So will we see the return of the Shimano Biopace elliptical rings? I've still got them on an old Marin Palisades, but I've never been convinced they're any better than round rings.

I also had Biospace on my old mountain bike. Why did Shimano stop it?

Surely these are nothing new? About 14 years ago when I was nowt but a nipper I worked in a bike hire place and out fleet of (far from top end) bikes had elliptical chain rings on them. Then the idea just seemed to go away. Has there been some new research to suggest that they're a good idea after all?

I too had Biopace rings on my '91 Marin Palisades Trail...ahh those were the days. I quite liked them but don't they create issues with front derailleur adjustment or sizing due to the rise and fall of the chain?

Dear Mr Huang,

Please find below in this e-mail a website address giving access to a recently published scientific study "Comparative biomechanical study of circular and non-circular chainrings for endurance cycling at constant speed".

Further on the same website you will find the test results of a first "R & D" project (Rotor System Crank), a project carried out by means of the mathematical model developed in the "paper".

The scientific study has been elaborated by three engineers, master of science degree, passionated by high tech cycling, specialists in (bio-)mechanics/dynamics and applied mathematics.

The authors do have a very thorough knowledge of the scientific publications in this field, do have an intimate knowledge of the design and manufacturing technology of gear wheels (chainrings...), do have regular contacts with authorities in the field of biomechanics such as prof M.L. Hull, university of California, Davis, USA, prof J. Rasmussen, university of Aalborg, Denmark (see www.anybody.auc.dk and www.anybodytech.com ) and prof S. Ratel, université Blaise Pascal, Clermont-Ferrand, France, and also with manufacturers/inventors of non-circular chainrings such as P. Carrasco (Rotorbike), B. Rosset (Ogival), J.L. Talo & M. Sassi (Osymetric) etc....

The aim of the authors was to search for a well-founded answer on the question: "Are non-circular chainrings superior to circular chainrings? If yes: why?"

By means of a mathematical model, eight non-circular chainrings are compared with a circular chainring, being the reference basis and this according to two criteria.

The test results of the study also allow to make a ranking of the investigated non-circular chainrings and last but not least the results lead to some very interesting general conclusions about non-circulars.

The results and the conclusions of the scientific study match "external results", so far of course these "external results" are available. This is giving confidence that the biomechanical model "reflects reality".

Some examples:

1. The model reveals and confirms what the riders already concluded in the past: Biopace is a totally wrong concept. Shimano has withdrawn its "invention" from the market in 1992.

2.The model confirms that mathematical correct elliptical chainrings with crank arm perpendicular on the major axis "behave" roughly as circular chainrings.

This was also the conclusion of professor M.L. Hull as described in his paper: "Physiological response to cycling with both circular and non-circular chainrings". Medicine and Science in Sports and Exercise 24/ 1114-1122, 1992.

Prof M.L. Hull tested, with a team of eleven trained riders, the non-circular Biopace, the ellipse Eng90 (crank perpendicular on vertical major axis), the ellipse Eng10 (angle of 10° with vertical major axis, clockwise, "Biopace-like orientation") and a circular chainring. "None of the measured parameters of the non-circulars showed significant differences with the circular one".

3.The model confirms the performance potentialities of the Osymetric-Harmonic chainring as concluded by a double blind test (dr Barani et al) executed with 19 testriders, also concluded by the team of the university of Chambéry, France etc..etc....Professional riders like Bobby Julich, Vinokourov , Voigt , Thierry Marie, Moreau, Brochard,.. etc.. make (or made) excellent results with this non-circular. O.symetric is conquering the triathlon top riders.

4. The model confirms the crank power efficiency of the Polclopek Oval (original crank orientation) as stated in

http://www.equusbicycle.com/bike/bicycles/Polchopek-oval-chainrings.jpg. Although the authors of the scientific work don't know how the power increase of the Polchlopek Oval, compared to circular, has been measured.

5.The model confirms the brilliant performances of the Rotor System Crank as concluded by several scientific studies carried out by prestigeous universities (a.o. prof dr Cordova et al., university of Valladolid, Castilla-Leon, Spain ) and further confirmed by excellent competion results of many riders.

6.The optimal crank orientation as calculated by the model has been confirmed by the practical tests done by Chris Bell, Highpath Engineering.These tests were excecuted with ergometer and by "endless" (trial and error) climbings of a steep hill with repeatedly changed crank positions versus major axis of the non-circular.

Access to the scientific study is given by following web-address:

www.noncircularchainring.be

Product development: O.symetric "Super" .

By implementing the conclusions of our study, an optimization of the O.symetric (non-circular chainring with the best potentialities) is possible, as well mechanically (stiffness, teeth orientation, teeth geometry, chain lifters, inner chamfers, aero...) as bio-mechanically (crank orientation vs major axis).

Reproduction or publication of (parts of ) the study is allowed on condition of mentioning the source and the authors (copyright).

With friendly regards

Gilbert Storme