Drivetrain 1x12 or 2x10 for my MTB use case?

Question

I didn't ride bikes for quite some time and decided to start again this year. I'm currently looking for a MTB that will be kind of universal, I'm pretty much set on everything and picked few models, but now I'm faced with one final choice: either a model with 1x12 (Shimano Deore M6100) drivetrain or 2x10 (Shimano Deore M4120 and M618).

I'm going to use this bike on:

• forest trails

• gravel and dirt paths

• partially paved roads to get to actual trail I'm going to ride on

• lots of climbs and descents, not flat routes

I'm not going to use it to cycle in the city and (at least currently) I'm not even thinking about using it on more technical advanced trails. A friend told me that 1x11 or even 1x12 should be great for me, but when I was looking at the bike in the shop the dealer told me that for my use case 2x10 would be much better as it's more universal but not as great for highly technicals trails (that I don't know if I will even use).

Does it really make that much of a difference?

Answer 1

For your use case of 'universal' (many would call this oldschool XC) riding you want the widest gear range possible to allow pedalling up both steep climbs, but also on non technical downhills. At the same time, you want to preserve as small as possible gaps between gears to allow you to maintain a comfortable cadence.

For this use case a 2x10 setup is still clearly the best choice as it offers the same range as the most modern 1x setups with smaller jumps between gears.

Unfortunately the bike industry doesn't like to acknowledge this type of riding exists and is heavily pushing towards making 1x the only option for MTB. This is a shame, because a 2x12 MTB groupset would be extremely versatile and could be great for gravel bikes and even entry level road bikes.

Answer 2

Assuming that the recommended cassettes/chainrings are proposed, ranges will be equivalent.

• 36/26 chainrings, 11/42 cassette for the 2x10: 523%
• 10/51 for the 1x12: 510% (for 1x, the range of doesn't depend on the chainrings). Note that sometimes, 11/51 are offered with the M6100, so in that case the range advantage goes to the 2x.

There are also a lot of "redundant speeds" on a 2x10 setup, the number of actual different ratio is closer to 14 than 20.

But the range is just a ratio between the highest and lowest combination. It doesn't give any absolute indication.

So the answer will depend on the chainring: if the 1x12 has a 32T chainring, the range will be meant for lower speeds/steeper climbs. If the chainring has a 36T chainring, the two bikes will be really equivalents — replacing the chainring is usually simple, that being said.

Personally, just based on this difference, I would go for the 1x12. Simpler to operate, and also uses a slightly higher product range than the 2x10 and it's a more up to date design. The 1x12 also has a very small advantage if you want to fit larger tires.

Finding spares or upgrades will be easier: the 1x12 has just been upgraded on the whole Shimano mid- and upper- range (Deore M6100/SLX/XT), and you can mix components: you can have a XT shifter, SLX cassette and Deore derailleur. The 2x10 is a mid-range product, and the availability/offer of spares is already declining. From my research, finding spare cassettes for the M4120 is currently very complicated (hint: 2 of the 4 bikes at home use a 11/42 10-sp cassette), availability in Europe for this cassette is close to zero. What will happen in the future is only speculation, but seeing how the bike industry has reacted to the shortages, it was clear that the priority has been given to higher range products. So buying this specific configuration now is a bit of a bet:

• supply issues are solved, and in that case finding cassette won't be complicated. But the offer will probably limited to the steel ones — not an issue per se.
• supply issues are not solved, and in that case, you'll have the choice of running your bike with out of spec components or replace more just than the cassette because of a lack of spares (there's some nuance to that, but it's better to address it in a separate question).

[EDIT] I remembered that the RD-M4120 is actually a 10 AND 11 speed rear derailleur. Given 11/42 11-speed cassettes are still widespread (still the default for Shimano 1x gravel drivetrains and SRAM Apex). The argument of not finding spares is actually not valid for this rear derailleur. To use a 11 speed cassette, only the shifter (and the chain) needs be replaced, the rest can be kept as it is.

Answer 3

Not covered and answers already is durability and cost. A 12 speed drive train costs a lot more than a 10 speed, so when if comes time to replace worn (and broken) components, a 10 speed setup will cost you a lot less. However, 1x and and 11 and 12 speeds are superseding 10 speed. I may not be long before you cannot get easily quality 10 speed gear (similar to 26" tire these days - you can get them, but the range is limited and often need special order). Special order is OK for replacing parts that wear, but can be a pain with breakages.

The main reason the manufactures are in love with 12 speed is it frees the area around the bottom bracket of full suspension bikes. This is a highly stressed and crowded location on the frame, and removing the front derailleur allows a lot more freedom for designers. It also reduces assembly time but removing a complete set of shifters and derailleur, a big cost saving. If the frame can accept a front derailleur, you are not getting most of the benefit going to 1x gives manufacturers.

To me the decision is not about the technical aspects, as for your use case both drive trains will perform equally well. Its about what is more important to you - cost (immediate and ongoing) or sex appeal.

Answer 4

Personally, i ride a 3*10 setup on my MTB/Tourer. I think that this is a very good universal setup. Mine is set up so that most of the time i'm riding on the middle chainring, with a cadence of 85 - 90, which i am most comfortable with. The large and small chainrings are only needed for extreme situations, i.e. steep up- or downhill.

A high(ish) cadence is what you should aim for. It allows you to ride for a long time without too much effort. And to maintain your preferred cadence, you will want a fine spaced setup.

So i'd definitely vote for the 210, or a 310 setup for what you describe as your needs.