Cannot adjust Bike seat

harry999 · 03-12-2019 2:39pm #1

I open the screw holding the bike seat in place & even with screw open bike seat will not move - totally jammed. I gave it a few belts of a hammer and still no move... I was thinking of maybe trying the car jack - by putting the car jack on cross bar and see if it jack up the seat... Any ideas ?? Thanks

cdaly_ · 03-12-2019 3:41pm

Don't use a car jack. You'll more likely damage the crossbar that way.

The usual thing is that a mix of aluminium (frame) and steel (seatpost) end up welded to each other and can be very difficult to separate.

The traditional way is to clamp the saddle (or a sacrificial one) in a vice and rotate the frame around the seat post.

Cee-Jay-Cee · 03-12-2019 3:48pm

Get any descaler that uses phosphoric acid and turn the bike upside down and dribble the descaler into the seat tube from the bottom bracket. Use duct tape around the seat post at the point where it goes into seat tube to prevent the descaler from leaking out. Leave it over night and drain out the descaler and remove your seat post. It works very very well!!

Weepsie · 03-12-2019 3:50pm

Is it an alu fram and alu seat post? Steel and alu, carbon and alu?

Depending on the mix of materials, the bond/seizing can be a reasonably easy fix or a PITA. Steel and Alu will just bond together, and may need to be cut out or melted out. This is the nuclear option.

IF you're able, take out the bottom Bracket, tip it upside down and squirt in some really good deseizing lubricant like plusgas. Leave it soak for a few days, pour it out and then try to remove it.

Didn't work for me, with repeated tries, but mines fairly welded in there.

Another option is a slide hammer. Take saddle off, somehow attach it to the clamp, and use the slide hammer to effectively pull it out. Or a really, really long lever clamped on somehow, and then use that to twist it.

All have risks, and can damage frame, but still

07Lapierre · 03-12-2019 4:06pm

Here you go. (Best of luck! )

https://www.youtube.com/watch?v=54WhdrLKKvY

check_six · 03-12-2019 6:25pm

Is a heat gun any use for this type of thing? I've been using a heat gun on a bunch of difficult to budge stuff recently, and I don't know why I wasn't doing it for years as it works very well. I haven't tried it on a seat post though, and I'd be wary around any exotic materials like carbon fibre.

magicbastarder · 03-12-2019 6:29pm

can depend on what the mix of metals is - aluminium expands more under heat than steel, so if it's an alu seatpost in a steel frame, it may make it even harder to budge. if it's the other way around, it should make it easier though.

harry999 · 03-12-2019 7:56pm

Thanks for the above - it's an alu seatpost in a steel frame.

I tried the hot water + taken off the saddle + a few belts of hammer => But no move at all...

saccades · 03-12-2019 9:23pm

Dunk it in caustic for a week.

Feidhlim Dignan · 03-12-2019 9:59pm

Boiling water. I have used boiling water to heat a carbon frame enough to get some movement on a alloy post, it was pretty easy after that.
I'd imagine it would be good on a metal frame too.
Best of luck, don't rush it

railer201 · 03-12-2019 10:36pm

WD40 is pretty good at dissolving corrosion, just bit by bit application and plenty of firm taps on the seat post with a hammer, using a piece of hardwood as a dolly, to protect the seat post. Also use a wooden block, as a support, under the bottom bearing bracket to 'back off' the hammer taps and avoid any damage.

The continual shocks from the tapping should loosen up the corrosion to let the WD40 slowly penetrate between the seat post and frame.

Weepsie · 03-12-2019 10:39pm

Plus Gas or Arctic Hayes Crack it would be better than WD40.

If it's oxidised though, none of them will be much use.

Caustic soda is nasty stuff though, and you'll be probably wrecking paint too.

railer201 · 03-12-2019 11:42pm

harry999 wrote: »

Thanks for the above - it's an alu seatpost in a steel frame.

I tried the hot water + taken off the saddle + a few belts of hammer => But no move at all...

Depending on how far the seat post extends into the frame, you might as a last resort consider cutting it 'length ways' with a hacksaw blade. As it will be scrap, shorten it first, leaving enough protruding so you can refit the saddle, or use visegrips, or stillson wrench to twist it out.

To avoid bending the blade, cut on the draw stroke rather than the push stroke and wrap the appropriate end of the blade with plenty of insulation tap to protect your hand.

Some useful information here on this procedure - https://www.bikeforums.net/classic-vintage/719298-tips-hacksawing-out-stuck-seatpost-2.html

straighttohell · 09-12-2019 4:45pm

Yes, I ended doing what railer201 describes as a last resort. To cut a long story short.... it worked. A horrible job took days but salvaged my bike and was worth the effort. Use a fine tooth hacksaw. Try to cut a few 'slices' and wedge in whats left. It's a stinker to have to dump a decent frame due to a stuck seatpost

harry999 · 09-12-2019 5:12pm

Ok Tried the hot water again at the weekend - still no move on saddle...

Anybody else try the phosphoric acid ? Does this work ? and what household product will have phosphoric acid ? Thanks

cletus · 14-12-2019 11:32pm

Have you got any further with this. I removed one recently using a bench vice

Cee-Jay-Cee · 15-12-2019 12:35am

harry999 wrote: »

Ok Tried the hot water again at the weekend - still no move on saddle...

Anybody else try the phosphoric acid ? Does this work ? and what household product will have phosphoric acid ? Thanks

Is there a Homestore near you? They have descaler (usually used for cleaning kettles/coffee machines etc) Shouldn’t be too expensive.

It does work and very effectively, just make sure to seal the top of the seat post and seat tube so it doesn’t leak out as it needs to soak in for a day or two to work.

Watch this video >> https://youtu.be/Kc37Ab8B580

Cannot adjust Bike seat

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