Shimano GRX RD 810 on 11-46t cassette, is it possible?
04-06-22, 08:03 AM
#26
Full Member
I run a GRX 600 2x crank in the front with a GRX-RD812 and an 11-42t in the rear. I swapped the stock cage for a mountain M8000 long cage. Can run big-big, small-small, and everything in between with no issues. Could probably put a 46t cassette for a 46-46 ratio but the 46-42 is already low. Works great, 1k+ miles later. Cage swap was $20.No reason it wouldn't work on a RD810 as well.
The RC 810 already has a long cage for 2 x 11 so it would not need the M6000 long cage. However, the parallelogram linkage moves at a shallower angle on the 810 than the 812 in order to stay close the the smaller 11-36 cassette gears, so you need to crank in the b screw and/or install a goat link to clear the low gears of a larger cassette. This moves the guide pulley farther away from the smaller diameter high gears affecting shifting at the high end, Without riding both to compare I can't say how noticeable the difference is but the long cage 812 should be better with the guide pulley remaining at a more constant distance from the cassette.
Last edited by bikeaddiction1; 04-06-22 at 09:58 AM. Reason: typo
04-06-22, 02:48 PM
#27
Member
Thanks for letting me know of your success. It gives more confidence in that mine will work well. Did you have to lengthen your chain? Mine is already at 116 links but looks like I will be able to use it.
The RC 810 already has a long cage for 2 x 11 so it would not need the M6000 long cage. However, the parallelogram linkage moves at a shallower angle on the 810 than the 812 in order to stay close the the smaller 11-36 cassette gears, so you need to crank in the b screw and/or install a goat link to clear the low gears of a larger cassette. This moves the guide pulley farther away from the smaller diameter high gears affecting shifting at the high end, Without riding both to compare I can't say how noticeable the difference is but the long cage 812 should be better with the guide pulley remaining at a more constant distance from the cassette.
The RC 810 already has a long cage for 2 x 11 so it would not need the M6000 long cage. However, the parallelogram linkage moves at a shallower angle on the 810 than the 812 in order to stay close the the smaller 11-36 cassette gears, so you need to crank in the b screw and/or install a goat link to clear the low gears of a larger cassette. This moves the guide pulley farther away from the smaller diameter high gears affecting shifting at the high end, Without riding both to compare I can't say how noticeable the difference is but the long cage 812 should be better with the guide pulley remaining at a more constant distance from the cassette.
Last edited by sdimattia; 04-06-22 at 03:00 PM.
04-06-22, 04:06 PM
#28
Senior Member
I have a 2 x 11 GRX 810 drivetrain with a 46/30 crank on my Salas Cutthroat. I have bought a GRX 812 rear derailleur and plan to do this:
As I already have an 11-42 cassette in the garage I don't plan to go to 11-46 unless I really feel I need the climbing gear when packs are loaded. If the XT SGS cages don't show up on time (I am told May or June) I may just pull the long cages off of the GRX 810 derailleur and put them on the 812, which I have read of others doing. Not only does the video show it working, but I have read accounts of others successfully doing this. I know there are cheaper solutions but IMHO making a derailleur that has the right climb angle for the 11-42 cassette and SGS cage for 2X crank should shift better than adding a Goat Link.
As I already have an 11-42 cassette in the garage I don't plan to go to 11-46 unless I really feel I need the climbing gear when packs are loaded. If the XT SGS cages don't show up on time (I am told May or June) I may just pull the long cages off of the GRX 810 derailleur and put them on the 812, which I have read of others doing. Not only does the video show it working, but I have read accounts of others successfully doing this. I know there are cheaper solutions but IMHO making a derailleur that has the right climb angle for the 11-42 cassette and SGS cage for 2X crank should shift better than adding a Goat Link.
Maybe worth a try instead of swapping cages.
04-06-22, 06:44 PM
#29
Full Member
I've covered a 11-42 range with a 48/32 up front with an unmodified Ultegra RX800 GS derailleur before. This derailleur has the same max sprocket 34T as your GRX 810. The B screw was almost all the in. I do remember the larger sprockets being a stiffer to shift into at the shifter, but otherwise it worked. I never used the easier gears so I dropped to 11-36T.
Maybe worth a try instead of swapping cages.
Maybe worth a try instead of swapping cages.
04-13-22, 11:56 AM
#30
Junior Member
For what its worth, I have a 105 R700 rear mech with an 11-40 XT cassette in the rear w/ a 50/34 chain ring setup in the front. B screw is in all the way, and it works fine without any derailleur hanger extenders or anything.
The only gear that doesn't quite work is when I am in the 34 chain ring up front and the 11 tooth cog in the rear (which I would never really do ever) - My chain is an uncut chain - all of the links are there. Will upload a pic soon. My point is, Shimano is conservative in this regard. I think my R7000 rear mech is rated for a max 34 tooth cog in the rear... and I'm running 40 with no problem w/ a 50/34 up front.
The only gear that doesn't quite work is when I am in the 34 chain ring up front and the 11 tooth cog in the rear (which I would never really do ever) - My chain is an uncut chain - all of the links are there. Will upload a pic soon. My point is, Shimano is conservative in this regard. I think my R7000 rear mech is rated for a max 34 tooth cog in the rear... and I'm running 40 with no problem w/ a 50/34 up front.
Last edited by 996; 04-13-22 at 12:00 PM.
