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What Shimano GRX rear derailleur should I be buying for a 1x application with small cassettes for CX type riding (11-32 to 11-36 max)? I seem to find different answers online everywhere I look…
2x rear derailleurs appear to be within (or close) to the capabilities of the cassettes I want to use:
GRX RD-RX400 (10 speed) min 11-32 max 11-36
GRX RD-RX810 (11 speed) min 11-30, max 11-34
GRX RD-RX820 (12 speed) min 11-34, max 11-36
1x specific rear derailleurs appear to be outside the capabilities of the cassettes I want to use:
No GRX 10 speed 1x rear derailleur?.
GRX RD-RX812 (11-speed) min 11-40, max 11-42
GRX RD-RX822-GS (12- speed) min/max 10-45
I guess the same question also applies to the 11-speed Di2 GRX rear derailleurs RD-RX815 and RD-RX817.
Any thoughts please?
I'd have thought the 2x version. Argument being that in a 2x setup you can normally use any rear gear with the chain on either front ring. That would suggest enough capacity.
I built my CX bike with 11-42t so went long cage. After one season questioning that choice now and the long cage looks less than ideal for a smaller cassette.
1x for a small cassette I reckon- I suspect the smallest large sprocket of 40t can be ignored but hopefully someone can confirm.
There are also widgets to get MTB mechs working so opening up Zee/XT medium cage etc potentially
Tanpans or similar at the back quite exposed for CX mud levels. Be interesting if there was a adapter that could be fitted in a more protected location.
Don't see why you can't ignore the smallest large sprocket restrictions. The bigger cassettes have 36t an they work fine. Yes there might be a bit more chain than you really need but that won't stop it working.
They will all work. A derailleur that can do 42 teeth also shifts 17-19 every ride no problems.
In theory the lower capacity one will shift better as it will sit closer to the cassette. It also less likely to catch on something.
You also have the choice of any modern road 10 or 11 speed derailleur. Some of these even have clutches.
Yes a narrow wide chain ring up front would be a good idea
Basically this:
You also have the choice of any modern road 10 or 11 speed derailleur. Some of these even have clutches.
IMO/IME shifting is a wee bit better without a clutch, and chain retention isn't that much of an issue once you have N/W rings, in which case why not just go for Ultegra?
All the GRX mechs have clutches which can be turned off. GRX 10/11/12 derailleurs have the same actuation as road 11/12 speed. To use a 10 speed cassette only Tiagra 4700 & GRX 10 speed shifters are compatible and you can use any of the GRX derailleurs. You can use any 11/12 speed road or GRX shifter with any of the GRX derailleurs matched to the appropriate cassette.
If you want to only use 11-34/36 cassette any of the 2x GRX derailleurs is fine with the caveat that possibly the pulley/guide wheels are optimised for 10/11/12 speed chains depending which derailleur you choose. The 810 & 820 have bearings instead of bushing in the RX400. I am currently using a Deore M6000 mech (42t min/max largest sprocket) with a 11-36 cassette and it shifts fine.
Good little video about clutches and narrow/wide rings