GRX 11 to 12 speed upgrade

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tihojla
Posts: 1
Joined: Wed Mar 13, 2024 9:50 pm

by tihojla

Hello everyone,

my question is, what do I need to upgrade to GRX 12 speed from 11 speed.

My current setup is GRX 11 - 810, 2 chainrings 48/31, XTR 11-40 cassette.

Can I buy only right 12 speed GRX 820 shifter, 12 speed chain, and a new 12 speed cassette (11-36).
Will it work?

by Weenie


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warthog101
Posts: 977
Joined: Wed Sep 25, 2013 10:05 am

by warthog101

I think the cable pull ratio has changed.

That said, they do use a revised cable pull ratio, that according to Shimano, is officially not cross-compatible with 11-speed road or Shimano’s MTB 12-speed components

https://escapecollective.com/shimano-gr ... s-on-look/

Sounds like the 11s derailleur wont work with the different 12s pull ratio.

Treptay
Posts: 77
Joined: Sun Sep 06, 2020 11:23 am

by Treptay

warthog101 wrote:
Mon Mar 18, 2024 11:58 am
I think the cable pull ratio has changed.

That said, they do use a revised cable pull ratio, that according to Shimano, is officially not cross-compatible with 11-speed road or Shimano’s MTB 12-speed components

https://escapecollective.com/shimano-gr ... s-on-look/

Sounds like the 11s derailleur wont work with the different 12s pull ratio.
Funnily enough, the 12s derailleur apparently works on 11 speed fine
https://www.youtube.com/watch?v=dEEe0hIMpf0

warthog101
Posts: 977
Joined: Wed Sep 25, 2013 10:05 am

by warthog101

Treptay wrote:
Mon Apr 01, 2024 12:18 pm
warthog101 wrote:
Mon Mar 18, 2024 11:58 am
I think the cable pull ratio has changed.

That said, they do use a revised cable pull ratio, that according to Shimano, is officially not cross-compatible with 11-speed road or Shimano’s MTB 12-speed components

https://escapecollective.com/shimano-gr ... s-on-look/

Sounds like the 11s derailleur wont work with the different 12s pull ratio.
Funnily enough, the 12s derailleur apparently works on 11 speed fine
https://www.youtube.com/watch?v=dEEe0hIMpf0
There you go then!

DawnBat
Posts: 20
Joined: Thu Aug 24, 2023 1:22 am

by DawnBat

This video is the R7120 STI with R8000 GS RD
Shimano 105 12 Speed Groupset With 11 Speed Rear Derailleur
https://www.youtube.com/watch?v=9u6ntnyw5vQ

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Kurt1980
Posts: 339
Joined: Mon Oct 26, 2020 9:41 am

by Kurt1980

Chasing this up as I also am looking to upgrade. My question is about chainrings specifically... will my existing 11 speed GRX chainrings work with an otherwise completely 12 speed GRX groupset?
Cheers.
Edit: It seems as though 12 speed chains still retain the 2.18mm internal width, but wondering if anyone has real world experience they can draw on.

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

by frnchy

Kurt1980 wrote:
Sun May 26, 2024 3:50 pm
Chasing this up as I also am looking to upgrade. My question is about chainrings specifically... will my existing 11 speed GRX chainrings work with an otherwise completely 12 speed GRX groupset?
Cheers.
Edit: It seems as though 12 speed chains still retain the 2.18mm internal width, but wondering if anyone has real world experience they can draw on.
Not GRX, but my 105 11 speed rings worked perfectly with a Shimano 12 speed chain. 11 speed chainrings + 12 speed chain was also popular with the pros roughly 18 months ago, when 12 speed Dura-Ace cranks were vaporware. I think it should be fine.

User avatar
Kurt1980
Posts: 339
Joined: Mon Oct 26, 2020 9:41 am

by Kurt1980

frnchy wrote:
Mon May 27, 2024 1:27 pm
Kurt1980 wrote:
Sun May 26, 2024 3:50 pm
Chasing this up as I also am looking to upgrade. My question is about chainrings specifically... will my existing 11 speed GRX chainrings work with an otherwise completely 12 speed GRX groupset?
Cheers.
Edit: It seems as though 12 speed chains still retain the 2.18mm internal width, but wondering if anyone has real world experience they can draw on.
Not GRX, but my 105 11 speed rings worked perfectly with a Shimano 12 speed chain. 11 speed chainrings + 12 speed chain was also popular with the pros roughly 18 months ago, when 12 speed Dura-Ace cranks were vaporware. I think it should be fine.
Thanks! I was thinking that's the case but good to hear it worked for at least n=1.

harblhat
Posts: 203
Joined: Mon Jul 18, 2011 12:18 am

by harblhat

The 12s front chainrings are closer together than 11s so shifting may not be as crisp. Once you adjust the high limit though to push it out a bit you should be fine.

trackflack
Posts: 49
Joined: Thu Jul 20, 2023 11:16 pm

by trackflack

My 11 speed chainrings are maybe not quite as quick with the 12 speed mech, but still work very well

satanas
Posts: 368
Joined: Sat Jul 04, 2020 5:45 pm

by satanas

IIRC from the EVs only the outer ring has changed, so if it really is closer you could just shim the 11 speed one inboard a tad.

SpeedyChix
Posts: 138
Joined: Fri Jul 28, 2006 1:34 pm
Location: Midwest USA

by SpeedyChix

How are 11-speed chains with the 12=speed drivetrain?
adrenaline junkie

harblhat
Posts: 203
Joined: Mon Jul 18, 2011 12:18 am

by harblhat

SpeedyChix wrote:
Sat Jun 22, 2024 2:07 am
How are 11-speed chains with the 12=speed drivetrain?
Bad idea. The 11s chains are wider and will mess with the tighter cassette cog spacing. The opposite is ok (12s chain with 11s drivetrain).

SpeedyChix
Posts: 138
Joined: Fri Jul 28, 2006 1:34 pm
Location: Midwest USA

by SpeedyChix

harblhat wrote:
Sat Jun 22, 2024 5:41 pm
SpeedyChix wrote:
Sat Jun 22, 2024 2:07 am
How are 11-speed chains with the 12=speed drivetrain?
Bad idea. The 11s chains are wider and will mess with the tighter cassette cog spacing. The opposite is ok (12s chain with 11s drivetrain).
Thanks for confirming.
adrenaline junkie

by Weenie


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