Choosing the Best 1x Gearing for Your Fitness & Terrain

Thanks to their simplicity and reliability, 1x drivetrains have become one of the most popular drivetrain options for gravel cycling. One of the most useful aspects of a 1x drivetrain is how easy and affordable it is to modify and fine-tune your bike’s gear range by swapping to a larger or smaller chainring. There’s no front derailleur to adjust; in some cases, you don’t even need to adjust the length of your chain. Some riders even keep different chainrings on hand to adjust their gearing for different rides!

Picking the right 1x chainring size will give you the ideal gearing for your local terrain and riding goals, allowing you to comfortably handle your toughest climbs and fastest descents. OBED is all about giving our riders the perfect bike, so if you need a different chainring size than stock, reach out to us, and we’ll work to get you exactly what you need. But if you don’t know, how do you figure out what size chainring you need? Gear up with this easy guide. 

Shop Gravel Bikes

1x Gravel Bike Gearing Explained 

What Are the Standard Gravel Chainring Sizes?

1x chainrings come in 2-tooth increments. Gravel chainring sizes can range from 36t to 48t, but many 1x gravel bikes will come from the factory with a “standard” size chainring. Depending on the groupset and manufacturer, 40t or 42t chainrings are generally the standard size. These sizes became standard because they mirror the size of the middle (and most used) chainring in older 3x drivetrains. 

Examples: An OBED GVR with a Shimano GRX 1x group or SRAM Force AXS XPLR group will come with a 40t chainring. If equipped with a SRAM Rival AXS XPLR group, it comes with a 42t chainring. 

Why Change to a Smaller or Larger Chainring?

• A smaller chainring provides easier climbing gears

• A larger chainring provides higher top speeds

Standard 40t and 42t chainrings work for a lot of riders in common riding situations, but many may find that they want a smaller or larger chainring to match their terrain, goals, or fitness level.

Smaller chainrings provide easier gearing for tackling tough climbs and hauling more weight. They tend to suit gravel bikes intended for more rugged terrain, adventure riding, or bikepacking. 

Larger chainrings allow riders to achieve and hold higher top speeds, and they are marginally more efficient at high speeds because the chain has to articulate less, reducing chain friction. They tend to suit more racing-oriented gravel bikes. 

1x drivetrains are all about finding the perfect compromise, and finding your perfect gearing might require a bit of experimentation. If you already have a chainring on your bike, then you can use that as a starting point to decide which direction to go. If you’re struggling on hills and climbs, go smaller. If you’re spinning out on fast rides, go larger. (We’ll explain in more detail below.)

Common 1x Cassette Options

OBED Ambassador Austin Sullivan combined a 10-52t cassette with a 40t chainring to have easier gearing for the tough Transcordilleras stage race. 

• Shimano GRX 11-speed: 11-40t

• SRAM XPLR 12-speed: 10-44t

• SRAM XPLR 13-speed: 10-46t

• Shimano GRX 12-speed: 10-51t

• SRAM Eagle AXS: 10-50t or 10-52t

When choosing a 1x chainring, it’s also important to consider the gear range of the cassette used on your drivetrain. The cassette range is the spread between the smallest and largest cog. In the examples above, a 11-40t cassette has a much narrower range than the 10-52t cassette. In general, a narrower range cassette provides smaller steps between each gear, which might appeal to racers or riders who mostly ride flat terrain. Wider range cassettes provide easier climbing gears, which might appeal to riders who ride more mountainous terrain. 

The current XPLR 12-speed and 13-speed cassettes are some of the most versatile and popular options on the market, and they should provide enough range for most riders on flat to hilly terrain. 

If you live in a mountainous region and need the easiest climbing gear possible, or you want to run a larger chainring without sacrificing easy climbing gears, choosing a drivetrain that uses a larger 10-50t, 10-51t, or 10-52t cassette will give you what you need. OBED currently offers GRX 12-speed with the 10-51t cassette, and if you’re interested in using a SRAM Eagle AXS “Mullet” setup with the 10-50t or 10-52t cassette on your OBED gravel bike, reach out, and we can help you out. 

How to Select 1x Gearing for Your Fitness and Terrain

• Is your lowest gear easy enough for your hardest climbs?

• Do you “spin out” on fast descents or when trying to stick with fast riders?

• How often is your chain in the center of your cassette? 

Is Your Lowest Gear Easy Enough?

Smaller chainrings are a good upgrade for riders who struggle with climbing, who regularly ride steep terrain, or who need to carry extra weight like bikepacking bags.

The small change of swapping from a 42t to a 40t chainring, for example, gives you a lowest gear that is 5% easier. That 5% could be the difference between conquering a steep climb and being forced to get off and walk. A 38t or 36t chainring will provide an even easier low gear that should get most riders up anything. Whatever you choose, riding a bike is supposed to be fun, and successfully cleaning a climb is always more fun than hiking. For most riders, choosing the chainring that lets them enjoy climbing the most is the best option. 

