While cycling in any guise is a great way to get out and explore the areas around you, I can’t think of a sport that comes with more opinions when it comes to components. Most of us agree that 26inch wheels are a dying breed; but what’s better 27.5 or 29? 180mm or 203mm rotors? Shimano or SRAM? Maxxis or Schwalbe? The list goes on.
However, nothing puts the cat amongst the pigeons quite like the oval chainring!
Although I wouldn’t force one on anyone else, I swear by the oval chainring and rarely ride a traditional round one. I’ll get to why this is later but first, what is an oval chainring and could it change your riding experience?
The science
If you want to know the scientific benefits of the oval chainring there is a plethora of research on the internet but here is the basic theory
In any machine-driven system as long as the power is even, and predictable round cogs are the way to go for maximum efficiency. However, the human body, while wonderful, doesn’t produce even or predictable power. Our legs are designed to go one in front of the other not round in circles. This means while pedalling we get weak or dead spots in the rotation; this is why professional cyclists spend their careers monitoring and perfecting their pedal stroke to the point any weak spots become marginal.
Unfortunately, for the majority of us amateur riders, we don’t have the time or training support to develop the perfect pedal dynamics, step in the oval chainring.
If you consider your cranks as a clock face, the points we produce most power or leverage are between 1 and 5 and 7 and 11. These are the points one of our legs is driving downwards. Through these 2 zones the chainring is at its widest to allow for maximum power.
Between 11 and 1 and 5 and 7 are the dead spots – the points our legs are coming back round and not creating power. The ring is narrower to reduce effort moving through these zones thus saving energy.
But how does this translate to your bike?
Well, if you take a 32 tooth round chainring and squash it into an oval it will get wider in 2 sections (Power Zone) and narrower in 2 (Recovery Zone). The Power Zones will become closer to the radius of a 34t ring while the smaller sections will be squashed closer to the radius of a 30t ring. For this reason, most manufacturers advise you drop one size chainring so you’re pushing the same size you’re used to but benefiting from the smaller recovery zones.
It should be noted that the chainring itself doesn’t produce more power but allows you to work a little less for the power available by conserving energy. The other huge benefit, and the reason I moved to oval rings is that it smooths out the rotational movement in our legs and hips by eliminating, or at least reducing the dead spot.
My thoughts
First of all, I’m not some crazy oval ring fanboy that pushes the oval chainring on everyone as some kind of miracle solution to all your cycling problems. It has however contributed to me still being able to ride a bike.
11 years ago I had surgery on my lower back partly due to sporting injuries and partly due to improper curvature in that area. I suffered painful sciatica limiting even the gentlest of wanders never mind a good bike ride. Surgery was a success for me, I have almost normal movement back, but I still suffered sciatica after any ride of more than around 5km. This would range from a day of pain through to a week of struggling to move.
I tried everything, different saddles, different bars and stems, pedals, cleat position, strengthening exercises and mobility. Nothing made any difference until reading an article about oval chainrings alleviating knee pain. The theory seemed logical even if the scientists can’t agree.
I’ve now ridden oval rings almost exclusively for 4 years. Yes, you can still run a clutch derailleur, any speed cassette and chain guide as with a round chainring. Yes, on the bike they look a bit odd, particularly looking down from a riding position and while I’d like to say I could, I wouldn’t put my house on being able to tell the difference in a blind test.
However, I have found that the rotation feels smoother and climbing is more easily sustained. If this is just a placebo then that’s fine with me!
The biggest success story has been the reduction of pain in my lower back and sciatica. As further support to this, I picked up a new bike last summer and rode (endured) the first 150km with the stock round chainring immediately flaring up that sciatica. It now has the appropriately sized oval bringing a return to pain free riding. That alone is enough for me to justify the steep price tag on some brands.
The oval chain ring won’t work for everyone but if you suffer back or knee pain or want to improve your endurance or pedal stroke it may well be worth the gamble and a proper test.
