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GRX Di2 shifters + RS785 brakes (post-mount)

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GRX Di2 shifters + RS785 brakes (post-mount)

Old 03-06-21, 02:41 PM
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GRX Di2 shifters + RS785 brakes (post-mount)

I've got a 2016 Diverge which is post-mount. Anyone know if the GRX Di2 shifters will work with RS785 brakes? The Shimano compatibility tool says they are compatible, but the spec sheets for the shifters and levers call for different brake hose kits.

GRX Di2 shifter - SM-BH90-JK-SSR brake hose
RS785 calipers - SM-BH59-J-SS brake hose

Anyone using this shifter + caliper combination?
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Old 03-06-21, 04:01 PM
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In my experience, all of the two-piston Shimano calipers are interchangeable.

The RS785 calipers are re-branded XT, so if they work with XT, they will work with those.


(Also, FYI: You can get the RS785 calipers along with the Di2 shifters for $250 at Universal Cycles. (I bought a backup set when the price briefly dropped to $199).)

Last edited by Cyclist0108; 03-06-21 at 05:35 PM.
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Old 03-07-21, 08:59 AM
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Originally Posted by wgscott
In my experience, all of the two-piston Shimano calipers are interchangeable.

The RS785 calipers are re-branded XT, so if they work with XT, they will work with those.


(Also, FYI: You can get the RS785 calipers along with the Di2 shifters for $250 at Universal Cycles. (I bought a backup set when the price briefly dropped to $199).)
Wow that is tempting. It'd also allow me to reuse my brake lines saving another $60. I know GRX Di2 is good, but $450 better?
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Old 03-07-21, 06:22 PM
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I don't have GRX, but I think the main difference is the pivot point is supposed to be more ergonomic for folks who ride the hoods.

I ride the hoods on the RS785 and they are the most comfortable brakes I ever had.
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Old 03-12-21, 06:37 AM
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Originally Posted by vinuneuro
Wow that is tempting. It'd also allow me to reuse my brake lines saving another $60. I know GRX Di2 is good, but $450 better?
Yeah, other than ergonomics all Shimano Hydraulic brakes are interchangeable and will work with one another. I really wanted the new GRX di2 hoods and brakes but like you said, the upgrade is quite expensive so I went with Ultegra. The different brake hose kits are for the caliper end because the XT and I believe all post mount have a banjo fitting where the newer flat mount calipers like the GRX's have a straight threaded fitting. Just re-use the hose you have and all is good!
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Old 03-12-21, 07:22 AM
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Originally Posted by vinuneuro
Wow that is tempting. It'd also allow me to reuse my brake lines saving another $60. I know GRX Di2 is good, but $450 better?
The GRX Di2 brifters cannot be bought. Shimano has missed every restock promise since August 2020. And the GRX Di2 lineup is part of that. If it isn't in stock now you're not going to see it until next year at soonest.
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Old 03-12-21, 03:41 PM
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I have a bike with GRX shifters and XT post mounted brakes.
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Old 03-13-21, 08:32 AM
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Originally Posted by Marcus_Ti
The GRX Di2 brifters cannot be bought. Shimano has missed every restock promise since August 2020. And the GRX Di2 lineup is part of that. If it isn't in stock now you're not going to see it until next year at soonest.
You correct that they are hard to find. Merlin has the whole 2x GRX 815 Di2 groupset in stock right now.

https://www.merlincycles.com/en-us/sh...eid=4e44856289
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Old 03-13-21, 08:37 AM
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Originally Posted by Bryan C.
You correct that they are hard to find. Merlin has the whole 2x GRX 815 Di2 groupset in stock right now.

https://www.merlincycles.com/en-us/sh...eid=4e44856289
'Whole groupset'...other than that very page which shows they don't have brake rotors, and only a single size of one gearing of crankset.

And, of course, presuming Merlin even ships Shimano to the USA anymore.
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Old 03-13-21, 08:37 AM
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Originally Posted by vinuneuro
Wow that is tempting. It'd also allow me to reuse my brake lines saving another $60. I know GRX Di2 is good, but $450 better?
I would have to say the GRX Di2 levers really are that much better. The braking power is definitely an improvement over the DA 9120 brakes on my road bike, which are supposed to be better than the RS785 levers. If you can find them I wouldn't hesitate on buying them.
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Old 03-13-21, 08:39 AM
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Originally Posted by Marcus_Ti
'Whole groupset'...other than that very page which shows they don't have brake rotors, and only a single size of one gearing of crankset.

And, of course, presuming Merlin even ships Shimano to the USA anymore.
They do ship shimano to the US. Did you really expect every option to be available right now?
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