I don't get too worked up about BioPace but it bears mentioning that they worked nearly backwards to the Bullseye and other previous non-round rings dating back to the 19th century.
Those older designs worked as Jim said, increasing your gear during the peak power zone. Biopace decreased the gear in the power zone, which made the rotation accelerate; the idea was the higher gear in the "dead spot" would capture the momentum of the leg at the bottom of the stroke, momentum otherwise lost with normal rings (sez Shimano).
Note, I don't believe that good cyclists lose energy this way, but it could be that inexperienced cyclists are more efficient with Biopace.
As to the relative timing of Biopace and Suntour OvalTech: at the shop I worked in, Ovaltech came in later. I always assumed it was a Biopace knockoff. Anyone have any corroborating evidence? Anyone care? ;^)
Mark Bulgier
> -----Original Message-----
> From: Diane Feldman [mailto:feldmanbike@home.com]
> Sent: Wednesday, January 31, 2001 8:32 AM
> To: Jim Foreman; Rick Miller
> Cc: [unknown]
> Subject: Re: [CR]chainrings
>
>
> Durham, aka Bullseye, went to a more drastic extreme with
> this idea a few
> years before Biopace. I forget the product name but their
> chainring was too
> ovalled to use as part of a multiple chainring system, was
> made in a range
> that STARTED at about 54 teeth. I rode the Davis Double one
> year in the
> mid-70's in a group with a guy who was completely sold on these
> football-like rings; as the day wore on he was more and more
> envious of the
> rest of us in the group, looking longingly at our 42/24 low gears!
> David Feldman
> ----- Original Message -----
> From: "Jim Foreman" <JIMFORE@compuserve.com>
> To: "Rick Miller" <millere@telenet.net>
> Cc: "[unknown]" <classicrendezvous@bikelist.org>
> Sent: Wednesday, January 31, 2001 7:54 AM
> Subject: [CR]chainrings
>
>
> > Message text written by "Rick Miller"
> > >I have an early 80's touring bike equipped with Shimano
> Bio-Pace rings.
> > I've rarely seen them used and wonder what their purpose
> was? I suppose it
> > should be obvious but I prefer the round rings.<
> >
> > Bio-Pace rings were just another one of Shimano's
> me-too deals. A
> > couple years before it was SunTour with their OvalTech
> rings. SunTour
> found
> > out just how unpopular they were and dumped them about the
> time Bio-Pace
> > came out. Shimano stuck with them for several years.
> > The idea is that the ring has a longer radius like
> a bigger ring
> > where the most power is exerted on the pedals is the
> greatest and the
> > shortest where you can apply the least power.
> > I agree, they are a bad idea and like most everyone
> else, went to
> > round rings as soon as possible.
> >
> > Jim
> >
> > http://www.geocities.com/