Latest Info On Non-Circular Chainrings?

Triathlon Forum
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A few years ago there was allot of contention on if non-circular chainrings actually did anything. It seemed that things were pretty unclear.

Now that it’s a few years later, I was wondering if new studies have shed any additional light on this topic?

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Which new studies?

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I was wondering if there were any new studies that provided enough evidence for or against them to settle the argument
.

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As far as I know, there aren’t any new studies.

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There are always new studies. I’ve not conducted any, but my review is that most studies are inconclusive for various reasons. Results tend to range from statistically insignificant, to favorable maximal power output for oval rings by up to approximately 6%. I’ve yet to see a claim that non-round rings are detrimental to performance.

From a mathematical perspective, it is simply not possible for circular rings to optimally load leg muscles under maximal power, if by optimal we mean that the required power for each muscle group is proportional to their relative capacities.

From a practical perspective, the deviation from circular that may be required to achieve various “optimal” load demands as a function of crank angle may exceed that which allows for shifting without issues under racing demands.

Under sub-maximal efforts, cyclists provide their own “weighting function” by simply employing each muscle group in proportion to their desires and abilities. One can observe this in any pedaling power output scan, which tends to show a “peanut” shaped distribution with crank revolution. I believe this self-selected muscular loading is what clouds many studies.

Intuitively, consider measuring the maximum torque you can apply with cranks at 12 and 6 o’clock at a stand-still, with the rear wheel locked in place. Then try the same with pedals at 9 and 3 o’clock. This represents the maximum torque one can possibly provide to the pedals at each position, since allowing any rotation of the crank reduces the resistance. Approaching extremely high cadences, pedaling torque is significantly reduced (see studies on BMX racers). At low-momentum efforts, one is less able to self-select muscle loading, as there will be minimum torque required for a given crank angle at X rpm and Y power, which is likely to hurt more at the top of the stroke than the downstroke, hence people “pedaling squares” up steep slopes.

I’ve played around with crank angle on my oval rings and definitely have a preferred angle of +5 degrees. Under maximal efforts I also prefer the pedaling torque distribution of an oval 53 chainring which peaks at equivalent to 56 but is only 50 near the top of the stroke. When cruising at something like 70% FTP or below, I don’t think the difference is noticeable.

I have not tried QXL or Ossymetric rings, but I’d consider them for time trials, and probably not for conditions where I’d want fast reliable shifting.

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// study n=1 2500h … it depends on how a rider can work with the oscillating inertia of the chosen oval …

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I started using using Rotor QXL rings a few years ago and swear by them (and I don’t have any issues shifting). They are on all my bikes and the difference for me was immediate. Its probably like many things triathlon, it really depends and the only way to know if they work for you is to try them for some time. I swear by them but you will find lots of other people who say they didn’t feel any difference using them.

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The studies show that you should try them and keep them if you like them. Get rid of them if you don’t.

There’s no magic amount of watts that get attributed or a more efficient pedal stroke for 100% of the population.

It just comes down to personal preference. I personally didn’t notice much of a difference and have gone back to round ones

9

A few years ago there was allot of contention on if non-circular chainrings actually did anything. It seemed that things were pretty unclear.

Now that it’s a few years later, I was wondering if new studies have shed any additional light on this topic?

I haven’t seen anything since this summary that would change the conclusions:
https://trstriathlon.com/elliptical-chain-rings-dont-work-because-you-wont-let-them/

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If you understand how elliptical chainrings are supposed to work (assuming that they work as claimed regarding improving biomechanical effectiveness or efficiency), I can say something of which I am 100% sure.

And that is, that unless you have fully custom rings made for your exact set up and position, you MUST use adjustable (angle adjustable) elliptical chainrings if you have any hope of utilizing their benefits.

11

It’s worth checking how any study measures the rings proposed benefits. It’s well known now that several studies are in fact flawed since the oval ring affects the foot speed and over-inflates the power reading as a result if you’re using a crank-based power meter.

12

I have an absolute black 50t chainring on my Dura Ace crank.
I can say with 100% certainty, that I like the way it looks. :slight_smile: (and no issues with shifting).

13

If you understand how elliptical chainrings are supposed to work (assuming that they work as claimed regarding improving biomechanical effectiveness or efficiency), I can say something of which I am 100% sure.

And that is, that unless you have fully custom rings made for your exact set up and position, you MUST use adjustable (angle adjustable) elliptical chainrings if you have any hope of utilizing their benefits.

Rotor Q rings are adjustable on their cranksets.

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If you understand how elliptical chainrings are supposed to work (assuming that they work as claimed regarding improving biomechanical effectiveness or efficiency), I can say something of which I am 100% sure.

