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 letās just say very creative with the B Screw. I wouldnāt make it a daily driver. 31-45 was very welcome up Lookout ridge in lastyearās Sea Otter Gravel race.
Right, it can āworkā 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 canāt just grab 3 gears and hammer. Itās 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. Thereās 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 āsmoothā. I described it at the time as shifting like a lower tier groupset.
I hadnāt 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 itās the parallelogram that determines cassette range but the length of pulley cage that determines whether thereās 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)
Iāve 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 donāt 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.
Iām 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 ?