aluminum seatpost in carbon frame - grease the post or not???

[eddief]

Found the least agreed to subject in bike lore. To grease or not to grease? Most internet conversation is about carbon posts in carbon frames or other frame media too. No concensus anywhere.

My question is about an aluminum post in a carbon frame. A seattube that is plain old carbon with no fiberglass or aluminum liner.

[Frustration]

Maybe the question is why grease?

[Peter P.]

I recommend anti-seize compound as a first choice, grease as a second.
Why? It's not a bearing surface, so you don't need a lubricant; your concern is seizing in the frame.

Why should you NOT try to go without? Because it won't hurt to go WITH grease/anti-seize. However, if you go "nude" and the post freezes in the frame well, let's just say I told you so.

The big topic of debate is slippage caused by the grease in carbon or rumors of grease breaking down the carbon. Unless the frame manufacturer specifically mentions grease as a no-no on your frame, don't worry about it.

[eddief]

just pick something up at the auto parts store?

Thanks for the info. Makes sense.

Here's a point of view:

Here's the closest thing that I found to galvanic corrosion
between carbon fiber and aluminum. It seems to suggest that
that salt water is required, if not an actual wooden leg and
whaling ship:

Galvanic Corrosion

The corrosion of metals and semiconductors involves the flow
of an electric current within the material. Most of the
constituent materials in fibre-reinforced laminates are
insulators and, in consequence, electrochemical corrosion is
not an issue. However, carbon (graphite) acts as a noble
metal, lying between platinum and titanium in the galvanic
series. Carbon fibres should not be used where they can
come into contact with structural metals (especially
aluminium or magnesium) in the presence of a conducting
fluid (eg sea-water). A thin glass fibre surface layer may
be sufficient to prevent the formation of such a galvanic
corrosion cell.

http://www.tech.plym.ac.uk/sme/mats324/MATS324A7%20EnvResist.htm

[vaxn8r]

I've used AL posts in CF frames for 10 years. No lube needed. Stick it in dry and forget about it. Sounds mp but in this case not.

[Climb01742]

i second what vax said. again just personal experience but i've had no issues with alu into carbon.

[stevep]

grease it. or anti sieze

[Climb01742]

grease it. or anti sieze

steve, just curious (as you know your carbon): why grease? i've never had any issues. have i just been lucky? metal to metal has siezed on me but never alu in carbon. thanks for the enlightenment.

[93legendti]

I've used AL posts in CF frames for 10 years. No lube needed. Stick it in dry and forget about it. Sounds mp but in this case not.


Had an alu post in my Trek 5500 for 6 years, no grease; no slip; no seize.

[stevep]

there is no harm being lubed. if they do freeze the frame can be ruined.
its like the negative lottery....at least you wont lose.
some riders sweat a lot, ride where it may be wetter than other places... and are hammered by this. others dont ... clearly not a problem for all.
to remove a frozen post in a frame ( esp a lightweight frame ) is a mechanics nightmare.
just trying to save some poor mechanic a huge headache somewhere.
alloy, carbon, ti...frame or post...grease 'em all.
and an additional note ..if you have 8 inches of post inside the frame you are begging for trouble. cut off the post until you have 4 or so in there...
dont tempt fate.

[cydewaze]

When I built up my replacement frame from Trek, I used white lithium grease to lube the post. It started slipping. So I pulled the post and cleaned it off, and also cleaned out the seat tube.

It still slipped, so matter how tight I cranked down on the bolt. Turned out the seatpost collar the LBS gave me was the wrong size. I put a new collar on and it holds fine. I suppose I should re-lube it sometime.