1 x Drivetrain with Shimano Di2 for Tri Bike ……advice pls

Hi All,

I’m considering a change to 1 x on a Tri bike …am looking for any advice / pitfalls etc –

Currently im thinking of going Ultegra Di2 (just to keep cost down) with right side controls being Di2 shifters

1 x RHS - Pole/Extension Di2 shifter

1 x LHS – Pole/Extension Blanked over

1 x 3 port Di2 Junction Box

1 x RHS Basebar Di2 Shifter & Brake lever unit

1 x LHS Mechanical Brake lever only

1 x Rear Derailier – Ultegra Di2 long cage ….enable an up to 32 tooth I believe

1 x Battery & charger with wires etc to connect

With Chainring …to suit terrain etc ….

Thoughts, feels, advice, recommendations, on this set up ? thanks all!!!

I ran 1x on my tri bike for around a year. It worked well and I enjoyed the simplicity. Bike has since been returned to a 2x (I live in Utah and needed a bit more gear) My was mechanical so I don’t have any input as far as Di2 parts are concerned though sorry… but this sounds like a pretty sweet set up.

I’m also only in the discovery phase but 2 things stick out…

Ultegra GS rear mech now goes to 11-34 and aren’t you going to need a SM-JC41 to link the 3 port junction box, battery and rear mech together.

Keep us posted. Only ordered my frame yesterday and have a 3 month wait for it to be delivered so am avidly reading about new parts for me which are Di2 and hydraulic brakes.

Check Rotor 1x13. They should release it early 2019. With different size cassette’s you can tackle most flat or hilly environments.

thanks all! if i pull the trigger on this project (and i certainly hope to) i’ll keep this thread alive with progress!

thanks - Paul

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Hi Paul, did you do this in the end and if so how did it work out? Have a new TT frame on order and figuring out some build options, something similar to what you were planning sounds like just what I had in mind

Any updates? I’m trying to consider 1x options for my new TT toy.


Built the bike pretty much as planned. 1x SRAM Force crankset. Ultegra Di2 rear derailleur. Di2 shifter on the right hand extension. Di2 3 port junction box hidden in the stem. One port goes to shifter, 1 to the derailleur, 1 to battery in the seat tube.

Very simple to build and use, all works great. I have a 58T chainring and an 11-28 cassette, train and race on fairly flat roads and honestly don’t think I’ve even come close to needing the 28 yet, could probably have got away with a 11-25. Do also have a 52T chainring, so figure if I ever do a hillier course I could put that on with an 11-32 cassette which should work with the same chain length and give me enough gearing to get over some decent hills.

Edit to add: also saved significant money and a bit of weight only needing one shifter, one derailleur, one junction box. And the bike looks very clean for the eyeball aero test which is the main thing!

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Just found this thread, and I am thinking of doing the exact same thing on my TT bike as I only do flat TTs and currently running mechanical, which means it is a pain to adjust anything on the front end without recabling.

Did you use a chain catcher instead of the front derailleur?

I didn’t bother with a chain catcher. Chainring is a wide-narrow tooth designed for retaining chain in a 1x configuration so shouldn’t need it. Ridden some pretty crappy UK roads on it and haven’t dropped the chain yet.

What chainring did you do with? Considering the same setup on my TT bike, have looked at the Aerocoach arc ring which seems like a good solution

I’ve got the Aerocoach arc. Pyramid also have a good reputation.

did you need just one junction box? I am getting a cockpit junction box, but I assume there is also one where the battery goes?

I am running Vision NS aero cranks but I will likely remove the small chainring and get the Aerocoach chain catcher to be on the safe side.

Grand, thanks

Yup, just one 3 port junction box in the cockpit. One to shifter, one to battery, one to rear derailleur. Some quite long wires!

sweet. Actually going to come out super cheap. I was looking at an 11speed Etap, as I thought that was my only option, but they no longer sell the blip box and its also kind of expensive. But actually, I am glad I saw this thread as di2 seems a much better option.

I did this recently with mt new tt bike. I was super easy, I just use the bar end shifters at the moment, I also went with TRP Hydraulic disc brakes (reason was I couldn’t get shimano brakes and shifter set, added bonus is was so much cheaper). Little bit of a pain if you are out of the saddle and need to change gear but it’s ok in the end. If it gets too much of an issue I can add some sprint shifters for not a lot of coin.

Have you seen this before:

I am still working on which 1x set up to go with. I really liked the look of the Aerocoach chainrings, so I spoke to them about those, but they are not compatible with my crankset. I have a Vision NS Modular Aero crankset. I also have a spare SRAM Dub crankset (new version) that I could probably get a BB for to use, but I can’t seem to find compatible 1x largeish (54T) chainrings. My restriction is I am using 165mm cranksets as it really helps me get the power out in the TT position so I have to use those.

Any suggestions / thoughts on whether I could get a 1x chainring for either of those cranks? Looking for Aero. My last resort will probably be just using the existing vision crank with the 52T and removing the inner ring and adding a chain guide.

Hi, great inspirations here. I am also working out a 1x tri set up. It is an old ish Langdale Lightweights frame. I think i am stuck with a BBR60 Ultegra and I have a nice 130 bcd SRAM narrow-wide chainring. But at a total loss as to what cranks to install. Any suggestions? SRAM Force woudl be nice but it needs BB30, right? WHich won’t go into this frame…

ANy help appreciated