For some the idea of oval chainrings is laughable, a relic fad from 1980s that is simply rebranded Biopace technology so that it can be marketed at the modern mountain biker. Modern oval rings from the likes of Rotor and Absolute Black use different shapes and orientations from the original Shimano offering. Shimano orientated the larger radius in line with the cranks reaching a 12 and 6 position with the thinking that this would smooth out a rider’s pedal stroke. While there were fans of the Biopace system, it proved unsuccessful with many riders noting an increase in knee pain.
Where modern oval chainrings differ is that they orientate the largest radius in the power zone of the rider’s pedal stroke, around the 3 and 9 positions, increasing leverage and reducing the effect of the ineffective dead zone to create a more optimized and smoother pedaling experience. While oval rings are not for everyone they are certainly worth trying out as they can offer some noticeable benefits when climbing or riding long distances to some riders.