Condensed Answer: Ideally, the Shimano Di2 group set is combined with a Di2 compatible frame with internal cable routing. This combination gives the cleanest and most aesthetic finish. That said, one can also use an external Di2 kit to install the group set on a great variety of non-Di2 frames.
The Advantages of Using a Di2 Ready Frame
- Clean Look
Di2-ready frames make the integration of the electronic group set seamless. The cables run through the handlebars, the tubes and meet at the bottom bracket area. The battery sits in the downtube or the seat tube and is secured via a bracket.
Only parts of the cables going into the derailleurs remain visible. If looks are a priority, a dedicated Di2 frame is hard to beat.
- Easier Installation
A Di2 frame makes the installation of the kit easier as there are fewer decisions to be made in regard to cable routing.
The Downsides Of Using a Di2 Frame
- Limited Choice
The number of frames compatible with the Di2 system is small and limits the rider’s choice.
- A Potentially Unnecessary Switch
The user may have to give up an otherwise comfortable and “healthy” frame for a new one.
- Restricted Resale Potential
A Di2 frame could be hard to resell due to the limited number of people that will be interested in it.
FAQ: How can I know that my frame is Di2 compatible?
The quickest way to learn is to check the frame’s specifications online.
If that information is not available, it’s necessary to examine the frame. If the frame is designed for a Di2 system, it will have exit points (holes) in it for the cables.
There will be a hole next to the front derailleur as well as one in the rear derailleur chainstay.
Furthermore, the bottom bracket shell will have entrances leading to the frame’s tubes. To know whether the frame has this feature it will be necessary to remove the bottom bracket and examine the shell.
It’s also worth mentioning that some frames store the battery in the downtube via a bracket that’s screwed under the frame. If the frame has this feature, the mounting point will be visible when examining the downtube.
FAQ: Is the external Di2 kit compatible with all frames?
Since the cables are routed on the exterior of the frame, the answer is yes most of the time.
The junction box (Shimano SM-JC41) could create a non-compatibility issue, however.
The junction box is installed under the bottom bracket via a single bolt. If the bottom bracket doesn’t have threading, one would have to use an alternative way to mount it. With a little creativity, a solution can be found, but it won’t be as neat as the original mounting system.
That said, the underside of road bottom bracket shells often has a plastic piece with two channels guiding the shift cables. That piece attaches to the frame via a bolt threaded into the bottom bracket too. Since the Di2 system eliminates shift cables, the junction box takes the guide’s place.
Storing The Battery
Ideally, the Di2 battery is stored inside the seat tube or the downtube. If the frame’s seat tube is too narrow, however, the battery will fail to pass. Also, the water bottle mounts on the seat tube can narrow the internal diameter of the seat tube even more and create a problem.
That said, the battery can also be stored externally via an adapter sitting on the downtube or a chainstay.
Compatibility With The Rest of the Components
It may be possible to install the needed tech externally, but that won’t mean much if the rest of the group set isn’t compatible with the bike.
For example, if the frame is old-school, chances are that the rear hub spacing is about 120mm. Meanwhile, modern road cassettes require 130mm spacing when using rim brakes and 135mm when relying on disc brakes. If that condition isn’t met, the frame won’t be able to accept a hub that’s compatible with the Di2 cassette.
Another cassette should not be used because the system works best when all of its components are original. Otherwise, one will not experience the benefits that an electronic shifting system can offer.
That said, it’s unlikely that someone will try to install such an advanced shifting system on a retro road bike.
Most road bikes out there will readily accept the parts, although some adjustments could be needed.
Summary: What You Need To Know
- Ideally, Shimano Di2 is installed on a Di2-compatible frame. This combination offers an easier installation and a clean setup. Only small parts of the cables connecting to the derailleurs remain visible.
- Shimano Di2 can also come in the form of an external kit designed specifically for frames that aren’t Di2-ready by default. The main requirement is to have a threaded slot under the bottom bracket in order to install the junction box. All else, including the battery, can be mounted externally.