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I was reading a recent question when I saw this answer:

You should absolutely grease your seatpost (unless it is carbon fiber).

Why should I NOT grease a carbon fiber seat post?

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Anthony K
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6 Answers6

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Carbon parts will cause aluminum to oxidize, as a chemical reaction which is why seat posts wind up stuck in frames. But that isn't why this is necessary.

"Carbon grease" is not actually grease. It's a friction compound which increases the friction between your fancy carbon seat post and your frame. Increasing the friction allows a lower torque on the fixing bolts for the individual part, which reduces the risk of crushing the part, or having it slip in the frame.

Slippage of seat posts and handlebars in the frame was why we were originally told not to grease carbon parts. The grease reduced friction, which meant higher torque and more broken parts.

After parts started to get stuck, they realized that they need something, but it had to increase friction, rather than decrease it. Hence, carbon "grease" compounds.

zenbike
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  • If the seat bolt is tightened to the recommended torque and there is no slippage, is any carbon "grease" required? – sdgfsdh Dec 14 '19 at 13:14
  • @sdgfsdh good question! I would argue no, carbon paste/assembly compound may not be required in that case. With very light carbon posts, it’s possible that the seatpost’s recommended torque may be quite low, and that could be a clearer case for assembly compound. – Weiwen Ng Dec 22 '21 at 16:52
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As the person who made that claim, the reason is that allegedly some greases can attack the epoxies found in some carbon fiber applications, causing a breakdown of the CF structure, and causing expansion which will jam the post in place.

The epoxy will otherwise not corrode, so it's not necessary for that purpose. The manufacturers also recommend you do not do it.

I have a carbon fiber seatpost in a steel frame that I greased a long time ago before I learned about this and it isn't stuck, but I might just be lucky.

And of course, if you use a grease specifically designed for carbon fiber applications it negates all these claims, for they refer to the run of the mill stuff.

whatsisname
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    Actually, this is a myth. Carbon parts will cause aluminum to oxidize, as a chemical reaction. "Carbon grease" is not actually grease. It's a friction compound which increases the friction between your fancy carbon seat post and your frame. Increasing the friction allows a lower torque on the fixing bolts for the individual part, which reduces the risk of crushing the part, or having it slip in the frame. Slippage of seat posts and handlebars in the frame was why we were originally told not to grease carbon parts. The grease reduced friction, which meant higher torque and more broken parts. – zenbike Jun 20 '11 at 12:28
  • @zenbike Interesting comment. I believe the same thing holds true for aluminum nipples in a carbon wheel. You should post an answer. – Kellen Stuart Jun 19 '21 at 05:45
  • @kolob canyon: see below – zenbike Jun 20 '21 at 14:22
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You can get carbon seat post specific grease, it's designed to reduce the clamping pressure that is needed to hold the seat post in place and prevent it either sticking or slipping. Pace make some (Pace RC005 Carbon Fibre Seatpost Grease) and I'm sure some other people do as well.

Jackson
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  • And a carbon-friendly grease may be a solution to the question which originally started this discussion, about keeping the inside of the frame's seat-tube rust-free. Moisture can become trapped between carbon and the frame as well as any other seat-post and the frame... good to know that such a product exists. – DC_CARR Dec 14 '10 at 20:13
  • Assuming you're riding a steel frame with that carbon post? – zenbike Jun 23 '11 at 14:29
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I just confronted this problem exactly. Carbon post, almost "welded" into a Columbus SL seat post. I had removed it less than a year previously, but was now stuck so firmly the shop guys nearly had to destroy it to remove it (took over half an hour with the seatpost clamped into a vice, and two guys [carefully] applying torque on the frame to get it unstuck). The better the interior surface of the seat tube the better, then polished it to remove some brazing residue from the original assembly. They also applied an anti-seize compound to hopefully prevent this from happening again.

Tony Wood
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Lets just clear up a few basics: -There is conductive grease, and non-conductive grease. -Any "electrically dissimilar" materials that are conductive and in contact will "galvanically corrode" when wet. -Grease excludes the water from the interface between your two conductors ( steel/Alu bike vs carbon post. Carbon-Carbon is not "electrically dissimilar". -Carbon Grease is designed to insulate (non-conductive) and increase friction (small particles in grease). I believe the carbon grease products are silicone based dielectric greases w grit. -Conductive grease on dissimilar materials will galvanically corrode, slowly, with enough humidity.

John Munoz
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    Hi, welcome to bicycles. I'm not sure if you're saying that the carbon seat post should be greased or not. Please clarify your answer to the question. – DavidW Jul 28 '22 at 03:51
  • You're saying that carbon fiber will cause galvanic corrosion with steel or aluminum? I'd love to see references for that - it would add credibility to your answer. – FreeMan Jul 28 '22 at 17:51
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I'd imagine that there's no point in greasing it. You're not going to have any issue with it wanting to bond itself to the frame tube due to corrosion or dissimilar metals.

Brian Knoblauch
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    There are actually fairly common issues with exactly that kind of permanent bonding. See answers above. – zenbike Jun 23 '11 at 14:30
  • Interesting. Can't say I've ever seen it happen. I live in a fairly wet climate, maybe it only happens in drier places? Some other factor on why it would not happen to anyone that I know? – Brian Knoblauch Jun 23 '11 at 17:47
  • No idea, really. We live in a coastal area, with high heat and humidity (Dubai), but before here, I lived in Seattle, which is cool and consistently wet. Perhaps the salt in the air? But we've had consistent and similar issues in both places. It does tend to happen when the post is left in place for an excessively long period of time, without maintenance. – zenbike Jun 25 '11 at 07:35
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    There is a great post by @lantius here which explains the issue in detail. http://bicycles.stackexchange.com/questions/4508/metal-seat-post-with-carbon-fiber-frame/4514#4514 – zenbike Jun 28 '11 at 11:48