Does anyone know about what is the deal with shimano biopace chain rings… I know the theory behind them but how do they feel? or how do they ride
any experiences?
it has been a few years, but as i recall the main feeling was of your leg dropping quickly thru the downstroke. interestingly, my knees would pop and crakle when first on them - not in a painful way but like popping your knuckles. you did not pedal them in the " push over the top and scrape backwards" fashion, or in circles - you just hammered on them. you could not feel it but you actually surged noticeably with each downstroke - this could be readilty observed by those around you on round rings.
taku, I knew you were a man of great intellect. I have a confession to make before all of society, and I hope this does not change your opinion of me. Please do not judge too harshly: I have used Biopace chainrings. I did so willfully but with a certain amount of “shame”. I feel so dirty ever since, but now I feel absolved of all my guilt and shame, before the hallowed tribunal of Slowtwitch. I know others will cast aspirtions upon me, but i can hold my head high knowing I had the strength to come clean. Using Biopace chainrings (I only did it once). Does not make me any less of a person… blah, blah, blah… I used a Biopace HP (high perfromance, a less eccentric version of the standard Biopace)at Ironman Canada '97. My theory was it would help me get over Ricther Pass and Yellow Lake easier. I am sure to some degree it had an effect. I’m not sure if it helped. It does change the feel of your pedal stroke. “Real” cyclists (read: snobs) pooh-poohed the idea of Biopace and it went away some time ago. An interesting incident in the Tour de France involved a team, Systeme U, who debuted an eccentric chainring that was promptly banned by the UCI. Biopace may have worked, I don’t know. I still have my trusted 39 tooth Biopace HP chainring, and I am not ashamed of it. I do ride round rings now though.
I rode 40 bipaced miles today. I think they work good till you get to higher cadance then they feel choppy. I like the controversy of the crank. The emotion that comes out . It’s amazing how worked up we get. So for all these reasons I will keep mine.
Thanks Dirtball!
dirtball. do you have a stash of them hoarded away or something ?? now THAT would be cool, in a sick sorta way. 
Sheldon “Better Than Round” Brown has an interesting writeup on his site…
I used to ride with a guy who had a 1 inch plus leg length discrepency due to an accident, which also caused some strength issues. He designed his own elliptical chainring to use with a custom made cleat spacer. I say this because he is the only person I have ever met who was happy using any type of elliptical chainring and he really had no choice. Except for special needs such as this, I would avoid them IMHO.
One of the guys who did my original beta testing on the PC’s had biopace on his bike and put them on the PC’s. He could not tell any difference even though he had no idea how the oval was aligned to the cranks. I think this “advantage” or “difference” is so small as to be imperceptible to the typical user.
Frank
The UCI BANNED the eccentric chainring? And have allowed Rotor Cranks? Just shows that many of these equipment rules are completely arbitrary.
Frank