Joined: May 2008
Posts: 10,106
Likes: 2,757
From: Fredericksburg, Va
Bikes: ? Proteous, '65 Frejus TDF, '73 Bottecchia Giro d'Italia, '83 Colnago Superissimo, '84 Trek 610, '84 Trek 760, '88 Pinarello Veneto, '88 De Rosa Pro, '89 Pinarello Montello, 'Litespeed Catalyst'94 Burley Duet, 97 Specialized RockHopper, 2010 Langster
Cutting up the seat post is a last resort before using lye.
Give the penetrating oils time to work. Include a couple of gentle taps with a hammer to help the pentrant to "move."
And you are right to be careful. others have broken the CS joints at the cluster trying to twist it off using the frame and the post in a vice.
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