Coney,

Biopace chain rings are easier on the knees then round ones. The problem with them is that they are less efficient at a higher cadence.

In the last year I have owned 3 bikes, in this order: a comfort bike with round rings, an older road bike with biopace, and a road bike with round rings. I live in a hilly area, and the only bike that I could ride without getting any knee discomfort, was the bike with the Biopace rings (and this bike was geared very high compared to the others).

However, feel free to use any excuse necessary to get a new bike.