Eight years ago, SRAM released the first 1X specific
drivetrain. I remember Nino Schurter winning on it
within weeks of it being shown to the public,
which was an early sign that 1X was going to pave the way for drivetrains to
come. Fast forward to 2020, and 1X
drivetrains feature on a large percentage of bikes.
According to my Bikepacking Bike Buyer's Guide, it's two-thirds
of all 27.5-inch gravel bikes and close to 100%
of mountain bikes. So, are one by systems the ultimate drivetrain
or is there still a place for 2X and 3X?
Today, we are going to analyze every aspect of bicycle drivetrains.
We will be looking at all data available across eight different categories to
find out, once and for all, which drivetrain is best. Number 1:
Drive Resistance. VeloNews has lab tested the resistance for both 1X and
2X drivetrains, and the conclusion is clear:
2X is the most efficient across all gears. The main reason for the higher
resistance is greater chain angles from the
chainring to the cassette, which results in the chainplates
scraping harder on the cogs. But additionally, when you use the smaller
chainrings and cogs found on a 1X system, the chain tension is higher,
the chain speed (or tooth-interactions-per-minute)
is faster, and a chain has to articulate more to wrap around the smaller cogs.
The result is about 2 watts less drivetrain efficiency on average,
but it's 4 to 6 watts in the three highest gears.
That said, there is also data available suggesting that SRAM chains run slower
than Shimano chains, so the number might be a touch less.
Number 2: Gear Steps. Cadence is the number of times your crank spin per
minute when you ride, and just like your car engine, you'll
have an ideal RPM range where you can pedal efficiently.
My preference is to pedal along at somewhere between 80
and 90 RPM. In an ideal world, our cadence would remain constant as we increase in
speed, but this is not possible on a bike with gears. The next best thing
is to make the difference between gear changes as small as possible so you can
stay in your optimal RPM range for longer. We
can do this by minimizing the gear steps between each cog
on a cassette. Most cassettes used for touring and bikepacking have
13% to 15% gear steps. You'll notice there isn't a huge difference between 11-36T
and 11-42T cassettes because the latter offers an extra gear to account for the
42 tooth cog. But gear steps are pretty abstract, so I
prefer to graph them using cadence differences. These graphs
show the specific range of speeds for each gear between two selected
RPMs. A crossover in the graph signifies a smaller cadence difference than those
selected, while any gap in the graph results in a
bigger cadence difference. At my typical cadence, an upshift on a
1x12 drivetrain will slow my cadence by 13 RPM.
Comparatively, my cadence will slow by 11 RPM
using a 2x11 or 3x10 drivetrain, allowing me
to stay between 80 and 90 RPM for longer.
Number 3: Gear Range. Your bike's gear range, which is measured as a percentage,
determines the speeds at which you can pedal your bike. It was not that long ago
when one by drivetrains were limited to 420%,
but these days, there is much less of a difference in gear range between all
drivetrains. A great way to visualize gear range is
to peg the lowest gear at a set speed for all drivetrains,
and then calculate what the top speed will be. In this example,
the 1X bikes top out at 47 to 48 kilometres per hour
in their highest gear, while a 2X or 3X bike will offer 15 to 20%
more speed, topping out at 56 to 57 kilometres per
hour.
Number 4: Availability and Compatibility.
As I specialize in bike travel, parts availability and compatibility
are two important aspects of any drivetrain for me. Speaking of which,
if you want to learn everything about bikes, definitely check out the Bikepacking
Bike Buyer's Guide or Touring Bicycle Buyer's Guide, which are linked in
the description. Available spare parts usually go hand in
hand with the bikes that shop sell. You can find $800 mountain bikes in the
capital cities of most countries, which are now specced with 10-speed
drivetrains, and bikes that are not much more expensive come with 11 speed
components too. In comparison, 12 speed parts are harder to come by
in low-income countries, but I suspect that won't be for long.
While 8, 9, 10 and 11-speed drivetrain users can mix and match between brands
without much concern, 12-speed SRAM uses oversized chain
rollers to mate with their cassettes, and 12-speed Shimano only really works
well with Shimano. Number 5: Chain Longevity. There is a
misconception that newer, narrower chains often found on 1X
drivetrains are not as durable as older chains. Zero
Friction Cycling has done a lot of testing in this space
and has found that 12-speed chains are actually the most durable chains ever
created. And not by a small margin either. More
than 30 chains have been tested by Adam on a converted smart trainer,
with lubrication and contamination
controlled. The test is stopped
when the chain reaches 0.5% wear, as
this is the point where the chain starts to accelerate the wear on your cassette
and chainrings. High-quality, 12-speed chains are lasting
4000-7000 kilometres in this test,
with equivalent 11-speed chains running closer to 3000 kilometres,
and even less longevity for chains with fewer speeds.
If these numbers look a little bit low, it's because the chains were tested with
contamination to simulate real-world conditions. You can reduce
chain wear by riding in dry environments, by keeping your chain super clean, or by
using a wax lubricant.
Number 6: Price. According to Zero Friction Cycling,
you should get three chains to one cassette, and as many as six chains to
your chainrings. By knowing when a chain will get to 0.5%
wear, we can estimate the long-term running
costs of different drivetrains. Assuming an environment with similar
conditions to those controlled for by Zero Friction Cycling,
the bikes with the front derailleurs should be the cheapest to run.
Number 7: Ease of Use. For a beginner, there is no doubt that a 1X
drivetrain is the easiest to use. If you want to go faster, you go up a
gear, and if you want to go slower - you go down. In comparison, using a 2X
or 3X drivetrain takes a little more practice.
To avoid cross-chaining, you'll want to use the biggest cassette cogs with the
smallest front chainrings, and the smallest cassette cogs with the
biggest front chainrings. Additionally, something that is easy to
use should also be easy to maintain. With fewer components, 1X is the
obvious winner here.
Number 8: Tyre Clearance and Shorter Chainstays.
The reason why 1X is so widely adopted on mountain bikes
often comes down to frame design. Both the front derailleur
and inner chainring chainline can interfere with the rear tyre,
restricting how short the chainstays of a bike can be.
Usually, shorter chainstays are preferred on mountain bikes as they make it easier
to lift the front wheel over obstacles, as well as making the bike feel more
playful to ride. Additionally, the pivot locations and
tube shapes on full suspension bikes can be limited by front derailleur
infrastructure, so that's why most full suspension bikes
are now exclusively 1X.
In this head-to-head, the 2X drivetrain took home five points,
the 3X system won four, and the 1X setup
ended up with three. But ultimately, you'll need to pick the drivetrain that
best suits the type of riding you do. The newest kid on the block, 1X, is
certainly more user-friendly, and the 12-speed chain durability
is incredible. For mountain bikers, 1X allows for frame designs with
fewer compromises, and if you spend a lot of your time on
steep terrain, the bigger gear steps will not be particularly noticeable.
However, the case is as strong as ever for front derailleurs, as they will
provide lower drivetrain resistance, a wider gear range, and a smaller cadence
difference between each shift. If you value my bike-nerd content,
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