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How do I convert a 3x or 2x drivetrain to a 1x setup?

By Crankworthy · Published · Updated

Short answer

Remove the front derailleur and left shifter, fit a single narrow-wide chainring that matches your crank's mount, and use a clutch rear derailleur. Most conversions also add a wider-range cassette to recover the low gears you lose — which means checking the rear derailleur is rated for its biggest cog.

Where on your bikeChainring and crank, at the bottom bracket

1x chainline seen from aboveTop view: the single chainring sits a set distance from the frame centreline, measured from the middle of the seat tube. It should line up with the middle cog of the cassette, so the chain angles evenly to the largest and smallest cogs.One ring, lined up (top view)frame centrelineseat tubechainlineone ringcassetteto the middle cog
Seen from above, with the drive side at the top. Measure from the middle of the seat tube to the middle of the ring’s teeth; the rear chainline is taken to the middle of the cassette, and on a single ring the two should match (Sheldon Brown, “Chainline”).

What each part does

With no front derailleur guiding the chain, a narrow-wide chainring keeps it on: its teeth alternate thick and thin to match the chain's outer and inner links, so the chain seats firmly on every tooth.

A clutch rear derailleur resists the cage swinging forward over bumps. That keeps chain tension up, which is the other half of keeping a 1x chain from dropping on rough ground.

With one ring instead of two or three, you lose range at both ends. A wider cassette brings the low gears back, but the rear derailleur must be rated for the new largest cog — and the cassette has to fit your freehub.

Chainline matters more on 1x, because the chain has to reach both ends of the cassette from a single ring. With one ring, the front chainline should match the rear one, taken to the middle of the cassette [1]. On a triple, chainline is measured to the middle ring and on a double to the point halfway between the rings [1] — so those are the positions a single ring starts from. Spacers between the ring and the crank spider move it out [1]. Boost frames and cranks are designed around a wider chainline than non-Boost ones.

Choosing the chainring

Bolt circle diameter (BCD)
Measure across the chainring bolt holes, or check your crank's spec. 104mm BCD with four bolts is very common on mountain cranks and takes a single ring on the existing spider.
Direct mount
Some cranks have no spider; the ring bolts straight to the crank arm. These need a direct-mount ring made for that crank family, such as Shimano's or Race Face Cinch.
Tooth count
Smaller rings climb more easily; larger rings go faster at the top end. Around 30–32T is a common starting point for trail riding with a wide-range cassette.
Measuring chainline
Measure from the middle of the seat tube to the middle of the chainring's teeth — or from the near side of the tube and add half its diameter [1][2]. Compare with the chainline your crank and frame are designed for, which the manufacturer lists.

Skip

Don’t buy: an ordinary chainring for a 1x
Instead: a narrow-wide ring that matches your crank’s mount.
Don’t buy: a wide-range cassette before checking the derailleur
Instead: look up your rear derailleur’s largest rated cog first.

Bikes this applies to

From our research, these bikes come with two or three chainrings — the setups a 1x conversion starts from.

Narrow-wide chainrings

Single chainrings from our catalog — check the mounting standard (BCD or direct mount) against your crank.

Prices were last checked when the catalog was built and can change at any time. Retailer links are affiliate links; we may earn a commission at no extra cost to you.

Sources

  1. Sheldon Brown — Chainline
  2. Park Tool — Chainline Concepts

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