The Ricardo and the frozen seat post

August 30, 2009

I have written about this before – my 1981 Ricardo with the totally seized Sugino allow seat post. I like this bicycle a lot. It is Chromoly, quite light, has Shimano 600, metal toeclips, light cranks and is overall in pretty good nick, if a bit scuffed and rusty in parts. I want to ride it more than I have and I’ve invested a fair bit of time getting overhauling pretty much every bearing and polishing up what was a forgotten relic of the early 80s. The bike is a little big for me so if I could get the seat post down four centimetres or so it would make the world of difference – but it is stuck.

Over the last year or so I have squirted WD40 down the post, lent on it with monkey wrenches and hit it hard with a mallet. This weekend I went at it again with my neighbours advice to use Penetrene and a heat gun on it. After three days and nights of feeding Penetrene down it to applied the heat gun to the post at nearly 500 degrees until the frame got too hot to touch and let it cool down four times hoping the alloy would expand and contract enough to break its hold. It hasn’t.

So I went back to my original reading.. the (late) master of all things bicycle – Sheldon Brown and his writings on stuck seatposts:

The torch technique is worse than useless when you are dealing with an aluminium seat post stuck in a steel or titanium frame, because aluminium expands twice as much as steel, and 2 1/2 times as much as titanium for the same increase in temperature. In fact, the exact opposite technique will often do the trick for aluminium seat posts–cool the seat post down as rapidly as possible. The contents of a CO2 tire inflation cartridge applied inside the seat post can shrink it down just enough to do the trick.

He also adds that Penetrene type solutions do nothing with aluminium as well.

Aluminium seat posts frequently become stuck by corrosion also, and penetrating oil is almost useless against aluminium oxide. Fortunately, aluminium oxide can be dissolved like magic by using ammonia.

So the next plan is to either just waste a CO2 cartridge around the post or take out the bottom bracket (again!) and pour some ammonia down there… or a can of coke!

Get a can of Coke and pour it down the seat-tube and let it sit overnight. Seriously. I don’t know much about chemistry, but there is something in carbonated sodas that loosens up seized parts. Just be careful once you get the seat post to budge that you don’t get coke all over the place, and flush it out thoroughly with some sudsy water so you aren’t wondering where all those ants are coming from next summer. Western Bike World (among many references)

I’ll keep you updated.

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