The 1x drivetrain, long reserved for mountain biking, has become increasingly popular in gravel cycling and is now starting to appear on some road bikes, notably through SRAM's XPLR groupsets. Many cyclists mistakenly believe that a 1x drivetrain requires a "special chain". In reality, the technical difference lies almost entirely elsewhere: in the chainring and cassette, not in the chain itself.
This guide explains what really changes between a 1x and a 2x drivetrain. For general information on choosing a bicycle chain, see our guide to choosing your bicycle chain.
1. The context: the rise of 1x drivetrains on road and gravel bikes
The 1x drivetrain simplifies the transmission by removing the front derailleur: a single chainring at the front and a wide-range cassette at the rear to provide a sufficient range of gears. Originally developed for mountain biking to reduce the risk of chain drops on rough terrain, the concept quickly gained popularity in gravel cycling, where varied terrain calls for the same combination of simplicity and reliability. On pure road bikes, 1x remains a minority choice but is gaining ground, notably thanks to SRAM's XPLR groupsets.
2. The chain itself: is there really a difference?
Key point to remember: at the same number of speeds, the chain used on a 1x drivetrain is most often exactly the same reference as the one used on a 2x drivetrain. On road bikes, there is no such thing as a "1x chain" with a fundamentally different geometry. The technical difference lies almost entirely in the chainring and cassette, not in the chain.
This point is worth clarifying because many cyclists mistakenly believe that switching to a 1x drivetrain means changing to a different type of chain. In practice, a 12-speed chain remains a 12-speed chain, whether it is used on a 1x or 2x drivetrain from the same brand and generation.
3. The role of the narrow-wide chainring in chain retention
Without a front derailleur to help keep the chain aligned, the risk of the chain dropping from the chainring increases, particularly when riding over bumps and uneven terrain. To compensate, 1x chainrings use a so-called "narrow-wide" tooth profile: the teeth alternate between narrow and wider profiles, precisely matching the alternating inner and outer links of the chain.
This precise fit greatly reduces lateral chain movement on the chainring, which lowers the risk of chain drops even without a chain guide or front derailleur. It is this specific chainring tooth profile — not the chain — that represents the key technical innovation of the 1x drivetrain.
4. Cassette and gearing: the real difference in the drivetrain
To compensate for the absence of a second chainring, 1x drivetrains use cassettes with a much wider range than those typically found on a 2x drivetrain (for example, 10-36 or 10-44 teeth, compared with 11-28 or 11-30 on a 2x setup). This wider range means that the chain has to operate at more pronounced angles in the extreme positions (smallest or largest sprocket), which places different demands on the chain without requiring a different chain reference.
5. 1x vs 2x comparison table
| Criterion | 1x Drivetrain | 2x Drivetrain |
|---|---|---|
| Simplicity | Single chainring, no front derailleur | Two chainrings, front derailleur to adjust |
| Weight | Lighter (no front derailleur) | Slightly heavier |
| Gear Range | Narrower for pure road use | Wider and more progressive |
| Risk of Chain Drop | Reduced thanks to the narrow-wide chainring | Higher without a properly adjusted front derailleur |
| Maintenance | Simplified (only one chainring to monitor) | Standard, with two chainrings to check |
| Compatible Chain | Same as the 2x setup with the same number of speeds | Identical |
Green rows = clear advantage for the 1x drivetrain · orange row = main point to consider with 1x on the road.
6. Advantages and disadvantages of a 1x drivetrain on the road
Advantages: a drivetrain that is easier to maintain and adjust, reduced weight, a lower risk of chain drops thanks to the narrow-wide chainring, and faster gear changes since there is no longer a choice of chainring to anticipate.
Disadvantages: the gear range remains narrower than that of a well-spaced 2x drivetrain, which can be noticeable on demanding mountain routes or for riders looking for a very progressive pedalling cadence. The gaps between sprockets on a wide-range cassette are also more pronounced than those of a typical 2x cassette.
7. When to choose 1x and when to choose a 2x drivetrain
| Rider Profile | Recommendation | Why |
|---|---|---|
| Gravel, mixed road/trail rides | 1x Drivetrain | Greater reliability on uneven terrain |
| Pure road riding, demanding hilly terrain | 2x Drivetrain | More progressive gear range for climbing |
| Looking for simplicity and reduced maintenance | 1x Drivetrain | Fewer adjustments, lower risk of chain drops |
| Traditional road racing | 2x Drivetrain | Still the dominant standard, with a wide and finely graduated gear range |