30 December 2014
When attempting to move a Cannondale carbon seat post in a carbon frame in order to match saddle-to-crank distance exactly, is it appropriate to bang on the saddle to get the post to move two millimeters?
(This is Miss Piggy after all. A certain amount of brute force is expected. Try removing the rear wheel some time.)
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3 comments:
There is probably carbon paste in the seatpost-to-seattube connection. While metal-to-metal surfaces will usually have some kind of lubricant to reduce oxidation or electrolysis between the surfaces, or even a mixture to eliminate galling (see the "Ti-Prep" used for titanium-to-titanium surfaces), the torques used on carbon are low enough that you may not be able to get the clamp tight enough to hold without grinding the epoxy matrix that holds the carbon fibers in place. The carbon paste is, essentially, a weak adhesive that holds the tube in place; it provides just enough additional friction at the low torques used on carbon frames that the seat post, for example, won't slip down while you're riding.
That said, the carbon is NOT going to be happy with a hefty hammerin' to move the goods. I'd suggest loosening the seat clamp, giving the doin's a sharp rap with, say, a good, hefty rolled-up magazine, and seeing what you get. Do NOT hit with wood or metal. If you have a rubber mallet, that might do it. (Is the cross-section of the post circular or "aero"? Can you twist the post in place?)
I used a minimum of violence. I banged on the saddle with my fist and my palm, just enough to move it a couple of centimeters.
It's an aero post, the first I've encountered. Round ones are easy. They wiggle.
Your fist and palm are just the proper mallets to use under the circ's. I expect things will be fine. Still, I expect you'll begin to see why I'd rather deal with metal parts...
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