A Peculiarity of Shimano Di2 That You Have To Be Aware Of

from Rookie’s Keyboard

Hello, friends

It’s Monday a.k.a. time for a new lesson here at RookieJournal.com – the site that helps rookie cyclists get their bike theory to the next level. 

Today, I’ll tell you a few peculiarities about Shimano Di2 that you have to be aware of if you’re planning on purchasing the setup.

Before getting a Shimano Di2 group set you have to know that in the ideal situation, it is coupled with a Di2-compatible frame with internal cable routing. This method will result in the cleanest and most aesthetic look. 

However, it’s also possible to use an external Di2 kit to mount the group set on non-Di2 frames.

Dedicated Frames

Di2-ready frames are the only way to have a seamless integration of the setup. 

The cables go through the handlebars, and the frame’s tubes and meet at the bottom bracket shell. The battery is located in the downtube or the seat tube.

Only small parts of the cables inserted into the derailleurs could be seen. If slick looks are the goal, a Di2 frame is hard to beat.

The Downsides 

Of course, as with everything in life, there are some downsides to relying solely on Di2 frames.

The amount of frames built for the Di2 system is limited and consequently so will be your choices.

And if you already have a nice and comfortable frame, flipping it for a new one could be somewhat annoying.

Also, keep in mind that Di2 frames could be hard to resell simply because few people are looking for one.

Compatibility Check

The fastest way to learn whether you have a Di2-ready frame is to check the frame’s specifications online.

If there’s no info, examine the frame. If it’s compatible, it will have exit points (holes) in it for the cables.

You will find one hole next to the front derailleur and one in the rear derailleur chainstay.

Also, the bottom bracket shell will have openings leading to the frame’s tubes.

But to know if the frame has this option, you will have to remove the bottom bracket and examine the shell.

Note: Some frames store the battery in the downtube via a screw inserted from under the frame. If the frame has this option, the mounting point will be easy to spot on the downtube.

Di2 Kits

Di2 kits are awesome as they can work on most frames because the cables are routed on the exterior.

That said, the junction box (Shimano SM-JC41) could create a non-compatibility issue.

Normally, it is installed under the bottom bracket via a single bolt. But if the bottom bracket doesn’t have threading, an alternative solution will be needed.

The underside of road bottom bracket shells often has a plastic piece with two channels guiding the gear cables. That unit is secured to the frame via a bolt threaded into the bottom bracket too. 

Since the Di2 system eliminates the regular shift cables, the junction box can be mounted via the thread for the shift cable guide.

Storing The Battery

In the ideal scenario, the Di2 battery is placed inside the seat tube or the downtube. If the seat tube is too narrow, however, the battery won’t fit. 

The water bottle mounts on the seat tube will narrow the internal diameter of the seat tube even more and amplify the misfit.

In similar cases, the battery can be stored externally with the help of an adapter sitting on the downtube or a chainstay.

The Rest of the Components

Even if you find a way to mount the needed tech outside of the frame, the system won’t work if the rest of the parts can’t be integrated.

If the frame is vintage, its rear hub spacing is about 120mm and won’t work. Modern road cassettes (including Di2) demand 130mm spacing with rim brakes and 135mm with disc brakes. 

Another cassette cannot be used because the system works best when all of its components are original. 

But let’s be real, it’s unlikely that someone will try to install such an advanced shifting system on a road bike from the 80s.

Ok, friends. It’s time for me to go to work now. The warehouse is waiting for me. 

I just wanted to share the info above as just yesterday I was analyzing the Di2 system myself.

Until next time, 







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