• Jamie

Opinion: 1x drivetrain? Why not make 2x better instead?

Updated: Jan 12, 2020

2x vs 1x, chainrings, drivetrain, crankset, road bike
A 16-tooth difference is currently the limit for road 2x chainsets, but is there scope for development?

Something is missing from the 1x versus 2x debate and it’s this: Are 1x drivetrains the only way forward? Have 2x drivetrains reached their limit or could groupset manufacturers develop them further?

Aside from electronic shifting, the technology in the front end of your drivetrain has been virtually stationary for decades. We’re stuck with the same maximum 16t size difference as has existed for ages (or 17t in the case of the new, gravel-specific Shimano GRX) and it’s precisely this that limits the scope of a 2x drivetrain and leaves the door open for 1x to offer the alternative.

A 2x11 drivetrain (50/34, 11-28) gives you 15 non-overlapping gears because only the top four sprockets are lower than your 50x28. If you could push the chainrings out to 53/30 you would increase your total to 17 distinct ratios and, most usefully, the extra two would broaden the total range, one at each end. You’d have the racer’s 53x11 for sprints and descents and a super-low 30x28 (near identical to 34x32) for climbing, and all without resorting to a huge, gappy cassette. And there's no way that we're ever going to see a 17-speed cassette, or even 15. There simply isn't enough room back there.

1x cassette, SRAM, drivetrain, wide range
A wide cassette can give 1x the same range as 2x, but at the cost of bigger gaps between gears

Right now it isn’t possible, but I’m inclined to think that’s because no one is trying. All the focus has been on adding the next sprocket to the cassette and gadgety features to electronic shifting. It wasn’t so long ago that we were told 9-speed cassettes were the limit. The industry has achieved so much that I can’t believe no one can figure out how to make a chain shift smoothly across a bigger gap.

I’m not an engineer, but here’s how I think it might work:

• outer chainrings with intermediate teeth as well as ramps, almost like a middle ring, to help the chain climb up and maintain power transfer while doing so

• for electronic shifting only to make shifts powerful and consistent

• use a crank position sensor so that shifts only begin when the ramp teeth are in the ideal place

Just a thought. I reckon it would solve a lot more problems than losing three gears by going 1x.

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