We know, there’s no such thing as a stupid question. But there are some questions you might not want to ask your local shop or riding buddies. AASQ is our weekly series where we get to the bottom of your questions – serious or otherwise. Hit the link at the bottom of the post to submit your own question!
Maybe you’ve heard of oval chainrings but you’re not entirely sure what all the fuss is about. A good number of brands now offer ovals and we’ve seen uptake across disciplines, from Pro Tour road cycling to the upper echelons of the Enduro World Series. Oval chainrings essentially require less effort to drive than traditional round ones, tempting us with prospects of marginal gains. But why is this? And how ‘oval’ does it need to be? And what size oval should you get if you make the change? All of these questions and more are answered below by the industry experts absoluteBLACK, ROTOR Bike and Wolf Tooth Components.
Why is it less effort to drive an oval chainring compared to a round one?
ONEUP COMPONENTS: It isn’t. Sorry to disappoint. There are lots of biomechanics studies investigating the benefits of oval and other non-circular chainrings for road biking. Almost all of them focus on power gains. The reality is that the power advantages of oval rings are so minute that they can only be measured with elite level professional athletes on a turbo trainer or test track.
For mountain biking the real benefit is increased climbing traction. To paint a picture of the usage, most mountain bikes do not have a low enough gear to be able to ‘spin’ up steep loose grades. The pedaling motion therefore becomes very biased to powerful, sometimes out-of-saddle, downward thrusts. A portion of the momentum is used to help carry the pedals over TDC and the cycle starts again. The oval ring therefore ‘smooths’ the torque delivered to the ground and allows the rider to maintain traction. Increased traction means less wasted energy used to throw rocks at your riding buddies.
Regarding power meters it is important to account for the bloated numbers that you’ll see when using an event-based system (most crank/pedal/chainring power meters).
ROTOR: The oval (as positioned by Rotor’s Optimal Chainring Position) reduces the amount of effort required in the weak (back) part of the pedal stroke, and allows the rider to maximize the stronger part of the pedal stroke.
absoluteBLACK: The human body uses skeletal muscles to generate force on the pedals, predominantly during the downstroke. Each skeletal muscle has a unique characteristic that doesn’t allow even muscular force throughout its contraction. For example, peak joint power from the knee occurs at around 70 degrees crank angle (0 is at 12 o’clock), whilst the hip peaks well beyond 90 degrees crank angle. Further adding ankle joint power, angular velocity of the crank, inertia of the leg and the force effectiveness, which is how much of the force generated of the muscles is actually transferred to power, we can see that a power profile throughout a crank cycle is not even, but peaks somewhere around 110 degrees of crank cycle (normal road cycling, for example). AbsoluteBLACK oval chainrings are designed to perfectly fit a specific riding style and involve the hip joint to a larger extent, which essentially takes the load off the knee and adds to muscular efficiency. AbsoluteBLACK oval chainrings’ major axis orientation, that is when the chainring’s diameter is the largest, matches the power profile of a cyclist to reduce power losses and transfers the load from the knee to the hip. This was established based on several thousand measurements using one of a kind diagnostic equipment to measure 3D pedal forces and joint loading. Measurements were carried out on thousands of recreational road & mtb riders and hundreds of professional riders, including the entire Pro Tour Team UAE where we officially deliver our scientific biomechanical optimization services with our Science Lab. With such a wealth of data we are able to precisely design the chainrings that are able to increase the mechanical effectiveness – which means you perceive it as having less effort going at the same speed compared to round.
Wolf Tooth Components: Short answer: Oval chainrings synchronize pedaling with the biomechanics of the human body. These chainrings provide lower gearing in crank arm positions where you can’t generate as much power and higher gearing in positions where you can generate more power.
Longer answer: Wolf Tooth elliptical chainrings are designed to synchronize pedaling with the biomechanics of the human body and the geometry of crank arms. When the crank arms are near vertical you have less leverage and you are using smaller muscles to apply power to the crank arm. To compensate for that, we designed the chainring to effectively be two-teeth smaller in these orientations where you can’t generate as much power. Conversely, when the crank arms are near horizontal you have much more leverage and you can take full advantage of your quads to apply much more power to the crank arm. To compensate for that we designed the chainring to effectively be two-teeth bigger in these orientations where you can generate more power. So if you have a 32 tooth elliptical chainring it will feel like a 30 tooth chainring when your cranks are near vertical and a 34 tooth chainring when your cranks are near horizontal.