And that is, that unless you have fully custom rings made for your exact set up and position, you MUST use adjustable (angle adjustable) elliptical chainrings if you have any hope of utilizing their benefits.

Rotor Q rings are adjustable on their cranksets.

Yes, I know.
But many (all?) of the other brands of non circular rings are not.

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Now that Rotor has their direct-mount adjustable system, you can adjust the angle on any brand of chainring that fits the 4 bolt Shimano pattern.

16

No new studies are as I know of, by that I mean ‘independ’ studies.

That said, out of pure curiousity I tried the controltech eccentric chainrings.
And that is something completely different.
And I’ve ridden Q-rings, QXL, Osymetric and Absolute Black.
I like them all in a sort of way, but never, never will say that I ride faster or higher power with them
Well, higher power you get, but that’s because they are not round, you don’t actually ‘get’ more power or speed at the same effort.

But then the controltech eccentric rings…this year I have not been my shape and form of 2019, but with those rings I rode on every distance a PB.
There is out and back course I ride a lot, so lot’s of material to compare.
It’s 52 km, and with the eccentric rings I’m always about 2 min faster on almost every ride since I placed those rings.

They were a bit weird at first, as if you were riding ‘limped’ on the left side but that went away after a few weeks.
I never had to get used to oval, but these rings were really different.

What I found with these rings I can push a heavier gear then with other combo’
And for longer durations.

Jeroen

17

Just to add another bit of colour into the thread - we (AeroCoach) make noncircular 1x and 2x chainrings for TT and road called ARC rings, and I designed the shapes based on a whole heap of pedal mechanics data during my academic career.

The things to note with the ARC rings are that the shape is very subtle, it changes depending on the size of the chainring, and also the shape is not an oval. I’ll run through why that’s the case along with some general notes:

  1. First thing to note is that you’re not going to get a 10w improvement (or even close to it) with a non round chainring. If you see that from the get go it is quite likely to be a power inflation from a very noncircular ring (the more noncircular the more the chance of power inflation with a power meter).
  2. Secondly, a shape that is very different from round is going to take some adaptation, which then over time affects your pedal stroke as you become accustomed to it. My recommendation if you like noncircular rings that have quite a dramatic shape is just to use them for racing but don’t train on them.
  3. Our rings change shape only very slightly, which has the side benefit of allowing you to race and train on them and swap between ARC and round without an adaptation period.
  4. Crucially, we change the shape of the ring based on the inertia you’re likely to experience because your pedalling mechanics change with inertia - at high inertia (big chainrings/high speed) the maximum effective gearing is only 0.5t larger than the average as your pedal stroke is more consistent (=less “choppy”). So a 60t ring goes up to 60.5t max (and 59t at minimum). With our smaller rings the difference is greater, as you’re more likely to be riding at slower speed with a 40t or 44t inner where your pedal speed changes more during one revolution. You’ll notice going uphill at slower speeds how it’s a more choppy pedal stroke, perhaps with the occasional clunk as you lose engagement in the freehub whilst moving through the top of the pedal stroke, that kind of thing.
  5. Because everyone is different, and because during the pedal stroke you hold peak force for a while rather than hitting it and immediately decreasing, we also hold the peak gearing period on the chainring over a longer phase than an oval ring (which hits peak and then immediately drops off the gearing), so that we ensure we can “capture” that peak regardless of your pedalling mechanics, as well as maintaining that peak gearing for as long as you’re applying peak force.
  6. On an ARC ring there are 8 different changes in gearing within one revolution, with a steep increase in gearing in advance of the power phase to mimic the sharp increase in muscular activity of the vastus lateralis, medialis and to a lesser extent tibialis anterior. After the peak gearing phase there is a smoother dropoff as the gastrocnemius and soleus (and again for some people tibialis anterior) come into play and bring your leg through the lower dead spot.
  7. Anecdotally our customer feedback is that the feel of an ARC ring is a bit like a flywheel once you get it up to speed, but again it is quite subtle (and you want it to be subtle).

So really it’s not a magic bullet, but certainly something that customers like for for sustained aerobic efforts as the ARC ring gearing is matched to how your muscles are firing. They’re also made from carbon which results in a bit lower friction and looks awesome.

18

54/40 the smallest option? Seems like you make these for time trialers and not triathletes!

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Larger rings are more efficient and we’ve always tried to push people in that direction - certainly with the advent of wide range cassettes and the ability for road rear mechs to take up 34t sprockets it’s okay to go big on the front without being limited by gearing. Can seem like a big step up but 4t on the front is roughly 1t on the back so not so bad if you think about it like that!

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Congrats on the AeroCoach UK partnership with Team Qhubeka Assos !!