What's your formula for freeing off a VERY stuck seatpost?

[rafiki]

Thanks all for your input. I wish I was in UK as I would be straight up to The Seatpost Man. For the time being I have ordered some Plusgas and will try dosing with that daily before my ride without seatpost clamp and try not to avoid too many of the washboard surfaces on the gravel.

 

[graham bowers]

Slide hammer.
The chain links will attenuate the force, a direct connection would be better if it doesn't work with the chain links.

View: https://www.youtube.com/watch?v=S3ek2GeZzE0

 

[palinurus]

My solution for the stuck seatpost on my hack (a late 90s Marin) was to just leave it stuck. Finally gave it to someone of similar height. That was years ago, it ain't coming out now.

 

[SkipdiverJohn]

The guy at Argos told me they melt out aluminium posts stuck in steel frames as a last resort. Braze melts at almost 300 deg C higher than aluminium (welded frames are even easier). Goodness knows what it does to the temper of the tubing, but they know what they're doing.

Most steel tubing used in bike frames isn't heat treated in the first place so there is no temper to worry about destroying. I would be very wary about using naked flame heat on anything made from Reynolds 753 though, because that was normally silver brazed at lower temperatures.

 

[rogerzilla]

There's not much 753 left now - it's all rusted out at the chainstays!

 

[PaulSB]

I once saw the Seat Post Man, he has a blue van with the name on it, parked on a side street handing over a bike to a customer.

I did wonder if the process was so secret customers couldn't visit his workshop.........

 

[andrew_s]

Aluminium corrosion products have a fair bit of water in them, and if you can drive it off the bulk reduces, making the post easier to get out.
If you've access to a hot air gun, try heating the post area up to 150° or so for a while, then add plusgas, leave it a while and tru again.

 

[andrew_s]

Another thing I've seen of is a DIY screw jack.
The lower half is a split block that bolts together round the seatpost just above the seatpost, not quite tight, so it will rotate but there's no way it will push over the seat tube/lug. The upper half is similar, with a slightly smaller hole so it clamps tightly to the seatpost, and t
There are 4 tapped holes vertically for M8 bolts.
Then just go round screwing down all 4 bolts a bit at a time to pull the seatpost straight out.

It will need access to someone with the facilities to make the accurately sized steel blocks.
Who knows, pehaps this is how the seatpostman does it.

 

[Ajax Bay]

Friday:

It's a steel seatpost in a steel frame.

The OP's exam question is a steel post in a steel frame (seat tube).

I doubt the Thorn Sterling has a steel post.

My initial reaction was also to harbour some doubt

The OP has edited his OP (without noting that a key element has been amended (from Fe to Al)).
Sunday:

It's an aluminium seatpost in a steel frame.

The other thread about freeing an aluminium seatpost in a steel frame is therefore pertinent.

 

[Globalti]

Some kind of jacking or pulley system that applies a ton or two of pressure would definitely work.

 

[Slick]

No fancy too,s or contraptions but I did buy a tin of plusgas which worked an absolute treat almost immediately.

All seat posts now greased and repositioned.

 

[MrGrumpy]

Might need to see about my carbon wrapped seatpost stuck in the aluminium frame. It ain`t budging, but could be an excuse for an N+1

 

[rafiki]

After starting this thread I thought I had better check the Thudbuster ST seatpost on my other bike - a 24 year old Dawes Mean Street XT. That seatpost has been in longer than my stuck Thudbuster so I wasn't hopeful. I undid the seat clamp bolt, gave the saddle a twist and the post slid out as if it had been installed yesterday!

 

[rafiki]

An update:
After trying many of the suggestions here (thanks again) without success I was in UK with my bike this week so I went up to Chorley and The Seatpost Man had it out in under 2 hours. He even managed to save the Thudbuster. Thanks John.

Bridgwater was on my way home so I called in to SJSCycles and they replaced the oil seal, hub bearings and gaskets on my Rohloff IHG so a very useful trip.

 

[gbb]

As a last resort, I would weld a 6" long bit of bar or box section steel to the top of the seat post and clamp it in a big bench vice using that - then twist the bike frame CAREFULLY in both directions, possibly with a piece of threaded rod clamped across the rear dropouts (like you would do if resetting the internal width) so you don't bend either stay in or out.
Before going to that extreme I would try multiple heating and penetrant spraying cycles, using a blow torch and diesel, ATF, or a mixture of both, in one of those little gardeners trigger bottles.

It's easy to underestimate just how stuck a seat post can bet, the method above in essense echoes my experience. In the end I sacrificed the seat post having tried everything, clamped the seat post in a ferkin big vice and used the frame for leverage. Despite gallons (not literally) of penetrant, it finally let out a huge cracking sound and then still required 10 minutes of grating, cracking sounds like a rusty gate amplified by 10 as it loosed little bit by little bit. Lots of effort, noise and luck.