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07-12-09, 02:26 PM
I was cleaning up my bike and noticed a hairline "crack" on the tip of my seat post. It's a 2008 Bianchi Pista Concept track frame:
The crack only appears on the exterior and I don't see any stress marks on the inside of the tube. I only ride this frame in the park and on the track.
Anyone have any ideas?
It could be simply a stress crack in overly brittle paint, but it looks more like it's in the metal. You might watch carefully to see if it widens when the clamp bolt is cinched, but the only way to know for sure is to remove the paint and check the metal beneath.
If you're concerned and want decent post holding power with reduced stress, consider using coarse lapping compound (available in auto stores) in lieu of grease in the clamping zone of your post. The grit engages both the post and frame providing lots of holding power without having to tighten the clamp as much. (it's the same principle as throwing sand under tires for traction on ice)
BTW, if it is cracked, you can carefully file it down to a standard diameter, and fit a replaceable alloy clamp. It takes a bit of hand skill and patience, but isn't really difficult - a perfect DIY project to save a frame for little or no $$$.