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Old 02-20-08, 05:34 PM
Eschew Obfuscation
SesameCrunch's Avatar
Join Date: Aug 2005
Location: San Francisco Bay Area
Posts: 3,845

Bikes: 2005 Fuji Professional, 2002 Lemond Zurich, Folders - Strida, Merc, Dahon, Downtube, Recumbent folder

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Originally Posted by jur View Post
I'm actually about an inch beyond max extension. I checked the end of the post where it sits with respect to the frame joints, and it is still below the top tube (or is that downtube?). So I don't think I will damage the frame. The post is another matter. That may bend. I have a piece of very tight-fitting 1" ally tube inserted inside the seatpost for added strength and stiffness, but obviously it is not stiff enough. I think the bounciness is therefore caused by the springiness of the post, not by minimum insertion issue. The post's srping plus my upper body mass gives a particular resonant frequency coinciding with 100rpm. A stiffer post would shift that frequency up, say to 120rpm, and since I don't pedal there, that would solve the problem.

I also have my seatpost extended about 1" beyond max. As you know, I used a wood dowel (pine) to reinforce the seatpost. I have not found seatpost flex to be an issue for me. The wood does not allow for the kind of deflection you're describing. (I weigh 188 lbs.) It's not as glamorous a solution as a carbon seatpost, but it's certainly cheaper. I would recommend it as something you could try.
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