chainstay

At many of the grand tours, the race organizer provides a transponder that is attached to either the chainstay or the fork.

Ask Nick: Tire disaster, the wheel behind the sticker, sequential shifts 2011

One specifically designed for Di2 will have internal wiring and the battery integrated under the left chainstay.

Tech gallery: Team Sky’s Pinarello Graal time trial bike 2010

All the growth in width happens on the non-drive side, so the crankset, drive-side bearing location, and right chainstay are unaffected.

Tour de France tech: Carlos Sastre’s Cervélo R5 2010

“What that gives us in the frame is space to make the down tube wider, seat tube wider, and left chainstay wider,” said Rinard.

Tour de France tech: Carlos Sastre’s Cervélo R5 2010

It's an early 90s Richard Sachs road frame I relegated to commuting duty when I noticed slight wheel rub marks inside the chainstay.

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Other frame features include a tapered head tube, 4mm of additional chainstay length over the race-oriented Xelius, and internal cable routing.

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The version for mechanical shifting also has internally routed cables, but the non-drive chainstay is thinner since it lacks the battery perch.

Tech gallery: Team Sky’s Pinarello Graal time trial bike 2010

A bike that self-destructs if you run into the chainstay?

Making A Point: Paint, Sponges, and Determination BikeSnobNYC 2010

While watching the Tour de France this year I noticed a piece of hardware on the riders' bikes that I did not recognize attached to the non-drive-side rear chainstay.

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Moreover, they're bolted to a Tirreno frame which appears to still have the warning sticker affixed to the left chainstay:

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