merlinextraligh

Yes, sortof.

You can use the XTR with road shifters and get it to shift a triple. Problem is that you need to use the XTR FD, which is optimized for MTB chainrings. So if you want to run a 42-32-24. It will work.

But it's not designed to shift to a 52-53 tooth chainring.

The better answer is stay with Ultegra Di2, which will shift up to a 32 tooth cog, and if you need lower range than that, you can do the K Edge modification to the rear derailleur, and go as big as a 40 tooth cog.

merlinextraligh

Stock Ultegra is spec'd for 32 teeth, and Shimano is always conservative about their capacity ratings, so it will shift a 34 tooth cog.

And why don't you like the K-Edge. All it does it swap out the cage for a longer cage, with the top pulley moved back.

We've got Dura Ace Di2 with the K-Edge adaption on our tandem. We're only running an 11-25 on it now, but it shifts great, with no discernable difference from a stock derailleur.

Cyclist0108

Di2 will do a triple, and the road shifters are just buttons, so quite possibly ....

The XT(R) triple is 40-30-22T, so I am not sure that I would want to do that, but it sounds like it could be done.

corrado33

Honestly, I don't think hacking the DI2 would be hard at all. I bet the steps are stored in some memory on the device and it just moves a tiny stepper motor or servo to those positions every time you push the button. Modify the steps and BAM, you've got yourself a triple capable DI2 setup. Even if you CAN'T modify the memory (non rewriteable), as long as you could interface with the motor controller you could make the derailleurs move wherever you wanted them.

With the hardware, even I (a relative electronics newb) could program a tiny micro to do what you want. I bet the limitation for making something like this was the force needed to push the derailleur one way or another. (And making it reliable.)

Cyclist0108

I think the problem, at least from Shimano's own point of view, is the FD and RD are designed to work together, and their (evil windows-only) software won't recognize the mix, at least according to the link I posted. The rear moves a little bit to fine-tune the shift when you change sprockets in the front. Reprogramming the firmware in such a way that the components are still recongized by each other isn't trivial.

Since the large sprocket of the XT(R) triple is only 40, it might be more practical and cost-effective to use say a 38-28T double. (FWIW, I am considering these options due to some lingering issues from an ankle break that make it hard to stand up on the pedals on really steep climbs).

corrado33

Oh I wasn't talking about modifying the firmware. The interaction between the derailleurs is easy. It's simply another servo. Every time you press the button it shifts BOTH a bit. So instead of having one set of numbers for the RD shifts, you have two, one set for the RD motor, and one set for the FD motor. Again, provided the steps are stored in memory and not in the firmware itself, it'd be an easy modification. If it's hard programmed in, it'd be more difficult, but certainly not impossible. At that point I'd simply write my own program to directly interface with both the FD and RD.

Heck, I don't know how these things actually work, but if it were me I'd program the derailleurs (especially the FD) to move a bit more than required for the shift, then move back after X amount of time to facilitate quick shifting. I'd even add "adjustment" buttons if, for some reason, the shifting was weird you could modify the motor positions for each gear on the fly. (Say if you bent your derailleur during a race.)

Sorry, I didn't mean to derail the thread. I get excited when people combine my hobbies. (Bikes and electronics.)

gsa103

Di2 already does these things. The slight over-shift followed by a delayed trim is normal. Di2 has a fine tuning mode accessible on-the-fly if you need a micro adjustment after a wheel swap for example.

JakiChan

Well, among other things, they don't make it anymore.

That being said, I'm probably strong enough now that I would be fine with an 11-32. At the moment I'm only waiting to see the disc situation sort itself out.

merlinextraligh

Ultegra Di2 6870 GS is spec'd to handle 32 teeth. I'm pretty certain they still make it. It certainly is widely available.

