The trend is being set lately and an increasing number of riders are going to a 1x driveline system from the 3x and 2x of the past. With 10 speed cassettes being the norm in mountain biking these days, its easy to have a relatively wide range of gears with only one chainring. Is a 1x driveline right for you and your riding? Only you can answer that question.
The 3x driveline
The 3x 10/9/8 drivetrain has been the standard of mountain biking since the '80s. Offering a wide range of gear choices it is a truly versatile setup. Modern 3x drivelines usually consist of 24/32/42 chainrings paired with a 11-36 10 speed cassette.
-Widest range of gear choices possible
-Least chain and gear wear
-Best chain retention
-Heaviest setup of all the drivelines
-Most overlap (redundant) gears
The 2x Driveline
The 2x came to popularity when 10 speed cassettes became the norm. Offering almost all the gearing of the 3x and only losing the highest and lowest useable gears.
-All of the most used gears in an easier to use package
-Less redundant gears compared to 3x
-Less cross-chaining compared to 3x
-Still the same weight as a 3x system (save for one ring)
-Loss of your lowest stump pulling gears
-Loss of your top gears
The 1x Driveline
The simplest and lightest setup of the bunch, losing two rings, the front derailleur, and a shifter. It also comes with the most compromise in gear choices. Wider range gearing can be kept intact with cassette adaptors and chainrings for 104bcd now available with 30 teeth.
-Simplest of the bunch
-Best obstacle clearance
-Loses the most gears compared to 2x/3x drives
-Cassette adaptors can be expensive if you want a wider range
In my opinion, the 2x system has the most compromise without much in the way of gains. I do like the 22/32/bashring 2x combo on my fatbike though, but this setup keeps the low gears and loses the high ones compared to the more common 28/36 2x setups. For this reason I'm disregarding the 2x systems from here on out.
Lets take a look at some gear range setups between 3x and 1x
Above is a typical 3x10 driveline gear inch chart on the left with a 1x chart on the right comparing 30 / 32 / 34 tooth chainrings. As you can see, with the 30t chainring you basically don't lose any low gears but you take away your 3 highest gears compared to the 3x drive. I don't know any mountain bikers who use their top three all that often honestly. With the 32t you lose one gear off the bottom and two off the top compared to 3x. With 34t you almost lose two off the bottom and pretty much keep all but your highest gear. Now the advantage of the 1x system gets a little clearer, you are keeping nearly all of your gear range from your 3x system and can lose up to one pound off your bike by ditching the 3x components. Factor in having a few different size chainrings in your parts bin and you can change your gearing to suit each trail if needed. That said, the 3x system still has the advantage as far as tuning your cadence as there are more options to choose if you really work the gears, and not as large jumps between gears as the 1x. 3x also has an advantage over 1x for driveline wear. Larger gears wear out slower than smaller ones, so when you have a road section or some really fast trail you can pop into the 42t ring and 21 out back to keep from wearing a similar ratio of 32x15. Larger gears also have more chain retention and are less likely to skip of bounce off in hard terrain, although the current crop of "clutch" type rear derailleurs will keep your chain planted no matter what you run into.
Is 1x right for you? I'm sure most riders make do with less than 10 gears anyways but its what you are comfortable with. I'm running a 22/32/bash on my fat bike and really enjoy the 22-36 gear for spinning fast and going slow in deep snow. I'm also currently running a 24/32/42 3x on my 29er, but when that setup wears out I might opt for a 1x with a cassette adaptor as I don't really use my lowest gears on the 29er, or the highest for that matter.
Clear as mud?
The Bric...._ mountain biker, road rider, heavyweight gear abuser. Built like a brick sh*thouse. No bike is safe.