This effectively allows you to run a 48/31 with an 11-40t cassette with no issues whatsoever. Including running it in a 48/40 setup (though I never would).
The 11-42t will not work(without some b-screw finesse) so please dont order it hoping it will shift idyllic.
Shimano lists the 817 as working with the 11-42. I got a 11-45 to work with this setup, but was letâs just say very creative with the B Screw. I wouldnât make it a daily driver. 31-45 was very welcome up Lookout ridge in lastyearâs Sea Otter Gravel race.
Right, it can âworkâ but the 11-40 requires nothing creative and shifts perfect. Have a buddy running a 1x with the Campagnolo 9-45 but you gotta be cognizant of that last shift lol. Like dont be hammering 300w and expecting a prototypical shift. However, the 817 with the 2x and 11-40 shifts pretty identical to the 815 with the 11-34.
Correct. You canât just grab 3 gears and hammer. Itâs more of a one cog at a time thing with the big bailout gear. Makes me think going mechanical 12 speed with a mullet cassette would be a better idea.
Maxing out the limit screw might not be the way to go. That causes it to no longer sit flush against the stop which over time will eat away at the stop. Thereâs a few vids on Youtube showing this issue.
Easiest way to get 11-40 to work with RX815 without issue is using a Goatlink 10 or 11. No other components needed. On the Goatlink the derailleur stop is angled further back meaning the derailleur screw will sit flush limiting excess forces.
Really interesting to see this! I used unmodified 2x11 RX810 mechanical derailleurs with 11-40 and 46/30 for an ultra last year and it was reliable but far from being âsmoothâ. I described it at the time as shifting like a lower tier groupset.
I hadnât thought about swapping pulley cages though, and I do have a spare RX812 rear mech from a bike that used to be 1x. Will the 810/815 cage fit an 812/817 mech or does it need to be an m8000 cage?
(And just in case my logic is off: my understanding is that itâs the parallelogram that determines cassette range but the length of pulley cage that determines whether thereâs enough total tooth capacity for a front mech, so the goal here is to use a 1x mech with a 2x cage to maximise both capacities at once)
Iâve been running the same set up but with a larger 16t guide pulley and an 11-42 cassette with no issues. Limit screw is not even maxed out. I donât think I would be hammering away and quickly pulling across the cassette, but I am quite confident with the shifting quality
Been running an 11-40 cassette from the day I bought the bike. No issue and it makes life much easier when the daily TSS is above 600 and you still have hills to climb.
Not sure on app integration, but it fires from the shifters exactly the same. I had it set before to jump up/down 1 cog on the rear when changing from big/small up front. After connecting the 817 it still does the same.
Iâm hoping to do this mod using a mechanical grx 812 derailleur and swapping the longer cage from my current grx 810 derailleur as opposed to buying the RD-m8000 pulley cages. Has anyone done that successfully ?
I have a similar question. I have the standard 11-2peed 2x GRX Di2 Front and Rear derailleurs. Iâve been running an 11-34 cassette with a Praxis 48-32 crankset and just put the Shimano 11-40 on my bike. I adjusted the b-limit screw and itâs shifting fine but is too close if I am in the 48-40 (I know this is to be avoided.) I did not add any links to the chain nor change it out. What else is recommended to ensure safe and smooth performance?
Should I keep adjusting the b-limit to allow clearance? Should I swap the chain? Is there any programming I can do in the Etube app to limit the large-large shifting? Thanks for any advice.
I had this on my previous bike, loved it. Youâll need to extend the b limit almost most of the way out, and yes youâll need to resize the chain. I had it so it would work fine in big-big and small-small.
In theory, could I slap a road crankset on? I like this, but feel like a 31, 40 is a bit too slow for my gravel. Could I do like a 52-36 with a 36- 40? That would be epic. Or heck, for a pedal everywhere road bike, could I do a 54-40? Basically, if the bike can clear the chainring, does the size matter?
