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Bike Geometry question.(3 posts)

Bike Geometry question.cyclinseth
Jan 29, 2002 5:38 PM
How does bottom-bracket height affect fit, ride characteristics, handling, responsiveness? And what is considered a high bb and a low bb?

Thanks
re: Bike Geometry question.g
Jan 29, 2002 6:04 PM
Try posting at this board too. http://www.bikeschool.com/technical-board/tech_postings.html
The Stilt Step Factor.guido
Jan 30, 2002 11:00 PM
That's the title of an article at the Rivendell website:

"With stilts, if you put the step down low the tops wobble all over--something to do with a longer lever-- but once you get your balance you can thread a needle with the stilts. When you raise the footpegs, the tops stabilize (the lever shortens) but the feet are harder to direct."

To make an analogy: The stilts are the bike, the steps are the pedals, and the feet are the tires.

The closer the pedals are to the ground, the shorter this "leverage" is, therefore the more precise the bike handles, the easier it is to stay upright, the better it holds the road, even as you move around above the top tube, or lean into a corner. My old DeRosa has the stability of a touring bike even though it has a 74 degree steering angle. It's BB "drop" from the wheel axles is 7.5 cm. Standard for road bikes is more like 6.5 cm.

Eddy Merckx, Richard Sachs and others have also built with low BB heights. The trade-off: forget about pedaling through corners!