A growing trend in cycling is the oval chainring (also known as an elliptical chainring). This unique piece of gear is gaining popularity among road cyclists, mountain bikers, bicycle tourists, and commutes. This guide analyzes the pros and cons of an oval vs round chainring to help you decide whether or not it’s worth your time to try one out.
Oval chainrings are also a bit controversial. Some cyclists love them and others can’t stand them. In this guide, I’ll also attempt to resolve some of the biggest controversies surrounding oval chainrings including whether or not they improve performance and efficiency and if they cause knee pain. We will do this by looking at what science has to say.
What Are Oval Chainrings?
As the name suggests, oval chainrings are chainrings that are shaped like an ellipse instead of the standard circle. This shape effectively changes the gear ratio as you pedal.
In theory, an oval chainring allows you to deliver more power by making it easier to ride in a higher gear. This improves efficiency as well. Some cyclists also believe that they are easier on the knees. More on that later.
How Do Oval Chainrings Work?
Due to the elliptical shape, the radius of the chainring increases and decreases as you pedal. Classical oval chainrings were designed so that when the pedals are vertical, the radius is shorter on the part of the ring where the chain sits. When the pedals are horizontal, the radius is longer on the part of the ring where the chain sits.
This effectively changes the gearing as you pedal by varying the size of the chainring. When the smaller radius section of the chainring engages, pedaling becomes easier. When the larger radius section of the chainring engages, pedaling becomes harder. For example, an oval chainring with 32 teeth effectively changes between a 30 tooth and 34 tooth chainring as you pedal.
The radius becomes larger when the pedals are horizontal. You’re basically pushing a higher gear when the pedals are in their optimal position. This allows you to deliver more power during the power phase of the pedal stroke.
When the pedals are vertical, the gearing becomes lower because of the smaller effective radius. This makes the pedals easier to push through the dead zone. This part of the pedal stroke is often called the recovery phase.
A Bit of History About Oval Chainrings
Oval chainrings have been around for over 100 years. They were first used shortly after the invention of the safety bicycle in the late 1800s. Over the decades since, they have appeared then disappeared again every 15-20 years.
The most significant advancement in oval chainring technology happened in 1983 when Shimano released the Biopace crankset. These don’t use a true ellipse, rather a more complex non-round shape. This design was created with the assistance of computers. A label on the side reads “computer designed drive system.”
Interestingly, Biopace chainrings are designed in the opposite of elliptical chainrings of the past. The radius is smaller when the pedals are horizontal and the radius becomes larger when the pedals are vertical.
Theoretically, this design allows you to speed up your feet when the pedals are horizontal by making the gearing lower. When your feet get to the dead spot, the momentum you’ve built up carries you through. Unfortunately, Biopace was considered a failure and was discontinued in the early 90s.
Oval chainrings started making a comeback in the mid-2010s. These days, a handful of pro road and mountain bikers, as well as thousands of armatures, use them. Modern oval chainrings use the classic design.
Oval Chainring Pros
- Oval chainrings are better for climbing hills than round chainrings- This is where oval chainrings really shine. The hardest part about climbing hills is getting through the dead zone each stroke so you can keep pedaling. Once you manage to push the pedals past vertical, you can use your body weight to keep going at least one more stroke. Oval chainrings make it easier to push through the dead zone. That’s the whole point. For this reason, climbing hills becomes much easier.
- Oval chainrings are more efficient than round chainrings- According to the scientific study Cycling performance improvement with oval chainrings after 1 year of adaptation by Ph.D. Borut Fonda, it was found that, while cycling at 90 RPM, the cyclist saves 5 N every pedal stroke. Over the course of an hour, the rider saves 27,000 N. The article goes on to say, “Based on the results of this study, we can conclude that if using oval chainrings for a longer time, cyclists will spend less energy at a given power output and could potentially ride for longer.” By using less force each pedal stroke, the rider can ride further using the same amount of energy.
- Oval chainrings encourage better pedaling technique- According to the same scientific study linked above, after using an oval chainring for 1 year (3000-1000 km), the riders developed a better pedaling technique. This improved performance and efficiency.
- Oval chainrings deliver power to the rear wheel more smoothly- With round chainrings, you’re putting the most power into the pedals when they are horizontal. The power fades off as the cranks move to the vertical position where pedaling becomes harder. Oval chainrings smooth out that power delivery by essentially changing the gearing as you ride. This way, power is delivered to the rear wheel more consistently rather than in a pulsating manner. Your bike will move at a more even speed.
- Better traction- Because of the smoother power delivery, your rear wheel is less likely to lose traction. The reason is that the power is more constant rather than pulsating. The pulsing power of a round chainring can break your rear wheel loose while riding on slippery surfaces like snow or loose gravel. On stickier surfaces, the bike may wheelie. When your rear wheel spins out, you’re just wasting energy that could be used to drive you forward.
- Oval chainrings may be better for the knees- Some riders find that switching to an oval chainring makes it easier to push through the dead zone, reducing knee strain. I’ll talk more in-depth about knee pain later on in this guide.
