GRX 12s Di2 RD-RX825 derailleur Real weight, 1x plans & how to save 5 grams 🪶
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- Опубликовано: 28 авг 2024
- Starting up an experiment to get my Gravel frame up and running again, with goal of finally going back to a 1x setup. Like many of you I was disappointed to see that Shimano's 1X version of Di2 GRX is yet to be revealed, and since we probably won't see that this year I decided to pick up the 2x RD-RX825 derailleur and see how far we can push it in a 1X setup.
But first, here's the initial first look, real weight, and some comparisons, and a few potential tweaks.
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Although I would not recommend it ;-) if you use cage from XT, XTR, or RX817 it would allow for better shifting (no pun intended) Those 3 derailleurs are the exception in Di2 family, because guide pulley is offset behind the A-pivot. This will allow you to clear 42t sprocket without compromising shifting in the smaller sprockets. Keep in mind that beyond 36t Di2 servos have very different internals with chunky gearbox and 'one-way coupler'. It will work but motor longevity will be significantly decreased.
Yep, noticed that when I did the same thing with the 11speed version :) once the battery got below 50% I stared to struggle hehe.
This will just have to keep me occupied until we have the 1x version next year. Really crossing my fingers for an xtr version 😆
Cheers mate for the knowledge as always 🙏
Mmm, better shifting!🎉
Keep up the great work, Tobias. This channel itches my 'wanna design and build another bike' scratch while unable to justify it right now. 😅
I had a feeling you gonna do this… This is awesome!
Noice. Thanks for taking the time, looking forward to seeing what your experiments will bring. Good luck!
Gotta say, the 12 speed GRX derailleur does look way nicer than the 11 speed IMO
You can lop off about 40g by removing the lower pulley and cage. Plus you'll need less chain
Pro tip: SRAM has a really nice line-up of 1x 12 speed components... 😉
Sea…m? Never heard about it! 😜
@@slayerofgrams SRAM. like GRAM. But with an S ;)
I'm sure you know 2x grx can unofficially clear 11-40t no issue. With the wolfooth road link, the info I've seen is max now becomes 11-42t(or 10-39t if you have one of those Rotor cassettes).
Yep, I’ve run 11-40 unmodified myself on the 11speed version (you can see it on my trek build in the Roj channel)
I’ve also seen people doing un-modified 11-42. As well as people doing 2x with a 11-40 cassette.
Just curious to see if I can squeeze in something bigger with this. It might fail miserably though and last resort would be the rotor 11-39… but that cassette is crazy expensive 😅
@@slayerofgrams I have it setup 2x with 11-40. I think the rotor cassette is 10-39t not 11-39.
@@Alex_564 the 13speed is 10-39, the 12speed one is 11-39 if I remember correctly.
@@slayerofgrams oh I thought I saw a 12spd one starting at 10, but you are correct. Too bad it doesn't look like the 10 can be taken out to replace the 11t.
@@slayerofgrams I tried to install 11-40 unmodified, but that didn't feel mechanically sound, the tension screw doesn't have much to press against any more. With the Wolftooth I now even run 2x 11-42 on one of my wheels sets and while it's certainly pushing it, it works. 2x 11-40 is flawless.
Have you thought about replacing the P-Tension Spring in a dura-ace derailleur with one from a mtb derailleur, presumably with a stiffer spring. Someone on reddit in /bikewrench suggest that a RD-M7xx era Deore XT spring would work. You still would not have a clutch but I bet you would never drop a chain unless you went over some really rough ground. Anyway I have a SHIMANO XTR RD M985 Rear Derailleur P-Tension Spring on order to see if it will fit in my di2 12spd rear derailleur and how it works. Look forward to see the results of your experiment. And all this BS because Shimano thinks the market for 1x GRX Di2 is too small to bother much about.
I’ve been looking into that as I’ve been experimenting with this derailleur a bit now (and unintentionally broke the spring 🤦♂️)
I have not looked up the DA spring specifically, but the bottom “hook” of the spring is different between some of the derailleurs, but as long as you match that part should totally be doable.
For the riding I do I don’t see me using the clutch that often on this GRX, is way stiff turned off anyway. Good to have the option though.
And spoiler for the main channel video, you can use this RD for 1x no problem with the road link DM (10-45 cassette)
Hi! When will test of DM link and max cassette come? Plan on testing 10-44 XPLR? What options on 12s cassettes over 39? (Rotor). Ideally 10-40 12s would be good....
I am using 11speed GRX Di2 with 46-30 front and 40 cassette in the rear - without any further helping parts ...
On my CX bike, I also have a 1x-specific derailleur, the GRX 820 with a 11-36 cassette. It actually is sufficient on most rides, except for high speeds, as I only have a 40T chainring. I am wondering though why the GRX 825 didn't come in a 1x-variant. At some point I hope to upgrade to a wider range with the GRX 822 derailleur. Currently I am wondering whether to go Micro-Spline, or to stick with the HG freehub body.
1x is coming just not yet. Rumors point to a shared design of the yet to be released MTB di2 where we have the di2 battery on the derailleur itself which makes sense for 1x and bikes that often have dropper seat posts where batteries can’t be mounted.
Now, that doesn’t mean we can’t squeeze out a bit more from the the rx825 ;)
If you want the crispiest shifting with cassettes bigger than 40t, I’d say microspline is a safe bet.
@@slayerofgrams Oh that sounds like an actually interesting update!
Damn, so changing the freehub body (thx for also making a weight comparison there!) will likely be added to my list of future expenses. My first step however might be to get a bigger chainring though. Who knows, maybe I go all in and get the Garbaruk microspline 12-speed cassette right away as well. (Don't tell my fiancé!)
There's lots of murmuring online using the Dura-Ace tension arm on other derailleurs. Maximum weight savings!
Woo, link?
@@thedownunderverse weight weenies, something like 40gr savings!
when the 12 speed mechanical dropped, they touted you could swap the cages but the body was all the same. I don't see why this Di2 version would be any different. Swap that medium cage with the longer one and I bet it clears a 52
As mentioned in the video changing the cage alone will only increase the chain clack capacity, it will not change the geometry or how big cassette it can clear (max b-screw position) that’s what the road link is for. However I’m pretty positive it can clear a 40-42 cassette without any modifications like the 11speed version could. Again I won’t have the optimal geometry to move between the small cog to the big, but hopefully it will work well enough. Time will tell 👍
@@slayerofgrams Garabaruk makes cage & pully mods that allow the 1x to clear more cassette. It doesn't change the geo. In theory that mod could be done with a longer Shimano cage & pully combo that compatible. Seen people do that with their older Sram GX 1x11 by swapping in a newer GX 1x12 cage to get bigger 10-50t cassette to work.
The GRX 1X is confirmed to launch by 2025 😎💯
Not "officially" confirmed but it's a know secret so to speak. 2024 is out in either case :)
@@slayerofgramsfor sure? No GRX 1x12 Di2 until next year?
How does that cage length compare with the 105 Di2 cage?
Don’t know sorry
@@slayerofgrams if you can measure the distance centre to centre of the jockey wheels , and post here , I’ll do the same on a 105 Di2 RD. I’m guessing they are the same as the 105 which is also rated to cope with the 36t cog (and likely up to 40t).
@@thedownunderverse will do when I’m back home tonight 👍
@@slayerofgrams me too!
@@thedownunderverse looks like it’s around 103mm
2x with wolftooth link far not so good as specific 1x derailleur. I would not recommend it