This post compares the advantages and disadvantages of 2×11 and 3×9 bicycle drivetrains.
The Advantages of 3×9
- Extreme Gear Range
3x drivetrains offer the greatest number of gears and the widest gear range.
The largest ring provides a lot of top speed whereas the smallest ring (a.k.a. granny ring) coupled with the largest cog will help you climb almost any hill.
When comparing gearing it’s necessary to become acquainted with the term gear ratio.
The gear ratio shows the number of rotations that the rear cog and respectively the rear wheel make per 1 full revolution of the cranks.
The gear ratio is derived from the number of teeth on the chainring and cog. For example, if the chainring has 42 teeth and the cog has 11, the gear ratio is 42:11= 3.8. In this, case the rear wheel makes 3.8 rotations for every revolution of cranks/chainring(s).
The higher the gear ratio, the greater the potential speed of the bike in that gear.
To find out the speed that a bicycle can reach via pedaling in a specific gear, one needs the following values:
- Gear Ratio
- RPM (rotations of the cranks per minute)
- Wheel circumference
By multiplying the gear ratio by the RPM, one finds the total rotations of the rear wheel per 1 minute.
If we multiply them by the wheel circumference, we find the total distance traveled by the bicycle in one minute. Once we have those numbers, we can easily find the speed.
The formula for speed is speed = distance/time.
A lower gear ratio, on the other hand, is beneficial when it comes to climbing because the rear wheel has to perform fewer or not even one full rotation per 1 spin of the cranks.
For instance, if the smallest ring has 22 teeth and the largest cog has 36, the gear ratio is 22/36=0.61.
To offer the same gear range, 2×11 will need a larger cassette that will have bigger transitions between the gears.
- Affordable
3x drivetrains not only offer a wide gear range but do so at a very low price. Hence their presence on the vast majority of entry-level bicycles. That doesn’t mean that there aren’t high-end 3x setups, but they aren’t as common.
Since the drivetrain of a bicycle doesn’t have as much of an impact on performance as the frame, wheels, and suspension, people on a budget could save money by going for a less shiny choice.
It’s better to have a nice wheelset and suspension coupled with a cheap 3x drivetrain than the latest 1×12 setup on an otherwise mediocre machine.
- Reliability
3x drivetrains of acceptable quality are very reliable. If one of the chainrings is damaged, the rider can use the other two even though the gear combinations won’t be ideal for every terrain.
- Perfect Chain Line
With proper shifting 3x drivetrains minimize cross-chaining and ensure efficient pedaling.
The Disadvantages of 3×9
- Redundant Gears
In theory, 3×9 gives you 27 gears. But in practice, some of those gears are redundant and not very practical. For example, it makes little sense to put the chain on the largest chainring and the largest cog.
The cross-chaining will be extreme and the gear ratio can be obtained by using the middle chainring in conjunction with a cog close to the middle of the cassette.
2×11 greatly reduces the redundant gears and makes up for a neat and yet very usable drivetrain.
- Low Quality
3x drivetrains are mass-produced and built for entry-level bikes. For that reason, companies have a low incentive to implement the latest technologies.
- Extra Weight
When all parameters are equal (material, quality…etc.), 3x is ever so slightly heavier than 2x. However, the discrepancy is very small and the extra weight is in the middle of the bike where it has the smallest impact on performance.
The Advantages of 2×11
- Wide Range Without Redundancy
The main incentive to go for 2×11 is the reduced number of redundant gears.
The table below contains the gear ratios of a 2×11 drivetrain consisting of 26/36 chainrings and an 11-42 cassette with an 11-13-15-17-19-21-24-28-32-37-42 gradation.
| Chainring | 26 | 36 | |
| Cog | |||
| 11 | 2.36 | 3.27 | |
| 13 | 2.00 | 2.77 | |
| 15 | 1.73 | 2.4 | |
| 17 | 1.53 | 2.12 | |
| 19 | 1.37 | 1.89 | |
| 21 | 1.24 | 1.71 | |
| 24 | 1.08 | 1.50 | |
| 28 | 0.93 | 1.29 | |
| 32 | 0.81 | 1.13 | |
| 37 | 0.70 | 0.97 | |
| 42 | 0.62 | 0.86 |
The bolded gear ratios indicate gears that are close to each other and thus somewhat redundant.
The next table shows the gear ratios of a 3×9 drivetrain equipped with 42/34/22 chainrings and an 11-36 cassette with an 11-13-15-18-21-24-28-32-36 gradation.
| Chainrings | 42 | 34 | 22 |
| Cogs | |||
| 11 | 3.82 | 3.09 | 2.00 |
| 13 | 3.23 | 2.62 | 1.69 |
| 15 | 2.80 | 2.27 | 1.47 |
| 18 | 2.33 | 1.89 | 1.22 |
| 21 | 2.00 | 1.62 | 1.05 |
| 24 | 1.75 | 1.42 | 0.92 |
| 28 | 1.50 | 1.21 | 0.79 |
| 32 | 1.31 | 1.06 | 0.69 |
| 36 | 1.17 | 0.94 | 0.61 |
As shown above, 3×9 comes with many more redundant gears.
- Simpler
2×11 is a simpler setup. The rider has to choose only between two chainrings. It is also more aesthetically pleasing according to some.
- Lighter
As already mentioned, 2×11 has the potential to be ever so slightly lighter.
- Higher End Components
2x drivetrains are considered mid-range. Thus, the user can find components of better quality.
The Downsides of 2×11
- Pricier
2×11 cannot beat the affordability of 3×9. Every part of the 2×11 drivetrain tends to cost more – from cassettes to shifters.
- Lower Top Speed
Unless you have a road bike, 2×11 setups are rarely equipped with chainrings that have over 40T. The goal is to keep the gearing balanced. As a result, the top speed of the bicycle suffers.
Summary: What You Need To Know
The pros of 3×9:
- Wider range
- Cheaper
- Reliable
The cons of 3×9:
- Lower end parts
- Redundant Gears
- Slightly Heavier
The pros of 2×11:
- Wide gear range
- Fewer redundant gears
- Simpler to use
- Lighter
- High-end components
The cons of 2×11:
- Smaller gear range
- More expensive