Will my chain have a greater tendency to drop if I use an oval chainring?
ONEUP COMPONENTS: No. We use the same tooth profile on our oval and round rings. Both offer extremely effective chain retention. Our new 12 speed Shimano HG+ rings are available now.
ROTOR: Shift performance can be impacted depending on specific drivetrain, front derailleur setup, frame geometry, and other factors. Mechanics experienced with ovals can diminish any negative inclination toward dropped chains, however.
absoluteBLACK: No. If we compare an aB round to oval narrow-wide ring there is absolutely no difference in the chain retention capabilities. But there is a difference among brands (regardless of the chainring shape). This is because every brand has designed the teeth differently and they will behave in a different way when they wear out a little or you use them in the mud.
Wolf Tooth Components: No. Chain retention has nothing to do with chainring shape. Chain retention is all about making sure the chain stays aligned to the chainring while you are pedaling. This is accomplished by designing chainring teeth to self-align to the chain, minimizing how much the chain bounces (i.e. clutched rear derailleurs), or with mechanical chainguides to force alignment. (On a wide/narrow chainring, every tooth on the chainring aligns the chain with the chainring which makes them significantly better than non-wide/narrow chainrings where the chain is only guided by the narrow links in the chain).
Are there any chain devices specific to oval chainrings?
ONEUP COMPONENTS: Yes, OneUp was the first company to design a chainguide specifically around an oval chainring. These were designed concurrently and launched in 2015. The OneUp V2 Chain guide allows for more extreme ovalities and simplifies height adjustment.
Wolf Tooth Components: Yes, certain chainguides like the Wolf Tooth GnarWolf are designed specifically to have enough overlap to ensure the chain properly meshes with the chainring at both the largest and smallest diameters of and oval chainring.
absoluteBLACK: Yes. absoluteBLACK offers a full range to fit all major frame mounting systems. The difference is mainly in the cage itself. It has to be taller and profiled differently to be able to cope with variable shape of the chainring.
Can I increase the size of the chainring I run if I use an oval one?
ONEUP COMPONENTS: No. Oval rings do not give the rider superpowers (or any extra power for that matter). As such, we recommend sticking with the same size.
ROTOR: You can do anything you want! However, we recommend people stay with their original ring size, since using a Qring is about reducing the dead spot in the rider’s pedal stroke. Some riders do find that they are comfortable pushing a bigger gear with the diminishing of time spent at the back of the pedals stroke, but that’s individual preference.
absoluteBLACK: Yes and no. We always recommend swapping like for like, so if you have a 32T round ring at the moment, you should consider getting a 32T oval. The same applies to our shiftable road oval chainrings. This recommendation is based of course on the assumption that the current round chainring is of the right size for your riding style and abilities. If you feel currently that your round chainring is too big or too small then reduce/increase the size of an oval in the same way as you would with the round ring.
Wolf Tooth Components: It depends. One pedal revolution with a 32T round chainring will get you exactly the same distance as one pedal revolution of with a 32T elliptical chainring, so if you pick your chainring size to make sure you never spin out in your biggest gear, we generally recommend using the same size chainring for both round or oval. However, since many people select their chainring size to be small enough to provide the low gearing they need to get up the steepest climb they encounter on their ride (and that is ultimately determined by having enough power to make it through the weakest part of their pedal stroke) many people are comfortable using a oval chainring that is two-teeth bigger than the size they would pick if they were using a round ring.
Will my chain wear faster or slower with an oval chainring?
ONEUP COMPONENTS: No. Oval rings do not contribute to additional wear. Though it should be noted that at extreme chain angles as viewed from the drive-side of the bike, (ie. The angle between the upper and lower chain lengths like when pedalling in the largest cassette cog), the rear derailleur cage will move thereby adding wear to the derailleur clutch. This is relatively minor compared with the amount of normal clutch movement.
ROTOR: Should be exactly the same. It’s the same gear inches.
absoluteBLACK: Our oval chainrings are designed in a way that they always pull the same amount of chain at any position of the crank rotation. Imagine an ellipse which you can cut through the center at any place and it will always produce equal halves. The same is true for the circle. Because of this, chain wears in the same way as with the round chainring. It goes without saying that the best way to increase the life of any chain-chainring combination is to lube the chain regularly and keep it clean.
