Dura-Ace Di2 9150
Aug 31, 2020
article & images by Nick Salazar
Looking back at our first Di2 review almost 9 years ago, we see that Shimano has advanced significantly. Basically everything we hoped for has indeed been achieved, most notably the Synchro Shifting platform, which is awesome.
Our headline for this review of "the 1x killer" is barely hyperbole. This thing really lets you just focus on the task of pedaling your bike. No looking down, no looking back. Just "harder" or "easier" on your shifters, and the system takes care of the rest.
Setup is relatively easy, save the one wrinkle of getting all your wiring in place. But that's generally not too bad. Plus, once set up, it works like a dream, and you get all the gears you could ever want. Moreover, Shimano has long offered trickle-down in the form of Ultegra Di2, which offers all the same advantages, including Synchro.
Drawbacks are hard to come by. But, battery placement can still be a minor headache, easier for a seasoned pro mechanic than for the consumer. And unlike with SRAM's eTap, it is usually more difficult to just carry a spare battery. External battery systems are rare these days; most systems use the internal battery, which is usually several bolts (and tools) away from replacement. So even if you did carry a spare (which is unlikely and inconvenient by comparison to SRAM), the swap is simply going to be impracticable on the road. On the other hand, Shimano's battery is significantly higher in capacity than the smaller SRAM batteries. Plus, the low battery indicator is functional, by causing the front derailleur to stop shifting several *hundred* miles before the battery dies completely. So, in any ordinary situation, you have LOTS and LOTS of time to figure out your charging situation. At minimum, even for the longest of rides, you will have at least 24 hours before critical failure with Shimano's system.
Compared to mechanical systems, of course, the battery itself is a drawback. If you are an occasional rider, you can't simply ride at a moment's notice unless you take care to monitor your system's battery life and keep it topped up. If you leave your bike for a few months over the Winter, and suddenly find a nice Spring day for a ride, you may come to a dead bike that requires charging. Even the dedicated and stalwart athlete can run into this issue when injury rears its ugly head. I personally have had this problem. And in the wake of injury, discovering an unexpectedly-dead bike when you are FINALLY ready to train is just one last insult to your literal injury, and can be extremely annoying.
To be fair, these battery-related drawbacks have nothing to do with Shimano. They are simply a problem inherent to an electronic drivetrain. There are just a couple ways around this. One is to ALWAYS charge your bike. Any time it is parked, plug it in. You do it with your phone. You do it with your laptop computer. Just do it with your bike too. A second solution is to use an external battery, and ALWAYS carry a spare. This will still involve periodic charging, as even an unused battery will slowly discharge over time. I guess a third potential solution would be to set an alarm to charge, roughly 3 hours before you ride, to ensure you have enough charge for any distance. None of these solutions are perfect. And any battery-powered drivetrain, by definition, adds an element of inconvenience compared to a mechanical one.
The question is whether, on the whole, that inconvenience outweighs the benefits of the electronics. And on the whole, I say it's an absolute and definitive yes. However, I would not say that means all bikes should be electronic. Whenever I build a bike that is only sporadically used, I still consider and frequently go for a mechanical drivetrain.
SRAM went deep into the 1x space (which we have loved for the better part of a decade), and on the other hand, Shimano decided to eschew 1x in favor of the synchro shifting first pioneered by Fairwheel Bikes with their so-called 'Sequential Shifting' mountain rig, using the very first Di2 group and some custom electronics and programming. By 2019, Shimano caught up to that idea, incorporated it into its system, and created a beautiful and seamless way to make synchronized derailleur movement work for any rider with the bare minimum of technical panache. So at this point, SRAM and Shimano have reached the apex of these respective design philosophies. SRAM is king of wireless and 1x. Shimano is king of wired and 2x. Trying to pick a winner is just too difficult. I absolutely love riding both of these groups, and can't find a clear winner. But suffice it to say, Di2 9150 is an absolutely outstanding group, and gets my highest endorsement.
Shimano's Magnum Opus has arrived.