2024 Shimano RX825 2x12 GRX Di2

The spirit of Grav-lo-cross. No but seriously, cyclocross and gravel go here!

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RDY
Posts: 2583
Joined: Thu Jul 30, 2020 10:31 pm

by RDY

No official support for cassettes larger than 36T? That's unbelievably bad. They don't seem to want any of the 1x or wide range electronic 2x market.

Still, at least I can now pay €370 for 105 RD with clutch for road - €100 more than Ultegra.

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frnchy
Posts: 45
Joined: Sun Feb 07, 2021 5:30 am
Location: CO

by frnchy

As expected, a pretty lazy refresh, but GRX has always been quite tolerant of larger-than-official cassettes, so 36t official max ~= 40t max actual; one of my friends runs his 11 speed mech GRX with a 40t cassette with no goatlink or anything and it works fine, so I'm optimistic. I really just want the rear derailleur so I can have a clutch on my gravel bike with the 105 Di2 I have on there currently.

RDY
Posts: 2583
Joined: Thu Jul 30, 2020 10:31 pm

by RDY

"small" 12s gravel cassettes for HG / MS are in the 44-46T range though. Not 40T.

Agent041
Posts: 258
Joined: Fri Sep 08, 2023 11:16 am

by Agent041

Was obviously waiting for nothing. Somewhere on this thread (or similar), someone stated a way lower price, so I was expecting a 105 Di2 level price point and not Ultegra. So I will go 105 Di2 to upgrade my gravel bike.

Agent041
Posts: 258
Joined: Fri Sep 08, 2023 11:16 am

by Agent041

RDY wrote:
Thu May 23, 2024 5:55 pm
No official support for cassettes larger than 36T? That's unbelievably bad. They don't seem to want any of the 1x or wide range electronic 2x market.

Still, at least I can now pay €370 for 105 RD with clutch for road - €100 more than Ultegra.
Is there even 105 Di2 rear derailleur with clutch?

kitchencity
Posts: 100
Joined: Thu Jun 24, 2021 9:06 pm

by kitchencity

https://bike.shimano.com/en-EU/product/ ... 50-12.html
...I wonder if they'll just this firmware compatible for 1x

TheBelgian
Posts: 180
Joined: Wed Apr 26, 2023 9:09 am

by TheBelgian

Agent041 wrote:
Fri May 24, 2024 6:26 am
Was obviously waiting for nothing. Somewhere on this thread (or similar), someone stated a way lower price, so I was expecting a 105 Di2 level price point and not Ultegra. So I will go 105 Di2 to upgrade my gravel bike.
I'm running 105 Di2 on my gravel bike (which I only use on the road because we have very very bad roads here), but I'm interested in a GRX RD for the clutch. Had it happen once here that my chain jumped 4 gears at the back when hitting one of the many potholes we have (in winter I ride a lot in the dark).

TobinHatesYou
Posts: 13009
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

RDY wrote:
Thu May 23, 2024 5:55 pm
No official support for cassettes larger than 36T? That's unbelievably bad. They don't seem to want any of the 1x or wide range electronic 2x market.

Still, at least I can now pay €370 for 105 RD with clutch for road - €100 more than Ultegra.

36t on the low end would be okay if they just introduced Microspline Road and a 10t cog.

As for 1x, well we know the fully wireless, external battery MTB Di2 RD is coming.

LainOTN
Posts: 85
Joined: Sat Feb 15, 2020 3:01 pm

by LainOTN

I'm a bit puzzle about the levers, they claim it have 1 SD300 satallite port and another SD300 e-tube port, like the ultegra levers

https://bike.shimano.com/en-US/product/ ... 825-L.html
https://si.shimano.com/en/ev/ST-RX825-5053

But the manual says that only wireless.?? and the e-tube port is only for pc linkage...
https://si.shimano.com/en/dm/GADBR10/in ... trol_lever
The ST-RX825 is for wireless gear shifting only. It does not support wired gear shifting.

What?!?!? Is not that a bit stupid?

I was hopping to run this totally wired due the ammount of advantages it gives to me. Consider running ultegra levers...

RDY
Posts: 2583
Joined: Thu Jul 30, 2020 10:31 pm

by RDY

TobinHatesYou wrote:
Fri May 24, 2024 10:00 am
RDY wrote:
Thu May 23, 2024 5:55 pm
No official support for cassettes larger than 36T? That's unbelievably bad. They don't seem to want any of the 1x or wide range electronic 2x market.

Still, at least I can now pay €370 for 105 RD with clutch for road - €100 more than Ultegra.

36t on the low end would be okay if they just introduced Microspline Road and a 10t cog.

As for 1x, well we know the fully wireless, external battery MTB Di2 RD is coming.
Not really if you want to run a 50/34 and you're not either incredibly strong or light. A lot of people are running that with 11/40/42 and even up to 11/46 currently. No chance of the former as no casettes exist in that range for 12s (except Rotor - which supposedly only works with their transmission), and for the latter I think 11/44-46 will be beyond the capabilities of this RD.

I guess we can wait for WolfTooth to make a 2x compatible cage with up to 11-45. Since I can't imagine they won't do it. But it sucks that Shimano seem to be throwing in the towel on this.

