Going g round d in ovals
The latest generation of non-round chainrings are the most refined crop yet
It was Shimano that popularised the concept of non-round chainrings back in the 1980s with its Biopace chainsets, but patents have existed for similar designs since 1894. There’s a very good reason why.
‘It’s a well-documented fact that humans are unable to exert even force on the pedals throughout the pedal stroke, resulting in relatively poor pedalling effectiveness,’ says Marcin Golec, founder of Absoluteblack. ‘This simple fact has inspired many inventors for more than a century in their efforts to optimise that force delivery during the pedal stroke.’
Shimano’s Biopace rings used a curious shape officially described as a ‘point symmetric egg curve’.
‘The shape delivered weird pedalling motion, and for some users even knee pain,’ says Golec. ‘The non-round concept has always showed promise but its development was hindered by a lack of adequate measuring equipment, and therefore data.’
Those knowledge gaps have since been closed, a process that has resulted in designs featuring more subtle oval or elliptical shapes.
Pablo Carrasco, co-founder of
Rotor, which makes Q rings, says, ‘An oval chainring works like an automatic shifting system. It gives you different effective chainring sizes within each pedal revolution. That in turn adapts the leverage of your crankset to the potential of the rider’s legs at each pedal position.’
Put simply, when correctly orientated an ovalised chainring effectively works with the biomechanics of the rider’s legs to provide a smaller gear when they’re at their weakest position and a bigger gear when they’re at their strongest. That gives rise to a host of claimed performance benefits.
‘The shape improves pedalling effectiveness and metabolic efficiency when compared to a round chainring,’ says Golec. ‘In simple terms, this means you will waste less force that does not contribute to moving the crank around, allowing you to achieve the same speed with less effort versus a round chainring. We’ve demonstrated that cyclists can exhibit a 9% more effective pedal stroke by applying less force to the pedals in positions that don’t contribute to power.’
An ovalised chainring works with the biomechanics of the legs to provide a smaller gear when they’re at their weakest position and a bigger gear when they’re at their strongest
‘The Osymetric shape gets the rider through their pedal stroke “dead-spot” 10% faster,’ claims company founder Jean-louis Talo
Rotor’s Q rings have what the brand dubs an OCP (optimum chainring position) feature, which allows riders to adjust the orientation of the chainring relative to the cranks depending on where the rings are determined to best suit the individual’s pedal stroke.
‘This ensures a rider’s peak power phase perfectly matches the biggest part of the ring,’ says Carrasco.
Suitable for all surfaces
Ovalised rings have a use beyond the tarmac too. Rotor says that because the shape improves pedalling efficiency, power delivery to the rear wheel is smoother, which increases traction in wet, muddy conditions. Indeed, the chainring shape is just as often seen on mountain bikes as road bikes.
‘Caveats do exist for the technology though,’ says Carrasco. ‘The oval shape doesn’t work with fixed gear bikes and very high cadences do tend to negate the provided benefits.’
And while the non-round designs have trended towards subtler shapes in recent times ( if not subtler finishes: Absoluteblack’s machined aluminium offerings are both intricate and eyecatching), that isn’t the case across the board. Osymetric’s ‘twin-cam’ shape is particularly radical. Founder JeanLouis Talo says this is to maximise the biomechanical advantages of a non-round design.
‘The Osymetric shape gets the rider through their pedal stroke “dead-spot” 10% faster than normal,’ he claims. ‘As a result the rider can experience lower lactic acid generation, so can produce more power.’
It’s a bold statement, but giving it credence are the results of Osymetric’s most famous users, Bradley Wiggins and Chris Froome.
‘Between them, they have used Osymetric rings to win five Tours, two Giros and one Vuelta,’ says Talo.
Independent research remains far from unequivocal as to the benefits of non-round designs, though, and anecdotal reports suggest front shift quality has been impacted in the past.
‘Some products may still have the problem today, but it mainly depends on the design of the shifting ramps and their timing,’ says Absoluteblack’s Golec. ‘We have found that regular pins used for lifting the chain are not particularly suited for ovals, so we have developed a radically different ramp design that shifts on a par with what Shimano Dura-ace users are accustomed to.’
So with the technology at its most accomplished right now, it may be worth considering trying out non-round rings for yourself. You might find you get on with them, you might not, but at least your opinions of what works best for you will be well- rounded.