Bike Drivetrain 1x Conversion Pros & Cons

Modern 1x mountain bike drivetrain conversion.

OK, so you've found your ideal bike but it only comes with a two-by (2x) drivetrain. You want a one-by (1x). All the cool kids have a 1x.

Should you leave your bike how it is and not be cool, or should you chug out an extra grand for a conversion?

I'm going to go against the cool kids here. I own a fat bike after all. What do you expect?

2x versus 1x bike drivetrain - Should you upgrade or not?

There's a lot of hype about bikes 'needing' to be 1x, but honestly, if you have a 2x setup, or even an old school 3x setup, unless your main gig is only climbing hills at the bike park all day AND you need to peel off every gram possible AND you have a ton of money to spend on the very best level of 1x componentry AND you can afford to replace it every year or so, stick with what you have.

I did buy into that hype for a bit, though with niggling doubts, and converted all my mountain bikes and the fattie from 2x10 to 1x11.

In hindsight, I should have trusted my instincts - and maths - and not done it. A 1x setup means compromise. You do lose versatility. Progressively, I'm changing all my bikes back to 2x, and these are the reasons why.

Shimano XT long cage 1x11, 36T chain ring, 11-50T Sunrace MX80 cassette
Original fitment: Shimano SLX medium cage 2x10, 36-24T chain rings, 11-36T SLX cassette
Shimano XT long cage 1x11, 36T chain ring, 11-50T Sunrace MX80 cassette
After conversion: Shimano XT long cage 1x11, 36T chain ring, 11-50T Sunrace MX80 cassette. I have since swapped the 36T chain ring for a 32T oval Wolf Tooth to recover its hill climbing ability but now I've lost 12% top end on downhills and straights. I'm going back to 2x.

Arguments for 1x set up:

So, what are the reasons to upgrade?

Bike makers have adopted 1x so it must be better.

Of course bike manufacturers have adopted 1x. They no longer have to provide a front derailleur, cable, or shifter. Funny how the cost hasn't gone down though.

Weight reduction

Well, my answer there is that unless you have the absolute top level 1x setup, the weight reduction is minimal.

Sure, you lose the front derailleur, shifter, inner chain ring, and cable - say you lose 250 grams. But then you have to add a heavier cassette because you need bigger rings, and extra chain links - say you add 200 grams.

Wow, massive saving. Not.

I actually did the maths on it when converting my Shimano XT 2x to XT 1x. The saving was 38 grams.

Even if you do go to the top of the range stuff - and sure you will save 300-400 grams for that $1500 plus dollar upgrade - bear in mind that weight reduction also means strength reduction.

Fat Bikes for XC Racing

They climb better

Rubbish. Say you swap out your front chain rings for a 34T which is pretty common and you throw on a big 50T ring on the back. That's just a bit shy of 3:2 ratio - Pedal 3 times to turn the wheel twice.

OK, so you've swapped that for your old 2x setup, which likely had a 24T lower chain ring and a 38T big chain ring. Your old cassette may have had up to a 42T ring but let's be conservative and say it was a 36T. Well, 36:24 is a 3:2 ratio, slightly better than your 34:50.

Sure, you could go to a 32T or 30T chain ring, but equally you could just chuck a 42T cassette on your 2x setup and yet again your 1x is outclassed.

Before anyone argues that a small chain ring on a 2x creates more directional friction than a large chain ring, that power loss is around 1 - 1.7 watts, roughly the same as is lost from lateral friction on a 1x. *Friction Facts - Bike Radar

Less cockpit clutter

Seriously? When did this become a thing? They're cables. Get over it. I've got seven cables/sheaths on my Scott Genius - 2 brakes, 2 derailleurs, 1 dropper, and 2 remote suspension levers - and they don't bother me at all. Still plenty of room for dual headlights and my Wahoo.

Chain doesn't fall off as much

This issue is imaginary for most riders. My chain used to fall off maybe once a year. It rarely happens, but if it does, buy a Black Spire chain retainer. Twenty bucks on eBay. In fact, get one even if you're chain doesn't fall off - They look super cool - Get a red one.

Shimano XT medium cage 2x10 drivetrain
2016 Scott Genius: Shimano XT medium cage 2x10, 36-24T chain rings, 11-36T XT cassette. Everything kept nice and tight with a Black Spire chain guide

Less chain slap

A fair point. A 1x does have less chain slap because the derailleur has a clutch. That said, you can do what you've always done i.e. wrap a bit of old tube around your chain-stay and hold it on with zip ties so the chain doesn't hit the frame. Or as above, a Black Spire will fix that too.

Less thinking required

Um. When you're climbing, use the small chain ring. When your descending, use the big chain ring.

Arguments against 1x set up:

Lateral friction

On a 1x setup, the chain is expected to move laterally across anywhere from 11 to 13 gears. The angles can look really scary up on the big rings.

Given that one of the key arguments for 1x setups is efficient uphill climbing, you can hear the gears grinding once you add some dirt, sand or mud to your chain links.

In contrast, a 2x 11-speed is only expected to cross about 7 gears per chain ring. I countered the directional friction argument earlier, but another is derailleur friction.

The fact is, if you're getting front derailleur friction, it isn't adjusted properly. A $10 chain guide can also negate that problem.

Top end speed

Riding isn't all about climbing. What rides up must ride down. Sure, there's that wonderful cliche that XC races are won on the climbs, but that's not utterly true.

You do need top end. On a 1x setup, the compromise of a small front ring means that on the flats or downhill, you pedal your butt off to a frenzy and you're barely moving.

I regularly hear 1x riders complain that they've run out of gears. If you've got the legs, a 2x with a big 38 on the front will pull away from the pack every time.

Don't get me started on 3x's with a 48T ... hmm, I do have a complete 3x9 XTR drivetrain sitting in my parts cupboard ...

Derailleur exposure

If you need to change to a long-cage derailleur as I did in order to accommodate that big 50 tooth jobbie, you're more prone to it striking obstacles on the trail.

Brownie Points

You won't have an argument with your better half trying to justify why you spent a grand on something that might not end up making sense.

And that's pretty much the crux of it.

It's five years since I first wrote this article in 2019. In the intervening years (don't mention the virus), we've seen the advent of wider range 1x systems from Sunrace and SRAM.

With the introduction of Microspline hubs, Shimano have also played catch-up with 10x51 cassettes. E-thirteen and ZTTO even offer 9 tooth small rear cogs for lovers of top end speed.

Monster Gravel Bikes

All of that is an attractive proposition BUT I still wouldn't rush out to convert an old bike or lower specced model of a new bike - many of which continue to offer 2x drivetrains.

The conversion costs have become even more prohibitive than before, and the advantages/time savings are minimal by comparison.

Now it's up to you. I hope I've given you some food for thought. 😉