OtterSpace
Posts: 380
Joined: Sun Mar 08, 2020 6:28 am
Location: California Silicon Valley

by OtterSpace

Has anyone who has ridden GRX and Shimano road please chime in on if they feel any braking power and modulation differences? I'm a bit of a crazy person looking for the best braking performance and currently use a 180mm front rotor with a Campag caliper and Ultegra shifters so I'm open to changing to GRX shifters.

I ask about the braking performance because the piston link arm path on GRX is much closer to MTB vs road for servowave.

Also how have people found GRX shifter ergonomics compared to shimano road shifters for flaired bars and is the grip surface on the shifter blade a minor feature or a real improvement?

pushpush
Posts: 365
Joined: Wed Feb 01, 2023 5:10 am

by pushpush

I live in a mountainous area. I regularly do climbs that are only just barely possible on a 34:51. I'm pretty strong. I need 2x and a big cassette to be able to climb fire roads and also be quick enough on the road.

The lack of support for mtb wide gearing seems like a huge miss.

I hate to say this. I swore this wouldnt happen. -- My next build might be sram even though I hate their brakes.

TobinHatesYou
Posts: 13009
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

RDY wrote:
Fri May 24, 2024 1:48 pm
TobinHatesYou wrote:
Fri May 24, 2024 10:00 am
RDY wrote:
Thu May 23, 2024 5:55 pm
No official support for cassettes larger than 36T? That's unbelievably bad. They don't seem to want any of the 1x or wide range electronic 2x market.

Still, at least I can now pay €370 for 105 RD with clutch for road - €100 more than Ultegra.

36t on the low end would be okay if they just introduced Microspline Road and a 10t cog.

As for 1x, well we know the fully wireless, external battery MTB Di2 RD is coming.
Not really if you want to run a 50/34 and you're not either incredibly strong or light. A lot of people are running that with 11/40/42 and even up to 11/46 currently. No chance of the former as no casettes exist in that range for 12s (except Rotor - which supposedly only works with their transmission), and for the latter I think 11/44-46 will be beyond the capabilities of this RD.

I guess we can wait for WolfTooth to make a 2x compatible cage with up to 11-45. Since I can't imagine they won't do it. But it sucks that Shimano seem to be throwing in the towel on this.

Why would you run a 50/34x10-36 on gravel though? Hardly anyone needs 5:1 at the top end. 46/30x10-36 is equivalent to running 50/34x11-40 except you actually have extended range on both ends.

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pdlpsher1
Posts: 4165
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

James Huang at EC seems to think that 1x represents 70-80% of the gravel market? In my circle of friends there are more 2x than 1x. I honestly think 2x has its place and won't disappear anytime soon. A couple YouTubers that I follow (Jom at Gravel Cyclists and Ben Delaney) ride 2x on their personal bikes. They are certainly strong riders. It seems that Shimano wants you to go with a mullet 1x if you need a very low gear. Personally I'd like to see a 2x wide range cassette (11-40 being my favorite) but I think there are technical challenges with that. A wide range cassette need an offset upper pulley so that the pulley will track the shape of the cassette closely. The problem is that an offset pulley can only work well in a 1x setup since the amount of offset is determined by chain slack. I know that many people have run 11-40 in a 2x setup. I'm one of those. But I also know this setup doesn't work good enough for some people due to bike geometry differences. So it's not reliable enough for Shimano to offer it as an option is my guess. A longer cage solves the teeth capacity issue but it doesn't solve the B-gap issue. Shimano has made a wide-range cassette work in a 2x but that was a MTB setup, one with a small front chainring tooth difference. The 17T chainring gap on the GRX is just too large for it to work. One option is to shrink the chainrings (45/28) to work with a 10-36? At this point I really don't see Shimano doing anything to address the needs of those wanting wider gearing. So I plan to stick to my 11-speed GRX Di2 group for gravel, which is working very well running a 12-speed chain, 48/31 12-speed chainrings, and a 11-speed 11-40 XTR cassette.

Here are the bikes of two of our local Cat1 gravel racers, Zack and Whitney Allison. Pic shown is Whitney's bike. Zack's Mog build is identical to Whitney's.

Image

by Weenie


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TobinHatesYou
Posts: 13009
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

pdlpsher1 wrote:
Sat May 25, 2024 5:35 am

Here are the bikes of two of our local Cat1 gravel racers, Zack and Whitney Allison. Pic shown is Whitney's bike. Zack's Mog build is identical to Whitney's.

Image

This is some serious survivor bias reasoning. 100% of sponsored GRX Di2 users are on 2x because that’s the only option they really have.

They were running 2x11-speed Di2 GRX until now, preferring it over 12-speed mechanical in either flavor. In other words they had to make a choice between electronic shifting and that 12th cog and chose the former. Without Di2, they clearly won’t choose 1x12 either especially when Shimano doesn’t have its own XPLR equivalent.

I think we’d get better insight looking into how the SRAM riders have sorted themselves. How many are on “2x Road Wide,” how many are on XPLR and how many are on mullet builds. Over here most self-spec SRAM dropbar dirt builds are mullet despite complete bikes from major brands predominantly being spec with XPLR, but west coast gravel is basically XC.
Last edited by TobinHatesYou on Sat May 25, 2024 9:27 am, edited 3 times in total.

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