Steel and aluminium...

spasypaddy

... does not mix.

now ive found this out the hard way with my steel fixie and its aluminium seat post. now having had a bike fit on my main bike i need to move my saddle on my fixie. it hasnt been moved in a very long time.

Now it doesnt move. it wont budge a mm. properly seized up.

Ideas? i really need to move the saddle up.

unixnerd

Heat can help in a situation like this. Try leaving the bike in strong sunlight for a few hours then tapping the top of the seatpost with a hammer, downwards into the frame (remove saddle first!). Ideally you'd want more heat but it's hard without damaging the paint, you might try a heat gun but be careful.

spasypaddy

will the steel expand quicker than the aluminium?

litttlestwoo

h h h

spasypaddy

when you say acetone do you mean nail polish remover? and should i keep pouring more down there?

should i turn it upside down and pour it down through the bottle cage mounts?

litttlestwoo

h h h

redddraggon

acetone or ethyl acetate will not dissolve Al2O3 which is what the corrosion will be, as Al is a more reactive metal than Fe.

If you want to remove the corrosion (Al2O3) you need AMMONIA not bloody Nail Polish Remover.

litttlestwoo

Aggression, I'm off, got a bike to ride...what is it with type A's?

redddraggon

litttlestwoo wrote:

I'm off, got a bike to ride...

At this time of the day?

litttlestwoo

ddraig goch.. mae e wedi blino... bendith

spasypaddy

so i want to put ammonia down my seat tube?

unixnerd

will the steel expand quicker than the aluminium?

No, the opposite. But the steel is in the path of the heat and will expand first as there's less than optimum thermal coupling between the two parts.

Monty Dog

Sheldon Brown has all you need to know on stuck seatposts

spasypaddy

cheers monty i shall go and have a read!

spasypaddy

ok according to sheldon i need ammonia, how much would i need and what would be the best way to apply it? how long does it take?

Mister W

Steel frames and old aluminium seatposts are a nightmare. Aluminium oxide takes up a larger volume than aluminium and it very hard so as the seatpost corrodes it gets wedged more tightly in the frame. It's impossible to release it with many of the normal tricks, like penetrating oil or a mild corrosive, such as coke, because they can't get between the aluminium oxide and the steel. It's also difficult to do it with heat because, as someone's mentioned, the aluminium expands quicker than the steel. The only way to do it is by dissolving the aluminium oxide using ammonia but the success of this will depend on how long the seat post has been in the frame and how patient you are.

spasypaddy

the seatpost probably hasnt been moved for a year. how long would the ammonia take to work?

over night? 2 days?

could i just pour it down the seat tube (via the bottle mounts)?

would cutting it out be easier/quicker?

i would have no problem with replacing the seat post if its going to save me a huge amount of time and effort...

Buckled_Rims

I feel the pain, I ruined my steel framed bike with an Alu seat post when it was stuck. I tried everything. But there's been a few good posting on this forum. Some suggestions.

1. Ream the seat post out.
2. Ammonia (didn't work for me).
3. I think one of the MTB guys (supersonic or Nicklouse) mentions using butene gas??? :shock:


I think reaming is probably the best bet if you think it's really stuck in. If you can get it to within a few millimeters thick the post should start to collapse.

spasypaddy

what do you mean ream?

Buckled_Rims

spasypaddy wrote:

what do you mean ream?

Reaming is like a drill or milling tool. It'll drill the inside of the post out. It needs to be done carefully of course. Once the Alu post is only a few mm thick, it should come out.

The other option is one of those hammers (who's name I can't remember as usual :x ) but it slides a weight on the rod. This would hammer out the post from the inside of the frame with the correct tool end.

spasypaddy

ok well i went to one of my other LBS and on their recommendation got some stuff called plusgas (cost me £3) from the local garage. they reckon it will work and so did the garage. May take 24hours but it needs to soak in.

will give that a go this evening/tomorrow and see what happens. hopefully it will work and then i either need to get some good grease or a carbon seat post

sheffsimon

spasypaddy wrote:

ok well i went to one of my other LBS and on their recommendation got some stuff called plusgas (cost me £3) from the local garage. they reckon it will work and so did the garage. May take 24hours but it needs to soak in.

will give that a go this evening/tomorrow and see what happens. hopefully it will work and then i either need to get some good grease or a carbon seat post

Maybe, maybe not. Its a penetrating oil, but as posted earlier, needs to get in the gap between alu and steel, which is filled with ally oxide.....

Cut the f****r out with a hacksaw blade.

spasypaddy

they said its what they've used if it doesnt work it was only £3. not the end of the world.

i fear cutting it out maybe on the cards, however i down own any suitable tools and i may have to make a trip to my mates workshop

sheffsimon

spasypaddy wrote:

they said its what they've used if it doesnt work it was only £3. not the end of the world.

i fear cutting it out maybe on the cards, however i down own any suitable tools and i may have to make a trip to my mates workshop

Hacksaw blade with a rag round it. Not a thick rag obviously, cos then it might be comfortable and not dig into your hand.

Anyway, crack on.

Avoneer

I'd try fitting an old saddle and hammering it to death with a hammer (up and away from the frame and trying to spin it round) to try and break the corrosion (after the plusgas and/or amonia) before cutting - that'll be a world of pain.

Pat...

spasypaddy

my mate has offered to cut it out for me if the plusgas doesnt work.

El Gordo

Does the cutting it out with a hacksaw blade approach really work? I can only imagine ending with with a frame with a sliced seat tube and a bleading hand. Perhaps other people are more adept with saws than me!

What worked for me was fitting an old saddle and belting the side of the nose with a 4lb lump hammer repeatedly with ever more fury. Fortunately the corrosion gave way before the frame, saddle or seatpost. It was an old mountain bike though - I wouldn't get so violent on a 'nice' bike.

huuregeil

Getting a stuck post out is a monumental waste of time, money and effort. You'll find that steel framebuilders will (try to!) remove them for you for around the £25 mark - definitely worth considering as an option, not least because they have the required kit (torch, reamer) and the experience to do the job properly.

spasypaddy

thanks huuregeil, if the plusgas doesnt work my mate will cut it out for me (hes a mechanic at a bike shop) probably wont even cost me a few beers.