When to use carbon paste

[vqdriver]

Excuse my ignorance. The only time I've had a carbon seatpost was on a carbon bike and I've never put anything on it, paste, grease or otherwise. I figure it holds fine without overtorquing and plastic doesn't stick to plastic... So far.

But perusing some threads I'm unclear if there's any need when putting it on a steel frame. It seems counterintuitive that anything will freeze to carbon but I thought id throw it out there. So far I haven't noticed any slippage or twisting and Ive actually tightened the binder less than spec.

I can just leave it alone right ?

[gearguywb]

On my Desalvo I had to use carbon paste to hold the seatpost otherwise it slipped. Part of the appeal of the carbon paste is it allows clamping and holding without overtorquing.

[TimmyB]

as gearguywb mentioned, the advantage of carbon paste is that it enables you to use less torque to hold your carbon seatpost/bars/derailleurs/etc in place with as little torque as possible. this decreases the chance of you cracking your carbon parts. if you're asking if it's a good idea to use paste for a carbon post in a steel frame, then the answer is yes. You run the same risk of overtorquing your seatbinder bolt and cracking your carbon seatpost with a steel frame as a carbon frame. If you're asking if paste is necessary for an alloy post in a steel frame, probably not, as the tolerances for both materials is so great. that being said, "if it ain't broke, don't fix it" as they say....

EDIT: Disclaimer: I'm paranoid with carbon and use paste + torque wrench for everything on the bike

[forrestw]

The main reasons that seatposts can become horribly stuck in steel are that iron oxide occupies greater volume then the iron it comes from, so in a tight fit it expands to more than the available space effectively creating a press fit. Aluminum SPs are most highly prone to this because Al is relatively soft and quite prone to galling (aside .. I believe, but have no proof that this is exacerbated by chemical reactivity between iron oxide and Al aka thermite reaction).

Anyhow, I always want *something* inside a steel seat tube to prevent rust from forming, in the case of the carbon compound it may be better due to the notes above about reducing necessary clamping torque (where grease would increase necessary torque). Zinc anti-seize would seem like a good compromise in this case but that's a guess, not a tested method.

[Charles M]

Forrest wins.


And there's a difference in pastes folks.

Motorex (http://www.pezcyclingnews.com/?pg=fullstory&id=8474) is the only stuff Ill use now.

http://www.pezcyclingnews.com/photos/tech/motorex/motxllpvg.jpg

[Mark McM]

It seems counterintuitive that anything will freeze to carbon but I thought id throw it out there.

Well, you need some kind of insulation between carbon and metal, or you run the risk of galvanic corrosion - this is especially true when joining carbon and aluminum. Back in the '90s, when aluminum lugged carbon tube frames were common, frame failure due to galvanic corrosion at the joints was not uncommon if the carbon tubes weren't properly insulated (for example, a thin layer of fiberglass was sometimes applied on the ends of the tubes to insulate them from the metal lugs).

The clearcoat layer or epoxy on the seat tube may be enough to insulate the carbon from the frame, but a slathering of assembly paste can't hurt.

[benb]

Will a carbon seatpost & Ti frame bond?

I'm not real worried because I do use the carbon paste stuff.. but I'm curious how often the seatpost should be removed. My particular combo will slip without the paste.

[flydhest]

Forrest wins.


And there's a difference in pastes folks.

Motorex (http://www.pezcyclingnews.com/?pg=fullstory&id=8474) is the only stuff Ill use now.

http://www.pezcyclingnews.com/photos/tech/motorex/motxllpvg.jpg
Where do you buy it? (heavy sigh, they prolly send it to you, don't they?)