Compatible derailleur/hanger and going 1x

Question

So the green Kona dew plus is my bike. It's an 8-speed with a 11-34 cassette. It came factory with an Alivio 9-speed derailleur. I need to upgrade the rear derailleur because I got hit by a taxi. My options are slim for 8/9-speed compatible derailleurs. Basically, the Deore RD-M591 and RD-M592. Anything else?

Which would you prefer, the Deore RD-M591 or RD-M592

Second question: What are my options if I wanted to upgrade to 1x and keep my current hub. As I understand it, I can use the Shimano Deore 11s M5100 groupset, 1x11. What about the front chainring? Can I still use my current crank? What front chainring should I get? Do I have other options? How about the Ultegra r8000 derailleur and the road bike flat bar style shifters. Is there a cassette compatible with my hub? Does that even make sense? If I upgrade my hub what better options are there?

Answer 1

The term "direct mount" has been used to mean a few different things with rear derailleurs, and it can cause confusion.

By Shimano's definition, your frame does not have a direct mount. You have the far more common "direct attachment," which most people would just view as a normal, non-weird hanger. Shimano Direct Mount is a different standard for derailleur hanger position relative to the axle. Onto it you install a derailleur such as your Alivio, but you don't use the b-link. In other words, the position of the mounting hole relative to the axle on a Shimano Direct Mount compatible hanger is the same as what the b-link also provides. Notice how in the image, the RDs pictured are the same except for the absence of the b-link on the right.

If you just wanted to upgrade the RD without altering the drivetrain setup much, yes just get RD-M592. It's a very good part and is basically just an improved version of what you had. M591 would also do the job, as would another of the same Alivio. M591 is not a Shadow derailleur; personally I think Shadow is a good thing because it helps prevent damage, but it's not a critical difference.

If you were going to 1x the bike, your hub is only a limiting factor insofar as it prevents you from running any of the 10t cassettes. So, for example, a mid-price approach would be RD-M5100, an 11-speed shifter for it, an 11-51 11-speed cassette, chain, and switching the middle ring to a narrow-wide with whatever tooth count you decide is right for your gearing needs. The chainline would likely work with the current BB, but you should also be prepared to fiddle with it. Overall it's typically not worth it, although there can be exceptions to that if lots of things are worn out or broken and you intend to keep the bike either way. The road 1x groups don't really offer anything different functionally on a flatbar bike, unless you wanted narrower gearing range. The first question when contemplating a switch to 1x is what your gearing needs are.

Answer 2

To complete Nathan's answer, a few points:

• going to 1x also requires a change of chainring: you need a chainring with a narrow-wide pattern (those are designed to keep the chain, while the current ones are designed to "derail"), and possibly a chainguard. It's usually possible to buy the chainring separately from the crank.
• road groupsets are usually not designed to be used in 1x configuration and lack the clutch. The ones that can be used are high range ones, and have little added value compared to the mid range MTB ones. Gravel groupsets are also designed to be used in 1x, but again, no added value compared to their MTB equivalents.
• on top of the M5100, you also have the M5130 Linkglide among the options. It's only 10-speed 11-43, but has a different tooth profile that is in theory more durable. There's also the Advent (9-speed) or Advent X (10-speed) ranges of Microshift.

About the relevancy of upgrading to 1x: if you have to replace the hub and rear derailleur and can keep your current cranks, why not, if you are sure to have all the range with mid-range components (Deore 51x0 or Advent (X)). The extra cost is then limited (shifter and chainring). Compared to the value of the bike, it can be a lot, but the absolute amount remains reasonable. On the technical relevancy, it depends how you use the bike. The only case where I think the 2x/3x have an advantage over 1x is the ability to shift one chainring down when you need to stop suddenly - common in urban riding (in term of effect, you could achieve the same by shifting 3 speeds up rear, that can be done in one stroke, but it is much slower). One advantage I see is not so much in the 1x vs 3x question, but in Deore vs Acera/Alivio: the difference in shifting performance is noticeable - especially on the long run. Just upgrading the rear derailleur (M592) won't give you the same effect, as the shifter matters as well, and you can't find mid-range 9 speed shifters nowadays.