MTB Style Shifter SW-M8050 / SW-M9050 Installation Guide

Published April 8, 2021 by BetterShifting Terry

Have you made the plunge and are you making the step to mountain bike Di2? You’ll have to install at least one shifter, depending the amount of derailleurs you are installing on the bike.

Like with most Di2 components, installing these shifters isn’t hard - you just need to know what to do. This page will guide you through the process.

My MTB only has a rear derailleur (1x11) and a dropper post remote on the left hand side of the handlebar, so I’m installing just the right shifter here - SW-M8050-R or SW-M9050-R. The installation method is exactly the same for the left shifters though.

Also, if you're building a Di2 mountain bike you may be interested in learning how to install your Di2 battery in the fork steerer.

When installed, this is what it’ll look like:

Install the SW-M8050 / SW-M9050 MTB shifter end result

Preparation and required tools

You may have already figured this out looking at the image above, but these shifters are located behind the brake levers. This means that if you have already installed a brake lever and handlebar grips, you’ll have to remove those first.

There is no need to disconnect your brake hose though, just slightly loosen the clamp bolt and slide the brake lever off the handlebar. It can sometimes help to rotate the handlebar slightly as you do this.

Also, I’m afraid the Di2 mountain bike shifters do not support the I-Spec standards, so they don’t integrate nicely with the brake levers. They will fit 22.2 mm - 22.5 mm diameter handlebars.

You will need a 4 mm hex wrench to remove the brake lever and a 2 mm hex wrench to tweak the shifting button locations. A 3 mm hex wrench is used to tighten the shifter clamp band.

Finally, make sure you have an EW-SD50 wire long enough to connect the shifter to your display or Junction A.

With that out of the way, let’s get started

Install the shifter on the handlebar

Take the shift lever out of the box and loosen the clamp bolt slightly. Make sure you don’t loosen it too much, because that can cause the square nut to fall out - and getting it back in can be a pain.

If this happens to you just put the nut back in where it belongs and apply pressure as you screw the bolt back in. The bolt is relatively short and you’ll have to press it harder than you’d think,making sure it engages the threads on the nut.

Install the SW-M8050 / SW-M9050 MTB shifter slide it on

With the clamp loosened, slide the shifter over the handlebar, to roughly its correct position.

The recommended tightening torque is 2 - 2.2 Nm, but I wouldn’t fully tighten it just yet. First slide the brake lever and your grip back on, so that you can decide on the correct position for the buttons.

As you can see in the image above, the position of the Di2 shift buttons is somewhat limited by the brake lever (clamp) position. You can still tweak the button left/right offset though, so I'll do that next.

Position your bike so that you can look underneath the buttons, or simply rotate the entire shifter if your clamp bolt is loose enough.

See those two bolts? You can use a 2 mm hex wrench to loosen the bolts and move the buttons around.

I have actually moved them to the far right in this image above - they are positioned all the way to the left out of the box. There is no best configuration that’ll work for everyone, so just play around with it and see what works for you.

Let’s connect the wire

Yep… I had already connected the EW-SD50 electric wire when I took that photo. How you install the wire actually depends on the handlebar you use and whether or not it supports internal wiring.

The first step is the same for both methods though - you grab that part with the groove in it and pull it right off. Don’t twist it, just pull. You can probably get away with twisting and pulling it, but you’re not meant to - there is a groove on the inside too.

This is what it looks like with the part (cable cap) off:

Pass the wire through the cable cap and plug it into the shifter. You can do this with the Shimano TL-EW02 tool, or just do it by hand. Either method will work.

Now slide the cable cap back onto the shifter and secure that in place. It can only go on in a certain way - there is a groove on both the cable cap and the shift unit.

The Shimano Dealer manual states that the wire connector can get damaged if the cable cap isn’t installed and while I doubt this will happen when you’re just riding along… it probably does add a bit of protection against the plug snapping / twisting / breaking when hitting obstacles like trees or rocks - or anything else you’ll find on a mountain bike trail.

If your handlebars do not support internal routing then this is it for you. You connect the other end of the wire to your display (Junction A) and you’re done! Make sure the wire is long enough - but not too long - and possibly run it along the brake hose if you like.

I used a 150mm wire and that was just perfect. I’m not worried about it being pulled loose by trees, branches or anything else.

Internal cable routing

If you own a Di2 compatible handlebar, chances are pretty good you can route the wire internally. You need a special groove or a perfectly located hole in the handlebar to let you do this, so not just any bar will do.

The PRO Tharsis / Koryak Di2 handlebars support this, but there are probably others too.

Instead of simply plugging the wire into your Junction A and shifter, you route it through the handlebar, into the groove and then slide the shift lever over the wire/groove:

Now just like before, slide the shifter cable cap over the wire and plug it in. Then push the cable cap back onto the shifter. The final step is to push the wire into the cable cap’s groove. This will make it look a lot better.

With the wire routed through the cable cap's groove, this is what it’ll look like:

You can change the button assignments

One of the great things about Di2 is that you can change the button assignments and switch them around if you want to. Personally I found the default configuration to work good for me, but others prefer to shift up/down using the other button.

Changing it around is simple. You can do that using either E-Tube Project for Windows, or using the mobile app. Since most mountain bikes will have a display installed (and thus also BluetoothLE/ANT connectivity), I’ll quickly show you how to do this using the mobile app.

If you’ve never connected your phone to the bike before, read this first.

Press and hold the button on the display until the “C” appears. Now load up E-Tube Project on your phone or tablet, make sure Bluetooth is enabled and connect by registering a new bike or tap an existing bike to connect to it.

Now open the Customize screen and select the shifter.

Changing the buttons around is easy, you tap either one of them, select the new assignment and then tap 'Confirm'. You can automatically set up the other button by checking the "Assign opposite function..." box.

When you're happy with the button assignment you simply tap Apply to save and apply the settings. Make sure you disconnect the bike by tapping the app's disconnect button. If you forget this last step the bike will not longer respond and you need to reconnect the mobile app and disconnect it using the button.

All done!

If anything is unclear or if you spot any mistakes, please leave a comment or send me a message and I'll get back to you as soon as I can.

Are you building a Di2 bike? Be sure to check out the bike building pages as well!

BetterShifting Terry

About the Author - BetterShifting Terry

I enjoy playing with bike tech - both bike building and wheel building, bike maintenance and of course, Di2. Besides writing content and working on the technical side of BetterShifting, I also work as a Software Developer in The Netherlands.

Read more on the About this site page.

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