Figured I'd give one of these oval chainring setups a try. Its a shame that these never quite picked up on the market.
While the smaller chainring is more subtle, its effect becomes particularly noticeable when you shift to the larger chainring. It feels weird at first, but your body quickly adapts and learns how to make the most out of the change and crank rotation.
When pedaling on regular circular chainrings, you might find that the top half of the pedal stroke puts you into a more effective position to crank out some extra power versus going from the bottom half back up to the top. As such, the cranks actually move faster down than they do back up.
as such, the chainrings increase in diameter at the top half of the stroke, and then decrease at the bottom half. The end result is that power delivery is noticeable smoothed out - it is now one, smooth continuous movement, taking full advantage of the powerful part of the pedal stroke and "conserving" this energy in order to speed up the crank revolution through the less efficient area of the pedalling stroke.
While it is rather subtle in the smaller chainring like I said, in the larger one I feel noticeably more efficient and definetly a little bit faster. The sensation is almost as if the cranks are pedaling themselves when you are rolling on smooth pavement. Its a very natural feeling that's gentle on your knees and apparently helps to increase the blood flow in your legs. Im definetely quite happy with these compared to my original Sugino circular crankset.