Fitting Shimano SC-MT800 Di2 display on a Road Bike

I’m thinking of fitting an SC-MT800 Di2 Display to a road bike, like this:

…and as mentioned here by @terry_bettershifting :

It’d be to replace an SM-EW90-A junction box and EW-WU111 wireless unit, as combined 3-port junction box and wireless unit, plus the added display for gear selection/battery status.

  1. Has anyone here done this? Any gotchas to be aware of?

  2. Mounted on 31.8mm bars, does anyone know how big the gap is between the main body of the unit and the bars? The narrow gap you can see in this photo:
    Specifically, is this gap sufficient to squeeze in the rubber strap, maybe 3-4mm thick, for a bar-mounted front light? Looks a bit tight to me…

Thinking aloud: if the gap’s too tight, then I believe the SC-MT800 comes with a 35mm clamp band, so maybe I could use that with a silicone rubber band/shim to open up that gap between the display unit and bar, and fit in my light’s rubber strap.

TIA. :slightly_smiling_face:

One thing to be aware of - you need a modern battery or mount: BT-DN110 or BM-DN100. The older SM-BTR2 battery won’t work.

My SC-MT800 is currently not connected, but I can dig it up and take some photos tonight (in about three hours)

Also, the most logical place is to the right of the stem (because the band is on the left of the unit). This makes sense, but is something to be aware of.

Update: Actually, found some older photos. Uploaded here:

I’ll have a look at the clearance tonight :wink:


Terry, thanks for the reply - it’s like having a Di2 wingman :+1:

I’ve got a BT-DN110 battery and the display would be fitted to the right of the stem, trying to slot it in into the space shown here between stem and light mount, without me needing to move that light mount further off to the right:

When stretched a bit that rubber strap on the light mount is <4mm, maybe <3mm thick, so I just need a bit of a gap between the display’ unit’s body and the bars in this region (I guess the rubber strap would sit somewhere in the region of the “Shimano” branding on the top the SC-MT800 in your photo). Hopefully that’s clear what I’m trying to achieve.

Thanks for offering to try measuring the gap! :slight_smile:

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I’m running an MT800 junction on my TT bike actually. Using an out front mount stem face plate adapter I picked up off of eBay from a Japanese seller.

eBay is being difficult on my phone right now and won’t let me open the exact item in a webpage (it keeps directly opening the mobile app). Here is the search results page:

When I bought it shipping wasn’t so crazy expensive though.

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I think you’ll be fine :wink:

(yeah… I know… those bolts… this is my old/previous bike ;))

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Interesting positioning of the display! I have a Bolt directly ahead of the stem so on my bike that space is occupied.

What an absolute star you are, Terry :smiley: - very many thanks for going to the trouble of testing that out and uploading the photos. :+1: :+1: :+1:

As you suggest, it looks fine to me (and worst case I’d use the 35mm mount with a shim to generate a larger gap).

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Quick question @loxx0050: when you shift gears does the gear number on the MT800 display change instantly or is there a delay of some sort?

No delays. It changes immediately when you press the shift buttons. I wanted one of these so I could easily display battery charge level without having to remember the flashing lights codes with the other junction boxes.

Also it is handy when adjusting the derailleurs as it shows what position you are at in the range so you can keep notes without having to hookup directly to a laptop using the etube software.


Neat. But, I don’t know that I would get it if I already had the wireless unit. With the wireless unit my garmin can show all that info too.

@terry_bettershifting, I finally got the MT800 display fitted, and the silicone strap for my bar-mounted light does fit OK!

I’m a fan of this display; for those who like to keep their “cockpit” clean (ooh err) then a RS910 bar-end junction makes more sense, but if like me you don’t mind having a few gadgets on the bars then one of these Di2 displays, combining junction box/wireless unit, is a good alternative. I like seeing the battery level, gear num (& shift mode) without resorting to fields on the bike computer etc.

FWIW I see that Mason has fitted one of these (the XTR variant) onto their Bokeh Ti Di2 GRX builds.

Q. for anyone who’s used one of these for a while: if you up the period of time that the display is lit up for following a gear change, do you have a feel for whether this put a major, noticeable dent in battery life? I’m guessing it might well do…

NB I also see that Shimano released a new version of the E-Tube Project app last month, which is a big improvement on the old one (usability-wise).

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That’s looking good! Fit pretty well :).
I’ve had it on my bike for a couple of months and didn’t notice any increased battery usage - it probably depends on what you set the screen timeout to though.

Regarding E-Tube 4.0.2 - it does look a lot better, but it has a couple of bugs. The most important thing is: check whether or not your bike still shifts after disconnecting the e-tube app.
If it doesn’t, the bike is still connected and your battery will drain in a day or so. The workaround is to simply connect to the bike again and then disconnect. :slight_smile:

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First hand experience with this. :rage:

Yeah… think I’ll make a page on E-tube 4 bugs sometime this weekend :x

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