- More torque- Oval chainrings focus your pedaling energy where you naturally apply the maximum force to the pedals. This helps to produce more torque. This is the first thing I noticed when I rode my Schwinn High Sierra with a Biopace crankset. The extra torque made it much easier to start from a stop or power up a steep hill.
- Better acceleration- When you’re starting out from a stop, oval chainrings make it faster and easier to pedal through the dead zone. The additional torque helps you power up to speed.
- Oval chainrings make riding technical terrain easier- You don’t have to worry as much about getting stuck in the dead spot. If you bit off more than you could chew, the extra torque allows you to power through places you might have gotten stuck with a round chainring.
- Better for riding at a slower cadence- Oval chainrings are more comfortable and efficient to ride at lower RPMs. In fact, the Biopace designers optimized the chainrings for a cadence slower than around 90 RPM. For this reason, they work better for bicycle tourists, mountain bikers, and recreational riders. At higher cadences, the ride feels a bit less comfortable. The reason is that your legs accelerate and decelerate as you pedal. When you race along at 120 RPM, this motion can feel a bit strange. You also lose some efficiency because you’re not pedaling as smoothly. Clipless pedals may help minimize this problem.
- Adjustable- Some oval chainrings allow you to rotate them in relation to the cranks. This way, you can adjust your crankset to the optimal position for your style of pedaling. To find the optimal position, you can test multiple settings. For example, you may test setting the ring so it sits in its larger and smaller radius position when the crank is vertical. Maybe you want to test it somewhere in between. You can test until you find the optimal position.
- They’re unique- If you enjoy trying out different cycling technologies or riding a bike that’s a bit different than everyone else’s, you may find it worthwhile to give oval chainrings a try. It’s one of those things that you won’t know whether or not you’ll like it until you try it. Before trying an oval chainring, I thought they were pointless. Now I recognize that, while they aren’t ideal for every rider, they do have their place in cycling.
Oval Chainring Cons
- Oval Chainrings may be harder on the knees- This is the biggest argument against them. After all, cycling is meant to be easy on the knees. Some riders complain about a ‘whiplash effect’ causing knee pain from the acceleration and deceleration of the legs as you pedal. I’ll talk more about knee pain in the next section.
- Oval chainrings aren’t ideal for riding at a high cadence- The change in gearing due to the effective radius change of the chainring causes your legs to accelerate and decelerate as you pedal. At higher RPMs the pedaling motion pulses.* Round chainrings feel much smoother at high RPMs because your legs don’t change speed as you pedal. For this reason, many road riders and people who ride at a cadence above around 90 RPM will feel more comfortable with a round chainring.
- There is a learning curve- You immediately feel a difference when you switch from a round to an oval chainring. At first, it feels weird. It almost feels like a walking motion rather than a spinning motion. Most riders get used to the feeling after a few hours in the saddle. Some riders never get used to it.
- Some riders don’t benefit from oval chainrings- Whether or not you experience an increase in power and efficiency depends on your pedal stroke. Riders with a smooth pedaling technique tend not to benefit from oval chainrings because they naturally don’t have much of a dead spot in their pedal stroke. Riders who exert most of their power in bursts while pushing down on the pedals tend to benefit much more. Oval chainrings smooth out the power delivery for these riders. This improves efficiency by reducing the loss of momentum while the pedals are vertical.
- Higher likelihood of dropping your chain- This is only the case if you’re using multiple chainrings. Setting the derailleur limit poses a challenge because the chain moves up and down as you ride. Adjusting your front derailleur becomes a bit tricky. If the limit is off slightly, the derailleur can push your chain off when the largest diameter part of the oval is pointing toward the derailleur. This problem is uncommon but is something to consider on some bikes.
- Scientific evidence shows that oval chainrings don’t offer much benefit over round chainrings– For example, the study Physiological Responses during Cycling With Oval Chainrings (Q-Ring) and Circular Chainrings found that oval chainrings increased power output only 2.5%-6.5%. This is considered statistically insignificant. Having said that, it is still an improvement. Differences in heart rate and oxygen consumption were also minor.
Oval Chainrings and Knee Pain
Oval Chainrings may be hard on your knees. This is the most commonly reported problem and the main argument against their use. Having said this, many riders claim that oval chainrings are easier on the knees and can actually solve knee pain issues.
While researching for this guide, I was able to find one piece of scientific evidence that shows that oval chainrings are not harder on the knees than round chainrings. The scientific study, article Knee Joint Forces in Cycling at Two Workloads with Circular and Non-Circular Chainrings tested three chainrings pedaling at 90 RPM at 180 and 300 watts.
They found that oval chainrings did not put more stress on the knee joints. Pedaling with more power put more force on the knees regardless of the type of chainring used. The study wasn’t conclusive but it didn’t show any signs that oval chainrings cause knee pain either.
In this section, I’ll lay out both sides of the argument to help you decide.
Argument 1: Oval Chainrings Cause Knee Pain
There are two theories about how oval chainrings may cause knee pain. To my knowledge, neither theory has been proven or disproven. They are mostly based on the experience of various riders.
