12 speed Di2 rim brake wired only. Why?

The title says all. Why does Shimano offer 12 speed Di2 as wired only for rim brake iterations? are there engineering, design etc. constraints that prevent it?

Just recycled old stuff I think


Hydraulic rim brakes. Is that what you mean?

They mean the disc version is wireless between the shifters and derailleurs. The rim brake version still has a wire from the shifters to (I assume) a junction box, to which the derailleurs are also wired.

Standard cable actuated rim brakes i.e. not hydraulic.

So why is it wired?

The explanation seems plan to me: Punishment to people that don’t want the New Hotness. You go disc or you are a Luddite and you will wear the wires of shame. (I have a freshly neutered dog sporting the ‘cone of shame’, and he’s bashing that into everything)


If I had to guess, adding wireless would require designing a new brifter, when there are fewer and fewer people riding rim brake bikes.

Reusing the old design really only requires a software update. And it already works just fine.


Didn’t know how literal ‘wired’ was. Hydraulic rim brakes seems like a market missed, but would open a whole new can of pain. (I remember a rim brake system that used the motion of the rim passing between the pads to increase the pressure on the rim, basically locking up the wheel. And a local biker at the university a was at died doing an endo (wearing a helmet won’t save you from everything) into the rails at a railroad crossing in front of a DPS officer, ironically. I heard those brakes were withdrawn shortly after the number of people injured grew long enough. OUCH…)

That ship has sailed……SRAM tried it, messed it up (o-ring issues) and discs passed it by. No chance of revisiting it now.

I still think hydraulic rim brakes were a superior option…at least at first. People were in love with the “feel” of hydraulics, not the disc brakes themselves. Having a hydraulic rim option would have allowed existing frame standards to continue and people could have used their old wheels.

That said, bike design moved on, improved aero for discs and provided a platform for even wider tires.


The mechanical R9200 series and R8100 series levers are rebadged R9100 series and R8000 series levers with a firmware update and new Di2 ports for the EW-SD300 wiring standard.

The primary reasoning cited by Shimano is sinking more cost into R&D and production for a disappearing market segment, especially coming off the back of the pandemic supply crunch, wouldn’t be worth pursuing. If Shimano wanted to offer a more evolved rim-brake 12-speed system, they could absolutely develop one, but there is just not a demand for it, in their eyes.


I think the market would be larger than they think, but yeah, likely not big enough to make it worth their effort. Having ridden during a surprise rain storm, I fell in love with the hydraulic disc brakes I had. I saw too many other riders having issues stopping/slowing with their rim brakes, and al least 2 accidents that likely were due 100% with brake contamination with ‘water’. The switch to hydraulic brakes shined like a noonday sun, bright and amazing in all that mess.

And who would think that hydraulic rim brake calipers would be compatible with cable caliper mountings? If anything the bike industry has plenty of examples of the fad of standards.

How about they are focusing development on the disk brake version (thus wired → wireless) and putting nothing into the rim-brake so you just get existing technology (wired)? Nothing to do with punishment or shaming, just where they choose to invest product development money.

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I had a LBS also mention they had issues with the bitter coating of Duracell button batteries. Who knows.

As a 12 speed Di2 rim brake owner, I honestly don’t care one bit. It’s one less electronic I have to deal with while out riding. If the shifting stops working, I can troubleshoot a loose wire.

I don’t want an integrated cockpit, I want to be able to change my bars/stem/whatever whenever I damn well please. Bring on the shame!


I would buy that except it wouldn’t be that hard to do wireless in the rim brake version. The brake wire routing and activation doesn’t take up a massive amount of space. If anything it could mean a more reinforced structure, but I’m sure they could surmount that issue, they just don’t want to. So people refusing to go disc are being punished, in a certain point of view… I wouldn’t call Shimano lazy, but they are saying that rim brakes are dead, and that’s it…

And speaking of disc brakes, I’m looking for 160mm Shimano rotors and am having some issues finding them. Lots of 140’s and 200’s and am wondering if I could use SRAM or Hope rotors since they seem to be available in numerous models and even colors.

Oh, I totally get it. But as soon as disc brakes came out I saw it as a way for the vendors to (extort) bring in more money and make things horribly proprietary. And, yes, heck yes, hydraulics has made things far more complicated and even dangerous. I had a hose break during a race on my fat bike, and lost most of the rear braking and on uneven terrain and slop/mud you bet I used the rear brake a heck of a lot. A traditional brake system wouldn’t have failed like that. It was a Jagwire hose set too and ruptured in the middle of the downtube. But the conditions were such that a rim brake system would have been a safety hazard too. I’m torn, I see the need for disc brakes, and yet it is so much more complicated and introduces means of failure that make quick fixes impossible. But anyway…

Yup…I have SRAM rotors on one of my wheelsets with Shimano brakes.

Just remember that they are not designed together, so there could be some very minor spec issues…see Froome and his whining about disc brake noise from his Hope rotors with his Shimano brakes.

But in general they work just fine.

Except they would have to spend money to develop it, money on the slightly different shifters, etc. To me it is clear Shimano doesn’t want to spend that money. Its not about ‘punishment’, its about a business making a business decision.

Thats coming from someone being pulled kicking and screaming from rim-brake to disc-brake / tubeless / hookless. Or go with a L-Two. Problem solved, maybe…

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It would be ironic if I moved to rotors that were noisier than the rotors I have now. They are ‘contaminated’ and I’ve gotten lots of ideas for cleaning them up, but so far nothing has worked (long term).

That was one issue with my fat bike. When it honks, it draws a lot of attention. The wavelengths involved seem to perfect resonate in that bike frame and amplify them quite a bit. It’s embarrassing… :man_facepalming:t2::roll_eyes::sunglasses:

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I was being somewhat tongue in cheek/sarcastic saying it’s ‘punishment’, but they could do a rim brake version, and refuse to. From a certain point of view, they are ‘punishing’ people that still want their rim brakes. Is it literal punishment? Who knows, but it does seem that way since they ‘could do it’, and haven’t/won’t. I’m sure there are a lot of people that would like a wireless rim brake drivetrain, but they aren’t getting it from Shimano (or anyone else).


Simple and effective.

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