So it’s been a while since i raced (13 years) and i am planning on doing ironman again next year - and as such am in the process of putting a bike together. I’m in my mid 50’s so no young super cyclist and want to take advantage of some of the easier gearing options now available. I am going with Di2 in my build and was wondering if there was any reason why any of the new GRX Di2 components would not work with ultegra or durace Di2 - for example… i am looking at running the GRX 810 Crank with the RX 815 Front Deraileur along with Durace TT shiftere s SW9160 and the disk brake shifter combo (ST 9180)…i understand mixing and matching Durace / Ultegra Di2 is fine but will it play nice with GRX Di2?
My understanding is that you need GRX front and rear deraileur, however, you can use GRX or Ultegra or Dura Ace shifters
An Ultegra Di2 is rated for a max RD of 34, but lots of people use it on 36 cassette (I have actually tried this on my gravel bike which was pre GRX). GRX is rated for max 36 cassette, but many people use a 40 cassette (I have not tried this)
I’ve not looked in detail at the GRX FD, it is designed to work with a 46/30 sub compact chainset. I guess it would work on a 50/34 compact too
How low of a gear do you want?
Thanks - yeah i use the ultegra mid cage and run a 36 comfortably on my road bike. So you are saying i should go with the GRX rear rather than Ultegra?..
I understand using a grx crank will require the grx front deraileur but was assuming i could use Ultegra at the back…
I’ve not looked in detail at the GRX FD, it is designed to work with a 46/30 sub compact chainset. I guess it would work on a 50/34 compact too
Slight correction. The GRX810 2x crankset which is designed to work with Di2 is actually a 48/31 chain set.
https://bike.shimano.com/en-US/product/component/grx-di2/FC-RX810-2.html
Why do you want to use a GRX crankset?
Thanks - yeah i use the ultegra mid cage and run a 36 comfortably on my road bike. So you are saying i should go with the GRX rear rather than Ultegra?..
I understand using a grx crank will require the grx front deraileur but was assuming i could use Ultegra at the back…
The way Shimano designed/programmed the Di2 eTube System is you can’t mix and match derailleurs between road and MTB. A GRX front and a Ultegra rear will not work (and vice versa). It’s either all MTB or all road Di2 derailleurs that are to be paired. They really don’t care what shifters though so mixing and matching road/TT shifters with GRX Di2 derailluers should be fine. Take a look at the latest Di2 compatibility chart to confirm.
If you already have a GRX front then you have to get a similar MTB GRX or XT/XTR (I think that is it) to work. But again check the compatibility chart to make sure.
If you already have a GRX front then you have to get a similar MTB GRX or XT/XTR (I think that is it) to work. But again check the compatibility chart to make sure.
That was my understanding also
Thank you - i was not aware of that - most helpful. Any links to the compatibility chart perhaps? i cannot seem to find a current one including GRX…
i am after the 48/31 crank with a stages power meter - i religiously ride to my power numbers and as i’ve gotten older the longer hills like Richter Pass and Yellow lake have gotten longer and harder…lol. By harder, i mean harder to ride the power i want to ride on the climbs without mashing gears
Thank you - i was not aware of that - most helpful. Any links to the compatibility chart perhaps? i cannot seem to find a current one including GRX…
You can get Di2 info from the Shimano e-tube project website, The compatibility charts are posted there too.
Here’s the latest: https://e-tubeproject.shimano.com/pdf/en/HM-CC.3.4.3-00-EN.pdf
I have not used the GRX series yet, but AFAIK they are designated as Di2 Road components so you should be able to mix and match front and rear derailleurs from GRX with any other 11 speed Di2 Road components. The current compatibility chart appears to confirm this is the case.
The only FD and RD mix incompatibilities I know of are mixing Road and MTB derailleurs or mixing 10sp and 11sp derailleurs.
"I have not used the GRX series yet, but AFAIK they are designated as Di2 Road components "
I guess that’s the rub right there - are they road or mtn desingnated…
Thank you for the link
I would think that 50x34 chainrings and an 11-34 cassette would work.
I am 55 years old and ride a Rotor Aldhu crankset with INspider power meter, 53x39 with an 11-28 all the time.
I guess that’s the rub right there - are they road or mtn desingnated…
I think the Shimano chart clearly indicates GRX is subset of their road components. They also have an article from March that covers mixing and matching the GRX and Road systems, but it only included their mechanical components.
There is probably no concern for your proposed setup as in your OP you were asking about mixing tri shifters with GRX. Any Di2 smart (ie contains firmware chip) shifter is compatible with all other e-tube Di2 components.
The only other GRX consideration is that the crankset is matched to the FD because they added 2.5mm outboard offset to clear bigger tires. End result is 5mm increase in q-factor.
I am using Dura Ace Di2 9150 rear derailleur with an 11-36T cassette, which works great with room to spare. I still have a full turn left to go on the B-screw before it maxes out. I’m not using the Wolf Tooth RoadLink or anything like that.