1x12 Drivetrain

With a large cassette up to 51t, a 1x12 drivetrain climbs any hill and has enough speed to go as fast as you want.

Gravel bikes paved the way for 1x systems, desiring simpler drivetrains and not caring as much about steps in cadence. The additional gears makes that less of an issue anyway.

New freehub types

New hub types from Shimano (microspline) and Sram (XD) allow for a 10t top gear. This lets you have a smaller max chainring in front, which fits closer to the frame.

It is still possible to run 12 speed drive trains on older 8+ speed wheels using aftermarket cassettes. See Sunrace or ZTTO. These will have an 11T low sprocket.

Front Chainring

For a 11-51T cassette, choose a chainring that will get you up the steepest hill, but go as fast as you want. Use a gear ratio calculator to compare with a familiar drivetrain and try it out.

I had a 46T big ring on my cyclocross bike and the times that I maxed out the 11T cog was going down hill and it was definitely enough speed. I think I could drop down to a 40-44T cog if needed and riding more offroad. Smaller rings would be for much less road use.

Many frames will need to carefully match the largest size chainring available without hitting the chainstay.

Cranksets

There are a variety of crankset sizes now to fit frames from road to mtb to mtb boost.

Check the Q factor on the cranks to ensure clearance with your frame and avoid extra wide cranks or it will look goofy.

MTB cranksets will typically come with smaller rings, and it may be hard to find touring/gravel size rings for it.

You will also need to match the front derailleur and shifter to the crankset's rings. Although there is a lot of flexibiity here.

Featured 1x12 derailleurs

Featured 1x cranksets