Asymmetric chainrings are still something I get asked about by athletes hoping to improve their cycling performance.
The popularity of these oval chainrings has waxed and waned since Shimano’s introduction of the Biopace system in the 1980s. Interest peaked a decade ago after Carlos Sastre, Bradley Wiggins, and Chris Froome each won the Tour de France using these curious non-round chainrings.
The idea behind asymmetric chainrings is simple. Cyclists produce varying amounts of power at different points of the pedal stroke, usually peaking when riders push down on the pedals and fading away as the rider pulls the pedal back up to the top.
Asymmetric chainrings change the gear ratio through these different phases, effectively giving the rider a larger gear as they push down on the pedals and a lighter gear through the low-power phase near the top of the pedal stroke.
In theory, this makes sense, but is there enough evidence to support the use of these novel chainrings?
There has been a reasonable amount of research into asymmetric chainrings. So, what does the literature say?
The Evidence
Despite there being quite a few published research studies looking into the potential performance benefits of asymmetric chainrings, what becomes glaringly apparent when looking through the papers is that nearly every study comes to the same conclusion; that is, there is no compelling evidence that asymmetric chainring designs are going to help you ride faster. In fact, in the studies that have been run, asymmetric chainrings don’t appear to make much difference at all.
This might help explain why when I visited the Rotor Bike website (currently the largest producer of asymmetric chainrings), I couldn’t find links to any studies that back up the company’s claims of improved pedalling efficiency. This is telling because, at the very least, I was expecting to find one or two cherry-picked studies that showed some benefit, but that wasn’t to be.
There were plenty of positive claims in Rotor’s advertising material but no sign of any evidence, strong or weak, that backed up the claims.
In science, we must consider the entirety of the available evidence instead of cherry-picking single studies.
I genuinely wanted to find evidence indicating these chainrings would make me faster, but the best I could find was one study that looked at BMX sprint starts.
This study, published in the Journal of Science & Medicine, looked at the first few seconds of a BMX race start. The researchers found that riders performed better using an oval sprocket than the traditional round one.
My takeaway from this BMX study is that perhaps someone needs to study other events that require maximal exertion out of the starting gates, such as team and individual pursuits on the track, to see if faster starts could lead to improved overall times.
Some studies also show slight variations in leg stability and neuromuscular control when using asymmetric chainrings. Still, the overwhelming amount of published research concludes that asymmetric chainrings won’t make you ride any faster…or slower.
The main reason for this may be that the low-power dead spot these chainrings are purported to help eliminate is ultimately an insignificant part of a rider’s pedal stroke.
So, even if the gear ratio is lighter as your foot travels through this point, the power output that your legs produce is still insignificant. Riding a smaller gear doesn’t make riders produce more power through these dead spots in the pedal stroke.
In Practice
I’ve worked with several clients over the years using asymmetric chainrings.
Some riders claim that they feel much more powerful and perform better times.
For these clients, I’m happy for them to reap the benefits regardless of what drives any performance improvement.
The evidence shows that it may be due to something as simple as the placebo effect. Tell a rider that a product is more efficient, and they’ll most likely ride faster.
From a bike fitter’s perspective, the only other thing I have noted with these non-standard chainrings is that riders sometimes find the gear shifting less reliable than standard chainrings. I don’t know if this is a universal issue. Still, it is worth consideration for racers who demand reliable gear shifting under high power loads.
So sadly, despite my hope that Q-Rings could be a secret weapon to improve cycling performance, when the evidence is weighed, we can conclude that it is doubtful that asymmetric chainrings will significantly improve cycling performance.
With this in mind, they are also unlikely to hinder your performance, so feel free to continue using them if you wish.