Updated July 2nd, 2023
What is up with all the single front gear mountain bikes? Most mid to high priced mountain bikes now come with single chainring or 1X drivelines. The front derailleur has disappeared. This gives us fewer gear combinations.
We used to have 27 speeds with a 3×9 driveline. Now we have only 10,11 or 12 speeds with 1x drivelines. Fear not. 1X drivelines have a lot of advantages and very few disadvantages over 2 or 3 front gear mountain bikes.
Let’s take a closer look at single front gear mountain bike drivelines below.
What is a 1X or Single chainring driveline?
A 1X or “OneBy” driveline only has a single chainring gear on the crank. It has no front derailleur. These systems tend to come with 10, 11, or 12 gears on the rear cassette. They are all 10, 11, or 12 speed. Occasionally you will see a new bike that has a 9 speed cassette and only nine speeds. They aren’t very common.
Advantages of Single Front Gear Mountain bikes
The first advantage is obvious. You have no front derailleur or front shifter. There are fewer parts to go wrong. The front derailleur may be the single hardest part on a mountain bike to adjust correctly. You save a little weight by removing these parts plus the shifter cable. The front derailleur shifts from the half the chain that is loaded up while pedaling. It only shifts well when you aren’t pedalling hard. By removing this, it’s one less thing for a new rider to worry about. For some riders like my wife, they never really understand shifting chainrings or when to do it.
Disadvantages of Single Front Gear Mountain Bikes
The biggest disadvantage of single front gear mountain bike drivelines is the gear range. This means that you either have less low gear or less high gear then you had with a 2 or 3 chainring driveline. The 12 and 11 speed systems with 10-50 and now 10-52 tooth cassettes has almost the range of a 2 or 3 chainring system. The 10 speed systems with 10-42tooth rear cassette give up several gears worth of range. It’s common to lose both a high gear and low gear relative to a 2 chainring driveline.
The below video has a comparison between 1X and 2X drivelines for trail riding.
Where did 1X drivelines come from?
In the 1980’s when mountain bikes first became popular they had 3 chainrings and 9 rear cog gears. This was the standard setup for a long time. Some guys rode single speed bikes for something different so single gear crank parts were out there.
Somewhere around 2010 2x drivelines came out that had 2 chainrings and 10 rear cogs. These were great. You could almost do an entire trail ride on the low chainring and save the high chainring for pavement or the occasional long downhill.
Some guys got innovative and realized they barely ever used the second chainring and got rid of it. The 1X driveline was born. From there component companies SRAM and Shimano started producing dedicated 1X drivelines. They started out with 11 speed and then moved to 12 speed as well. They started selling 10 speeds also with “wide range cassettes” which had 11-42 and 11-42 tooth cogs.
How do I convert my mountain bike to a single chainring?
The good news is that there are a bunch of ways to convert your double or triple chainring mountain bike into a 1X mountain bike. The first thing is the chainrings. You can either replace the crank with a 1X crank or you can use the existing crank and remove 1 or 2 chainrings.
It is helpful to use a chainring called a “Narrow Wide” ring. These have alternating narrow and wide teeth to match the tooth spacing in the chain. This helps keep the chain from dropping. Some people find they need a chain retainer or tensioner also.
On the rear half of the bike, if you have a 10 speed, you can swap to a wide ratio cassette. If you have a 9 speed you might want to replace your cassette with a 10, 11, or 12 speed and replace the shifter and rear derailleur also. In any case, you should also consider getting a clutched rear derailleur. These have stiffer springs in the tensioning mechanism which help prevent chain drops.
The below video gives some good detail on converting a mountain bike to a 1X driveline.
Mountain Bike 1X Driveline FAQ
Q: Why bikes are being sold with only one gear in front?
These bikes are called 1X or OneBY drivelines. They have only a single chainring and a wider ratio rear cassette. Their advantage is that they don’t have a front derailleur or shifter. The bike is more reliable and you don’t have to worry about shifting front gears before you climb a steep hill.
Q: Can I just remove my front derailleur?
For a short answer. Yes. You can remove the front derailleur and have a 1X driveline. You will probably find you don’t have enough high or low gear with the rear gears the bike came with. A double or triple chainring bike won’t have a wide ratio rear cassette. You may also find that your bike drops the chain a lot. You won’t have a narrow wide chainring or clutched rear derailleur. Go ahead and give it a try. This is exactly how people created the first 1X drivelines.
Q: Are 1x drivetrains worth it?
Yes. They are worth it. If you have ridden an SRAM Eagle or Shimano 12 speed system you will understand how great a 1X driveline can be. No chainring shifting. All the range most of us will use. Dropped chains are rare. The shifting is really smooth. I’ve been riding an Eagle GX system for a couple of seasons now and love it. I will never go back to a bike with a front derailleur.
Q: How do I convert my mountain bike to 1x (single chainring) ?
The simple answer is just to remove the front derailleur and shifter. The complicated answer is to replace the front crank, get a narrow wide chainring, get a wide range cassette, and get a clutched rear derailleur. Depending on what you want to do and what your bike started with it can be cheaper or more expensive.
Q: Is 1×11 better than 2×10?
A 1×11 driveline will have less range than a 2×10 driveline. With the new 11-50 11 speed rear cassettes, you will give up 1 gear relative to a 2 x 10 driveline. You will either lose the very lowest gear combination or the very highest gear combination. If you have a 11-46 cassette on your 1×11 you will give up 2 gears. Either the lowest and higher, the 2 highest or the 2 lowest. If you have an 11-42 rear cassette you give up 3 gears relative to the 2×10 system.
At the same time, you get rid of the front derailleur and front shifter. For many riders that is enough of an advantage.
Q: Why do mountain bikes only have 11 gears now?
A few years ago 11 speed, single chainring systems were common on midrange mountain bikes. 12 speed systems have no gotten cheap enough that many of the bikes that were 11 speed are now 12 speed. I personally believe that 1X drivetrains will keep showing up on lower and lower priced bikes.
I believe we will see them soon even on Walmart store level bikes. I can’t believe that tripple chainring drivelines are cheaper to manufacture than 1X. You get rid of a lot of parts for 1X and the rear derailleurs and cassettes aren’t more complex.
Q: How do you stop a chain slap?
A clutched rear derailleur will cure most of your chain slap woes if you did a 1X conversion. They have much stiffer springs in their tensioning mechanism. This keeps the chain tighter preventing it from slapping on your chainstays.
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Co-Founder & Chief Editor
I grew up back east in Pennsylvania and learned to ski on a family trip to Killington, Vermont when I was 6. I immediately fell in love with the mountains and outdoors and have been skiing across the US and Canada ever since. I went to school for Mechanical Engineering, and have a Master’s Degree in Material Science and Reliability.
I am a total gear nerd and love learning how things work and thinking about how they could be improved. Nothing excites me more than trying out new gear. I’d rather spend 3 hours taking my bike apart and learning how to change something than go to a bike shop. These days I reside in Michigan by the Great Lakes and go skiing, biking, and boating as much as possible.