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I have a 1x9 that I really dislike and want to upgrade. I was told to get a "Shimano Deore FC-M625 Double 2x10 Speed MTB Bike Crankset 38/24T" to upgrade my 1x. I additionally caught a branch on a downed log and twisted my rear derailleur, so I bought new Shimano Alivio RD-MD3100-SGS due to the Acera being out of stock.

The specs say 36T max low sprocket, but I wondered if I added the Wolftooth Goatlink could I upgrade to a 11x42T cassette?

I see the total capacity states 45T, so if I calculate correctly the 38-24=14 and the 42-11=31 (14+31=45) then I should max out at the 45T capacity. Am I on track with the increased cassette with this derailleur and the addition of the 2x crankset?

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    Hacks such as the Goat link belong to the past when wide range gears sets were very expensive. Have a look at microShift Advent if you want a cost effective 11-42 1x that works.
    – mattnz
    Jun 15 at 21:59
  • Keep in mind that a 9 speed setup with 11–42 cassette has very wide gear steps. Around ~20% for each step. I think a single chainring crankset with a 11–42 cassette (or similar) really only makes sense with at least 11 speeds in the rear.
    – Michael
    Jun 16 at 9:02
  • I am going to move to a 2x crankset, I do not like the 1X and maybe your comment of needing an 11 speed makes more sense of why I do not like the 1x9. I am looking to add a 38/24t crankset as soon I can get my hands on it, of course as you know components are not easily obtained right now. Jun 16 at 13:07
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    @AndyP On a (presumably) MTB, 36/11 at 100rpm on a 29er is 45km/h. That’s plenty, unless you’re riding faster than that.
    – MaplePanda
    Jun 19 at 7:11
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    @Michael Depends on local terrain. If you have roadie or XC-style rolling terrain that requires smooth cadence shifts, that won’t work well. However, if you’re riding gravel road up, pure descent down type terrain, you really only need the bottom 2-3 and top 2-3 gears. The middle are just filler.
    – MaplePanda
    Jun 19 at 7:13
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I'm currently running a RD-M3000 (which seem to match the specs of the RD-M3100) with a 11-42 cassette 9-speed (Advent). The original cassette was a 11/36.

So a few comments about this experience:

  • no goatlink necessary
  • to make it work, you have to adjust the B-screw, which means putting the derailleur cage further away from the cassette. Gear changes are less direct than before, especially on the small cogs (they were not specially direct before, that being said, it's the kind of things where you see a difference between Deore and Acera/Alivio).
  • the design of the cage of the RD-M3000 is not ideal for that kind of use (it can have changed with the RD-M3100 though): the inside plate of the cage goes "above" the jockey wheel — this part usually finishes near the axle of the jockey wheel. It causes a problem for me in the combination big chainring/big sprocket: the cage get blocked by the sprocket, so I have to shift to the small chainring to escape this situation. It could be avoided by adjusting the b-screw, but the shifts will be less responsive. This problem may not happen if the gap between the chainrings is smaller than 16 teeth, that being said.

About your idea of going 2x, since it would imply to replace the drive train, a few comments to:

  • make sure that you can pass a cable for the front derailleur and that your frame can accommodate a front derailleur (it's not always the case, especially with hydroformed tubes)
  • the crankset that you mention is a 10-speed one. 9-speed chains are wider than 10-speed chains, so that might not be optimum
  • Going 9-speed with an 11/42 cassette is going quite exotic (basically only Microshift if you want to stay as close as possible of the specs, but Microshift claims that Advent derailleurs require Advent shifters, so it adds another supply hurdle). If your constraint is more supply than budget, going to something more "mainstream" might be easier for you: for instance something like M5100 (11 speed, 1x11/51) or Shimano M4100 (2x10) might offer you more possibilities in term of supply without being too expensive.
  • deriving from the comments: going 2x to have more "intermediate" steps is not necessary a good approach for me: if you think you miss a ratio between 2 cogs, and this speed is ratio is present using the other chainring, it will require you to know which combination it is and switch chainring and sprockets, which is never done in practice.
  • check the clearance between the chain and the wheel, if you have large tires and not a boost axle: with a 2x, the chain will be a bit closer to the tire, better to make sure you can safely do it.
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  • “deriving from the comments: going 2x to have more "intermediate" steps is not necessary a good approach for me” The thing is that with a 2x setup you can go for a normal 11–34 cassette which has much smaller steps than a 11–42 cassette.
    – Michael
    Jun 18 at 12:38
  • It's right, but I would add that it depends also on the distribution of the sprockets. If I compare my previous 11/36 with the current 11/46, the difference is mostly noticeable in the largest sprockets, and less in the smaller ones — where differences are more noticeable (11-13-15-17-20-23-26-30-36 vs 11-13-15-18-21-24-28-34-42).
    – Renaud
    Jun 18 at 12:49
  • Renaud, lots of good information to add to my learning curve of gearing. I believe at this point I have read elsewhere and you also commented that 11/42 cassette will work with this derailleur, without the goatlink. As far as the crankset, I did visit a bike shop and that was the recommended crankset by them. I am liking this thread and communication, because once I started researching I wondered if this was his preference and after @AndyP suggested a 36/22 crankset, I see where that gets me closer to what I feel the ratio I am looking for. I am riding a 27.5" wheel DiamondBack Line. Jun 25 at 20:15
  • @Renaud the front derailleur I was told by the local bike shop is a clamp band and designed for larger frames. SHIMANO ALIVIO SIDE SWING Front Derailleur (Clamp Band) 2x9-speed model FD-M3120-M-B Jun 25 at 20:24
  • @JacobArmstrong Actually someone posted a picture of a RD-M3000 here bicycles.stackexchange.com/questions/77488/… and the one depicted in the picture doesn't have the same cage as mine and wouldn't have the problem mentioned in my third bullet.
    – Renaud
    Jun 25 at 20:24

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