Shimano GRX 810, Shadow RD+

I have a 2021 Topstone 1 with the GRX 810 Shadow RD+ and FSA Omega AGX+ 46/30 crank and GRX 800 front derailure.  Shimano claims the GRX 810 can only handle a 34t max cassette and 40t total.  Im wondering if anyone has tried a larger cassette with this setup?  Ideally I would like the 11-40 or 11-42 cassette painted with the 46/30 crank, 

The GRX 810 can handle a 11/40 cassette with 46/30 crankset without adaptator. I had personnaly test 47/32 crankset and 11/40 cassette on 2 days bikepacking without any problem.

You can go to 11/42 with wolftooth goatlink : https://www.youtube.com/watch?v=sRgLG1uP_uo

I have a Rotor 3D+ 50/34, XT 11-42 on a GRX RD-RX810 with no special setup needed. Goatlink/longer B screw not required.

I’ve installed a 11-42 with a GRX 48/31 crank and so far so good.  No special B screw or RoadLink however in the 42t the RD is close.

I have an 11-46 cassette and a 46/30 crank with my GRX setup. I did get a Wolf Tooth Roadlink DM and I replaced the lower jockey wheel with a 16 tooth to increase the capacity a bit. 

Shifting is a little slower but not bad. Every combination is usable. I think I could fit a larger cassette by adjusting the B screw but then I might have to give up on the big-big or small-small combinations.

jannmayer wrote:I have an 11-46 cassette and a 46/30 crank with my GRX setup. I did get a Wolf Tooth Roadlink DM and I replaced the lower jockey wheel with a 16 tooth to increase the capacity a bit.

Old but informative thread - having read this I bought a 14T jockey wheel and can confirm that is takes up quite a bit of slack vs the stock 11T pulley.  This extra capacity translates in my case to two more useable small cogs when in the small chainring.  Very useful.  Thanks @jannmayer for the tip.  For reference I am using a 46/30x11-40 setup with GRX400 derailleur.  16T would not have fit this particular cage.

jannmayer wrote:I have an 11-46 cassette and a 46/30 crank with my GRX setup. I did get a Wolf Tooth Roadlink DM and I replaced the lower jockey wheel with a 16 tooth to increase the capacity a bit. 

Shifting is a little slower but not bad. Every combination is usable. I think I could fit a larger cassette by adjusting the B screw but then I might have to give up on the big-big or small-small combinations.

. Just installed a Wolfy and a 11-46 with the 48/31 GRX cranks (all that was in stock) and the 810 RD seems to work good after one ride.  Can you help me understand the lower jockey wheel issue?  I understand larger wheel receives slack in the small small type gears but how did you decide on a 16 AND does it make shifting any better?  MTBNUT87 has given me great ideas as he is running 11-51!

Gasman wrote:. Just installed a Wolfy and a 11-46 with the 48/31 GRX cranks (all that was in stock) and the 810 RD seems to work good after one ride.  Can you help me understand the lower jockey wheel issue?  I understand larger wheel receives slack in the small small type gears but how did you decide on a 16 AND does it make shifting any better?  MTBNUT87 has given me great ideas as he is running 11-51!

I'm glad to head it works with the stock jockey wheel! I actually did not test it with the stock wheel. I read somewhere that switching to a larger jockey wheel effectively lengthens the derailleur cage and helps it account for the extreme difference in chain tension between the big-big and small-small combinations. I was concerned that I would not be able to shift safely into all combinations with the stock jockey wheel. It shouldn't actually have any effect on the smoothness of the shifting.

I decided on a 16T wheel because I guessed it was the biggest that would fit in the stock cage.

Thanks…here is what it looks like currently, I think you can tell from the RD, big-little, big-big, little-little and little-big.   It shifts buy not always perfect.  I had the b screw all the way in for the 11-42 cassette w no Wolftooth (but the 810 RD does have an extension) so Im still playing with the b screw and cable tension to adjust.  Would a larger pulley help shifting?  Im having a little trouble in the middle of the cassette actually.  No issues with the large cog.

I can't say for certain, but it is possible a larger jockey wheel should help increase chain tension when you are in the small chainring and on the smaller cogs. I wouldn't expect it to make much difference for other combinations though. However, you can find jockey wheels for pretty cheap, so it's an easy experiment.

I also has some difficulty getting the shifting dialed in at first. I replaced my derailleur hanger and it got much better. I suspect that a setup like this is more sensitive to derailleur hanger alignment issues. Some cassettes may also not shift as smoothly as Shimano and SRAM ones.

I also accept that the shifting won't be a smooth as a more conventional setup, but that is a worthwhile trade for me.

[QUOTE username=Gasman userid=7031623 postid=1334476425]Thanks…here is what it looks like currently, I think you can tell from the RD, big-little, big-big, little-little and little-big.   It shifts buy not always perfect.  I had the b screw all the way in for the 11-42 cassette w no Wolftooth (but the 810 RD does have an extension) so Im still playing with the b screw and cable tension to adjust.  Would a larger pulley help shifting?  Im having a little trouble in the middle of the cassette actually.  No issues with the large cog.]


[/QUOTE



It's possible you haven't relaxed the b-screw enough yet.  I think there may be more than the necessary clearance between the chain and large cog, so perhaps try to back it out more and see if this improves the shifting in the middle gears.  I suspect all a larger pulley will do is take up some of the slack when the cage is rearward, meaning small-small.  This has been helpful to me but does not in my case improve shifting.