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Olympic Tech: Bobby J and his funky chainrings

When Bobby Julich crossed the finish line just 26.45 seconds behind teammate Tyler Hamilton in Wednesday’s Olympic individual time trial, it wasn’t just a victory for a man and his country–technology also won in the streets of Athens. Helping to power Julich’s bike were two very unusual chainrings that could very well transform the way we propel our bicycles in the future. Julich was riding a pair of French made, out-of-round, “Osymetric” chainrings which Julich claims have helped him all season. Now before you say, “Biopace,” think again. In a phone interview with VeloNews from France

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By Andrew Juskaitis, VeloNews Technical Editor

Today in Athens

Today in Athens

Photo: AFP

Olympic Tech: Bobby J and his funky chainrings

Olympic Tech: Bobby J and his funky chainrings

Photo:

When Bobby Julich crossed the finish line just 26.45 seconds behind teammate Tyler Hamilton in Wednesday’s Olympic individual time trial, it wasn’t just a victory for a man and his country–technology also won in the streets of Athens.

Helping to power Julich’s bike were two very unusual chainrings that could very well transform the way we propel our bicycles in the future. Julich was riding a pair of French made, out-of-round, “Osymetric” chainrings which Julich claims have helped him all season.

Now before you say, “Biopace,” think again. In a phone interview with VeloNews from France designer Jean-Louis Talo was clear to point out that his patented out-of-round chainrings are considerably different that Shimano’s original Biopace and Biopace II chainrings.

“Biopace did very little to address the dead-spot in a rider’s pedaling stroke,” Talo asserted. “My chainrings are designed to optimize the power portion of the stroke while minimizing the dead-spot. If you look closely, you can see my chainrings aren’t just oval or elliptical as others have been, but shaped entirely to take advantage of a rider’s leg musculature. The geometry we use is two successive curves having a unique symmetry, both with a central point of rotation. When the pedal is up [at 90 degrees] a rider’s strength is minimal so the ring radius is small as well. When the pedal comes near to horizontal, the rider’s strength is more, so the chainring is bigger to take advantage of that. Unlike Biopace, my rings constantly change radius to take full advantage of the complete power stroke of a rider. This is the first time this has been accomplished in a chainring.”

Talo pointed to some of the impressive data that he claims was obtained from independent testing carried out in Europe. He reports improvements of between 5- and 15-percent gains in efficiency which can result in a 3-percent gain in speed (given identical input effort). Talo also claims his chainrings can help alleviate chronic knee stress issues by providing more mechanical advantage when a rider’s knee is bent at 90 degrees (one of the most stress-prone positions of a rider’s power stroke).

This isn’t the first time Julich has raced the Osymetric chainrings. It was almost one year ago that we saw these strange looking rings on Julich’s bike in Hamilton, Ontario Canada during the 2003 World Road Championships. There he claimed that the rings, “we good for 5 seconds per kilometer.”

Julich used the unusual rings at the Vuelta a Pais Vasco this year, where he beat Hamilton (Phonak) by less than one second in a time trial at the Spanish stage race. Julich also raced the technology in the climbing stages of this year’s Tour de France, although he chose to run only the inner ring to satisfy his Shimano sponsorship.

The Osymetric rings are not brand new to the cycling world. In fact, Talo has been testing variations of his rings with professional teams, including the old Festina team, as well as individual riders – Jens Voigt, Alexander Vinokourov and Julich – since late 2000. Talo reports that riders favor the rings for climbing, and also feel they’re an advantage in heavy-power flat stages (i.e. TT). The chainrings aren’t’ yet available here in the United States, but should soon be available through a major distributor (by Interbike Talo commented.)

If Julich’s Athens success is any evidence of the rings’ advantages look for resurgence of interest in out-of-round rings in the near future. One of us at VeloNews will be among the first North Americans to obtain the rings, so stay tuned for a report in an upcoming issue.

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