The first theory is that oval chainrings may cause knee pain by encouraging you to push too hard. By design, oval chainrings make it easier to ride in a higher gear by reducing the gearing through the dead zone. You’ll naturally ride at a lower cadence but higher gear because you can. Oval chainrings increase the load on your knee and hamstring at the point in the pedal stroke that you put in the most power. This puts additional stress on your knees which may lead to knee pain. Again, there is no scientific studies to back this up.
The second theory is that oval chainrings cause knee pain because of a “whiplash effect.” The gearing effectively changes as you pedal due to the varying diameter of the chainring. This causes your legs to accelerate when the pedaling becomes easier and decelerate when the pedaling becomes harder. This creates a kind of jerky motion that your knees must endure. Some people call this a “whiplash effect.” Some riders believe that this unnatural motion can cause knee pain.
You can read about a few rider’s experiences with oval chainrings causing knee pain on the singletrack forum.
Argument 2: Oval Chainrings are Easier on the Knees than Round Chainrings
Some riders find that switching from a round to an oval solves their knee pain problems. For some examples, check out this thread from the mtbr forums. Several riders found that the oval chainring helped them get over the top 11-1 o’clock part of the pedal stroke more easily. They claimed that this reduced stress on their knees and pain went away. Some riders claim that oval chainrings smooth out the pedal stroke which reduced knee pain.
The Biopace crankset, in particular, may reduce knee strain by making it easier to pedal during the power part of the stroke. You won’t push too hard and injure your knee. Your legs also slow down before they change direction as the pedaling becomes harder as the cranks approach vertical. This may reduce the whiplash effect and reduce knee strain.
These are only theories though. I have not been able to find any hard evidence to back these claims up. If you suffer from knee pain, it may be worthwhile to give an oval chainring a try.
One thing to remember is that there are a number of factors that can cause knee pain while cycling including seat placement and foot placement on the pedals. Improperly aligned clipless cleats can also lead to knee pain.
Can I Mix Round and Oval Chainrings?
Yes. There is no mechanical reason why you can’t install round and oval chainrings on the same crankset. If you choose to do this, the ideal combination would be for the larger chainring to be round and the smaller chainring to be oval.
The reason this combination is preferable is because oval chainrings are better for climbing hills and riding at lower cadences. While climbing, you can take advantage of the torque and smooth power delivery of the oval chainring.
Round chainrings perform better at high cadences. You can shift to your larger chainring when riding fast or descending hills. On paper, this combination gives you the best of both worlds.
The drawback to mixing round and oval chainrings is that switching back and forth feels strange. This can throw off your pedaling action. For example, maybe you’ve climbed a big hill with your oval chainring then shift up to your round chainring for the descent. After you shift, your body will take some time to adapt to the round chainring. During this time, your pedaling action may be a bit off because you’re body is still used to the oval ring. This can cause your performance to suffer temporarily until your body adapts. When you shift back, the same thing happens.
Oval Chainrings and Chain Length and Tension
One somewhat common question about installing oval chainrings is how do you adjust the chain length. After all, the chain tension changes as you ride due to the effective radius change caused by the elliptical ring.
The answer is that you simply install the chain the same way you install it with a round chainring. You will want to make sure that your derailleur isn’t stretched to its maximum when the chain tension is at its greatest. That happens when the long diameter sides of your oval chainring are at their furthest distance from the rear derailleur.
One interesting thing I learned while researching this article is that the difference in chain tension as the effective radius of the chainring changes is so minimal that you can even use oval chainrings on a fixed gear and single speed bike. You would think that the chain tension would change too much as your ride, but that’s not the case.
Buying an Oval Chainring
When choosing an oval chainring, the most important consideration is that it fits your crankset. Every manufacturer uses a different crankset mounting system. For example, Shimano cranksets require different chainrings than Sram. One brand may sell cranksets with different mounts as well. For example, Shimano uses different chainring mounts for their different groupset classes. You don’t want to have to buy an entirely new crankset just for a new chainring. Luckily, most oval chainring manufacturers sell multiple versions of their chainrings so they work with most cranksets on the market.
Once you find an oval chainring that is compatible with your crankset, you’ll need to decide on the number of teeth. Remember that more teeth give you higher gearing and fewer teeth give you lower gearing. If you’re pleased with the gearing of the round chainring that’s already on your bike, the easiest option is to buy an oval chainring with the same number of teeth.
A few popular oval chainring brands include AbsoluteBLACK, Wolf Tooth, Fifty Fifty, and SRAM.
Amazon has an excellent selection of oval chainrings here.
Final Thoughts about Oval Vs Round Chainrings
Oval chainrings are becoming increasingly popular among road and mountain bikers. They offer a number of benefits over round chainrings under certain circumstances. If you climb ride in a particularly hilly area or have a less than perfect pedal stroke, you are a good candidate to at least give oval chainrings a try. Generally, mountain bikers benefit more from switching to an oval chainring than road riders.
Having said this, some riders just don’t like oval chainrings for one reason or another. Maybe they experience knee pain. Maybe they just don’t like feel. To find out whether or not you like an oval chainring, you’ll just have to try one out.
Where do you stand on the oval vs round chainring debate? Share your experience in the comments below!
For more info on chainrings and putting a drivetrain together, check out my 1X Vs 2X gearing pros and cons list.