Biopace was a sound design but a marketing fail for Shimano and now we have seen the return of non round chain rings at the professional level and this might trickle down for regular users.

This is what Shimano did not do with Biopace... most of their stuff starts at the top and trickles down and Biopace was sold at every level and think they had a very strong belief that this would revolutionize chain wheels and that everyone should have it.

It is a good system that works in a wide range of applications... it is great for climbing and at very high rpm can smooth out one's pedal stroke and they are not any harder on your knees than round chain rings and can actually help people with knee issues.

Their design unloads the pedal at it's highest stress / load point and allows you to maintain a consistent crank speed and I have more than a few clients who have had knee issues and surgeries who love their Biopace rings.

I blew out my knee 4 years ago on the trail and could ride a Biopace long before I could ride with a standard round chain wheel... it wad definitely easier on the knee.