Unless you've been living under a rock for the last two years, you've probably heard about Shimano's electronic shift system, Di2 (Digital Integrated Intelligence). The platform debuted at the 2009 Tour of California, and has been the most talked about kit since then. The general consensus among other reviewers has been two fold. First, that Di2 is the most brilliant shift system out there, and second, that it's the most expensive. The roadies have noted how well it works even under the worst conditions. Some have even said it's worth selling off all your "extra" gear in order to afford the Di2 road group. But this is TriRig, so we're giving Di2 the top-down review from the triathlete's perspective.
What did we find? Is this group nothing more than technology for technology's sake? Or is it something more? The short answer - Di2 is AMAZING, and represents a MUCH bigger improvement for triathletes than it ever was for the roadies. It is really all that and a bag of chips. When others say it's worth selling off extra bikes, bars, and superfluous equipment just for the privilege of experiencing electronic shifting, they haven't gone mad. I'm tempted to say the same thing for the tri group.
Sadly, Di2 is only available for triathletes at the ultra-premium Dura-Ace level. That means there's nowhere to save money. The road version just got some trickle-down with the Ultegra Di2, but there's no announcement of Ultegra-level TT shifters. So for now, the price of entry remains very high for triathletes. This review is based on that Dura-Ace level group.
Set up isn't as hard as you may have heard, as long as you read the manual. If your bike features internal routing, you'll be left with a very clean-looking setup.
We'll start with the overview of what this group is. At its core, it consists of a front and rear derailleur, each of which is moved by a position-aware motor. The front derailleur is also aware of the rear derailleur's position, and automatically trims itself to avoid chain rub in any position. The derailleurs are powered by a small 7.4v battery, whose 550 mAh life is enough for at least 650 miles, according to Shimano.
The shifters are where things really get interesting. They are nothing more than simple contact switches, each one sending nothing more than a "go" signal through either the up or down wire of the derailleur it's connected to. This simplicity has a side effect that is actually one of Di2's greatest features: modularity. It's incredibly easy to put different shifters in different places, merely by splicing the wires and putting another tact switch in line. We've seen Shimano realize this concept with the Sprint Shifters, Satellite Climbing shifter, and, more importantly for triathletes, the STI aero brake levers. Having those shifters out there is a game changer. We'll get to why those are so important later on in the review.
The internal wiring looks complex at first, but it's actually not too bad. The front and rear junctions act to convert signal from the shifters to the derailleurs, and connect everything up to the battery. There are a lot of wires, but on a late-model tri bike built with the system in mind, you can tuck them inside the frame, and keep them from becoming an eyesore like they are on many roadies. The connections are water-resistant, and further protected by heatshrink wrap that makes this system effectively waterproof for any riding conditions. You're free to wash your bike as normal without any risk to the electronics.
Setting up the shifters and derailleurs is mostly very easy. There are only two parts that are slightly tricky. The first is connecting all the wires in the right order, heatshrinking them all up, and stuffing them into the bike properly. It's a bit of an exercise in RTM (Read The Manual), both for the Di2 system, and whatever bike you're installing it into. Then comes the adjustment of the derailleurs, which again, is actually pretty easy, but requires you to bone up on that manual. After the derailleurs are set up, and the cables stuffed, the hassle is over, and it's over permanently. You can micro-adjust the rear derailleur from the control box very easily, to account for minor differences in your cassettes or wheels that throw the adjustment off just slightly.
The rest of the group is all from Shimano's standard 7900 group: the cranks, cassette, chain, and brakes are all the same as their non-electronic counterparts. Depending on the bike you're running, you might not be using all this stuff. Many high-end tri bikes are now using integrated brakes, and some even have integrated cranks, like the LOOK 596. You actually will get the best performance out of the group if you stick to the stock components, but I strayed quite a bit anyway, using a different crank, cassette, chain, and brakes. For the most part, things worked out fine. In fact, I should note that the carbon chainrings from Fibre-Lyte, which ordinarily require a little extra care to operate, run amazingly well on Di2. They can be shifted normally here, without having to treat them with kid gloves. This is possibly because of how strong the Di2 derailleur is, throwing the chain on with more force than a cable-actuated derailleur works, and thus not putting as much stress on the rings. Whatever the reason, I'm really happy about it. The Fibre-Lyte rings are awesome-looking, and very light.