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Is it possible to have a 3x9 setup - Triple 42T ( 42-32-24 ) x 9s ( 11-13-16-20-24-28-32-36-42T )? The main question is, what kind of 9 speed derailleur is compatible and how long chain need to be for this kind of setup? Thank you

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  • 1
    What are the tooth counts on your chainrings ?
    – Criggie
    Dec 14, 2022 at 19:54
  • The 50T capacity of your rear derailleur; is that the maximum range of chain allowed (from most taught to most slack) OR is 50T the largest cassette cog diameter it can handle? Listing it as 50T makes me think T = Tooth cog. Bit if it is chain length capacity it would be 50 links, not teeth.
    – Ted Hohl
    Dec 14, 2022 at 19:59
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    Yes that is Max capacity of 9 speed LC derailleur ( 50T ), I found only one model L Twoo A5 Elite 9s LC
    – Chechi'son
    Dec 14, 2022 at 20:59
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    Anecdotally, I ran a similar setup, 3x11, on a 26" touring bike (Surly Troll). A Shimano FC-M8000-3 (40-30-22 chainrings), a CS-M8000 (11-42t), and a RD-M8000-SGS (capacity 47t). As long as you don't cross-chain it works fine, even though you are outside Shimano's specs. A 126-link chain was long enough, and it's perfectly possible to ride up steep hills in the 22-42 without falling over.
    – Tristan C.
    Dec 15, 2022 at 7:24
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    what part of the this setup is weird?
    – njzk2
    Dec 15, 2022 at 21:42

2 Answers 2

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If you had 42-32-22 in front and 11-42 in back, the derailleur would need 51t of capacity. A bit of casual searching revealed that the highest wrap capacity I could find on a newish derailleur is 47t, which would limit you to a 37t big sprocket in back.

Chain length isn't really a problem--you can find chains long enough for your purposes.

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  • Yes i have that setup specs to put on a bike.. 3x ( 42-32-22 ) for the front and 9 speed ( 11-42T ) for the back, the derailleur I found, only one that is meeting criteria but there is a catch, it is short for a teeth, it is Chinese derailleur: L Twoo A5 Long Cage Elite max 50T. So will it work?
    – Chechi'son
    Dec 14, 2022 at 20:36
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    Shimano are reasonably conservative with specs; you may find that exceeding the capacity will work well enough for you, especially if you never cross chain.
    – mattnz
    Dec 14, 2022 at 20:50
  • I can find chains long enough for a recumbent, basically, you can find bike shops that have 'endless' chains.
    – Willeke
    Dec 14, 2022 at 21:20
  • I was checking something and I was wrong, it is not 22, the right number of teeth for the front crank is 42-32-24
    – Chechi'son
    Dec 15, 2022 at 2:43
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    One could also just avoid using the 22 / 11 combination, it is redundant with the 32 / 15 ratio available with middle chainring.
    – jpa
    Dec 15, 2022 at 14:23
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22:42 gearing is a ratio of 0.52 or 13.6 gear-inches on 26" wheels. That will be around 5 km/h or 3 mph in bottom gear at 90 RPM on the crank. You may not be able to balance at such slow speeds and high cadences.
Source https://www.sheldonbrown.com/gear-calc.html

Are you handy with tools? If you're capable of modifying a rear derailleur and fabricating a longer cage that may be one way to give more capacity. Downside is the chain gets closer to the ground and will get dirtier, and risks striking rocks more.

As for chain length - if one's not enough you'll need two packs of identical chain and join them. I find it better to buy three, so I have enough chain for the next replacement without having to source one more identical chain - this helps with tolerances.

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  • 3x ( 42-32-22 ) for the front and 9 speed ( 11-42T ) for the back, the derailleur I found is L Twoo 9speed A5 Long Cage with max 50T so the question is, will it work..
    – Chechi'son
    Dec 14, 2022 at 20:43
  • In theory, I decided to try this Frankestein configuration, because I have all the parts except the compatabile derilleur. When I go up my favorite hill, it's always at an angle of 115, 120 + degrees and almost every time I die when i reach near the top, and again I want to be able to descend, in peace drive downhill through easy to medium trails ... and maybe more importantly, maintain a relatively high speed in continuity up to 50 km on 26x1.95 tires..
    – Chechi'son
    Dec 14, 2022 at 20:52
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    @Chechi'son 115 degree climb would be an overhang. The maximum percentage for a paved public road anywhere in the world is Baldwin Street at about 1:2.86 (19° or 35%) Off road trails will be steeper, but you're not riding up a vertical wall. Can you post a strava segment link ?
    – Criggie
    Dec 14, 2022 at 21:13
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    With a 26" or bigger wheel the derailleur case should not be a problem. (I have had a long cage on a 20" recumbent and it did hit the ground on normal roads.)
    – Willeke
    Dec 14, 2022 at 21:22
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    lowest gear I used for any amount of time was 22:28 (I might have used the 22:32 for short bits on that same section), and that's already not super stable
    – njzk2
    Dec 15, 2022 at 21:48

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