Our suggestion: a 40t chainring is ideal for most average riders who want good gearing for climbing. If you struggle more with climbing, then consider sizing down to a 38t chainring.  

Do You “Spin Out”?

Bigger chainrings are great for riders who need more top-end speed or who ride fast on mostly flat or rolling terrain. 

You generally know you need a larger chainring if you’re “spinning out” regularly during your rides. Spinning out is the sensation that occurs when you reach a speed where you can no longer pedal to accelerate. You’re out spinning your legs as fast as possible, but you’ve run out of gears. This can happen if you regularly hit high speeds (30 mph or faster) or if you’re just super fit and strong.  

With a 42t chainring, hitting 30 mph requires a cadence around 90 rpm in the hardest gear. For most riders, that’s more than enough. Look at pro gravel racers, though, and you’ll see many use bigger chainrings in the 46t-48t range. That’s huge! Many high-level amateurs will often choose chainrings in the 44t-46t range. High-level racers are fitter and faster than the general population, so they need to achieve and sustain higher speeds to compete with other riders at their level. Maybe that’s you. 

Our suggestion:A 44t-46t chainring will work great for fit amateur racers or riders going super fast on flat or hilly terrain. A 48t chainring is ideal for high-level riders and racers. 

Are You Staying In The Center Of Your Cassette?

The final consideration is a bit nuanced. One of the drawbacks of a 1x drivetrain is the high chain angle at the extremes of the cassette (the easiest and hardest gears). When the chain isn’t straight, there’s a bit more friction, which leads to a slight drivetrain efficiency loss.

Choosing a chainring that allows you to stay in the center of the cassette more often and maintain a straighter chainline maximizes drivetrain efficiency. For strong riders who are able to hold high average speeds, bigger chainrings can help them keep their chain in the middle of the cassette more often, instead of smashing away in the less efficient small cogs at the end of the cassette.

Ultimately, though, unless you’re exceptionally fit, these small efficiency increases probably don’t matter. Most riders are better off prioritizing their easy climbing gears and using the smallest chainring possible.   

Our suggestion: Only worry about this if you’re racing competitively. 

Final Thoughts

With smaller (40t or less) chainrings, you may find yourself spinning out on fast downhills, but for me, the risk of spinning out is always preferable to being overgeared on climbs. Easier climbing gears keep my legs fresh and allow me to tackle ambitious rides. For regular riders, saving energy and preserving your knees through high-cadence spinning and completing tougher routes will improve the gravel riding experience. 

FAQ: 1x Chainrings and Gearing

Do You Change Chain Length When Swapping Chainrings?

As a general rule, you can usually change the size of your chainring by 2 teeth larger or smaller without changing your chain length. If you go more than 2 teeth smaller than your current chainring, you might need to shorten your chain. More than 2 teeth bigger, and you'll need to add chain links or get a new, longer chain. 95% of the time, your rear derailleur will have enough b-gap/b-tension adjustment to compensate for a 2-tooth change. However, there are always edge cases.

First, always adjust the b-gap/b-tension of your rear derailleur after changing the size of your 1x chainring. You'll know your chain is too short if it pulls your rear derailleur into an extreme angle when shifted into the lowest gear. The rear derailleur will be pulled so tight that it is nearly horizontal and can no longer articulate. You'll know your chain is too long if there’s excessive slack in the chain when shifted into the hardest gear. The chain will be loose, causing it to bounce around and hit your frame.

What’s the Best Online Bike Gearing Calculator?

Gear calculators are great tools for comparing different chainring options. To calculate the percent difference in gearing between different-sized chainrings, I like to use Sheldon Brown’s classic gear calculator. Seeing the difference as a percentage convinced me that it was worth switching from a 42t to a 40t chainring on my gravel bike to improve my climbing. 

Another favorite is gear-calculator.com. It provides a nice visual comparison of different gearing options that you can compare. This is a nice tool for figuring out the minimum and maximum speeds of your setup by selecting the applicable gearing, tire size, and cadence. This is how I determined you can hit 30 mph at 90 rpm with a 42t chainring (which I’ve also verified in real life). 

What About The Best 1x Chainring Size for Road Bikes?

1x road bikes aren’t exactly common (yet), but bikes like the OBED RVR are the perfect platform for 1x road experimentation. (Let us know if you want to try that on your own build!) Road bikes have the same or similar chainring size options as 1x gravel bikes, but in general, road bikes will likely need a slightly larger 1x chainring than gravel bikes, as they are often ridden at higher average speeds.

If you already have experience riding a 1x gravel bike, I'd suggest starting with a chainring that is 2-4 teeth larger than what you are used to on your gravel bike. If you're starting from scratch, I'd consider starting out with a 46t chainring. If you have a modern 11 or 12-speed cassette with a 10t small cog, the top gear (46x10t) will be roughly between the top gear found on traditional compact (50x11t) and mid-compact (52x11t) road drivetrains. Stronger riders and racers can consider trying a larger chainring in the 48t-52t range. 

Shop Gravel Bikes