Shimano Ultegra Di2 6870 GS Rear Derailleur 11-SPD

JakiChan

Sorry - I meant that I don't see the K-Edge RD mod on their website anymore. Stock 11-speed Ultegra will be what I probably do, however.

grissley

Hi guys
Let me dig this thread out - maybe sth has changed since it was created?
There is already a triple front Di2 derailleur (XTR FD-M9050) on the market - would it be possible to make it working with a 3x Tiagra crankset?
I got a GRX 815 setup and this 2x I really hate
Problem is, FD-M9050 is designed to work with max 18 teeth cranks difference, being 40 the biggest one and the middle one 10t smaller than the biggest. Effectively, it is designed for 22-30-40.
Tiagra is 30-39-50, so the biggest crank is 10t bigger than XTR is designed for, total difference is 20 (instead of 18), biggest-middle diff is 11 (instead of 10), and the chain line is different, I guess. Do you think there is any option to hack or mod it somehow to make it work together?
Or maybe you have some other ideas on how to create a 3x Di2 GRX-based setup today?
Maybe just replacing the cage in M9050 would be enough (assuming it is easy - I got no idea...)?

grissley

After some thinking on it - I see guys are successfully forcing this derailleur to work with road 3xs, but there is some craftsmanship needed. Still trying to recognize how to make it step-by-step (and with the parts available in Europe), but I just noticed that XT FC-T8000 crankset has the same chainline that the one dedicated to the XTR derailleur in question. Does it mean that this crankset would work with FD-M9050 without any extra artisany? Any ideas?

Kimmo 

Well designed FD cages which shift reliably, especially triple ones, are extremely refined and subtle bits of design. They need to be sized for the rings they'll be shifting within like 3 teeth max IMO. Only way to make it work is to graft on an appropriate cage.

Polaris OBark

If this gearing is what you are looking at for a triple, you can get very close for US$150 with a GRX 46/30T. I'm using it with a first-gen Ultegra Di2 front (and rear) derailleur, along with an 11-36T and 11-34T cassette, with no issues. This would save you a lot of money and headaches.

grissley

I do have 30-46 right now
And I hate it each time i need to move from 46 to 30. It takes too much time and it always happens during climbing, but in the moment when I still got some speed that I wouldn't like to loose. Anyhow, by the moment I reduce 46 to 30 and then move two cogs down on the cassette, I need to spin like crazy for like 1.5 rotation and loose all my speed - and need to go to the lowest gear right after anyhow. Partly it is Di2's fault, as it changes the gears sequentially (on mechanical setup i was pressing both buttons on the same moment and reduction on the cranckset was taking place on the same moment as 1gear reduction on the cassette. This was waaay more efficient than what I got now). But I guess the reason it takes so much time is also in the big size difference between the rings - 16T. And yest another factor - having a 3x set I would spend majority of time on the middle one, having somehow "middle ring + 2 extra gears on both sides". With 2x I need to change the front ring in the middle of my most commonly used range.
It seems a challenge to have a 3x on Di2 though (adapters, FD and RD replacement, different chain lines, different axis lengths /if FC-T8000 was to be used/ etc). So just theorizing. Maybe I would still try replacing 12-30 cassette with 12-32 instead, or putting oval rings on the front "just to check", or I don't know, maybe I would get used to with a time. Anyhow, it simply pisses me off that having moved from 3x Cross XT setup (with a road cassette, though) to far more advanced and expensive Di2 on a new bike I am simply less happy than I was before.

DaveSSS 

Some folks need to learn how and when to shift. I ride many steep hills and the Colorado mountains. I use a shimano grx 48/31 or 46/30 on my sram force axs 12 speed bikes. I use the big ring as much as possible. I can ride slopes of 5-6% in the big ring, but only if I chose to pedal standing. I often pedal standing until the slope becomes too steep, then sit and quickly shift to the little ring. No compensating shift is then required. I rarely shift to the little ring unless I'm already using a high torque, so there's never any wild spinning involved. If you're not pedaling with a high torque, but choose to switch to the little ring before it's needed, shift at least on sprocket smaller first, then shift to the little ring and make the second sprocket shift. No wild spinning occurs.