Wolf Tooth Components: No. Chain wear is determined mainly by factors like how well your chain is lubricated, how much dirt and grit gets on your chain, how much power to apply, and how much time is spent in cross chained gears. If anything, elliptical evens out the variation in power that gets applied to the chain during a pedal revolution so there is less cyclical loading of the chain which could actually extend the life a tiny amount.
How ovalized does the chainring need to be, in order to be effective?
ONEUP COMPONENTS: The effect is proportional traction-wise but in our testing, we found other constraints limit the ovality. We choose 12% and 115° clocking and detune that to 10.5% on the 34T and 36T for better MTB chainstay clearance. When you get as high as 14% or 15% riders started commenting that out of saddle efforts felt inconsistent especially when navigating downhill trail features.
ROTOR: ROTOR has made rings varying in ovality from 10% to 16%. After extensive testing, we adjusted all rings to 12.5% ovality for best rider biomechanics.
absoluteBLACK: This is an interesting question without a definite answer. Our testing, that I mentioned above, revealed that somewhere between 8% and 14% yields an optimal result. But it very much depends upon the riding profile (e.g. road vs. MTB), chainring size, cadence and many other factors. We have optimized every chainring size and type to achieve the best possible result.
Our collected data on thousands of riders clearly show riders behave differently using different chainring sizes and riding different types of bike. To give you an idea, there is a very strong reason why someone is using a 36T chainring where someone else, in the same terrain, would use a 28T. Are these two hypothetical riders of the same level of fitness? Would they have the same power output, cadence, lactate threshold, body type or oxygen consumption?
But this is only part of the picture. The most important aspect in the oval chainring design is not only the ovality, but also the actual chainring shape and timing of the biggest radius of the chainring vs the crank arm. We optimize all of this per chainring size and type. Only then can we ensure a smoother and more effective pedal stroke that we are able to prove scientifically.
Wolf Tooth Components: There are lots of varying opinions on this and it probably varies a bit from person to person depending on bike and body geometry. Wolf Tooth chose 10% ovality to provide a meaningful amount of biomechanical benefit without being so extreme that it feels like you are pedaling squares.
How does an oval chainring effect the anti-squat of a full suspension mountain bike?
ONEUP COMPONENTS: The change is negligible. In the power stroke you have a larger diameter but also lower chain force. It is more notable that you’ve smoothed out your pedal stroke so should be feeling less bob.
ROTOR: The oval adds leverage to the rear dropout, depending on the chain’s placement in the gearstack. On anti-squat systems such as DW, the oval could feasibly add to the anti-squat platform. This would be notably untrue on a high-pivot or idler system, as they would negate the added extra torque, driving the wheel into the ground, potential for the oval.
absoluteBLACK: Excellent question. With a properly designed oval chainring you are achieving a smoother pedal stroke. That means you smoothen out the peak forces when you pedal. It can be nicely observed when going uphill. You would notice much better rear wheel traction on loose terrain. This effect also translates to much smaller pedal bob during riding, which properly designed anti squat is aiming to remove. Therefore simply going oval reduces the pedal bob and improves your effectiveness regardless of the frame construction.
Wolf Tooth Components: Anti-squat varies while pedaling with an oval ring, compared to the constant anti-squat found with a round chainring. You’ll find a much stronger fluctuation in anti-squat based on what cassette cog the chain is in than you would with an oval chainring. With everything else happening on a full-sus bike as you ride, this isn’t likely noticeable.
Will an oval chainring change the amount of pedal kick back experienced by a rider when descending on a full suspension mountain bike?
ONEUP COMPONENTS: Again, the effect is pretty negligible
ROTOR: Not really, because the pedal kickback is related to the squat system, and when descending, the rider is generally not engaging the drivetrain, which is where the oval can be beneficial.
absoluteBLACK: No. This only depends on the size of the chainring and frame construction since the chainring is not in motion.
Wolf Tooth Components: Pedal kick back varies while pedaling with an oval ring, compared to the constant pedal kickback found with a round chainring. With everything else happening on a full-sus bike as you ride, this isn’t likely noticeable.
Thank you to Borut Fonda, lead Scientist at the absoluteBLACK Lab, Lori Barrett at ROTOR, Kurt Stafki at Wolf Tooth Components, and Jon Staples at OneUp for contributing to this week’s AASQ. Got a question of your own? Click here to use the AASQ form to submit questions on any cycling-related topic of your choice, and we’ll get the experts to answer them for you!