Carbon seat post / aluminium frame

timbo_tim

Hi all

Yet another stupid question I fear, but wanted to canvas opinion on the best way of installing a carbon seat post in an aluminium frame? There appears to have been no lube / carbon paste etc installed on purchase but am thinking it might benefit from some? I removed the seat post last night and it was quite stiff to move, and there must have been some grit inside as the bottom half now has some lovely zig zag marks (thankfully since I am only going to ever shrink and have to move the post down not up, they wont be visible). So going forward, should I be doing something different??

I found this

http://road.cc/content/forum/72834-carbon-seat-post-alloy-frame

Copied from another site :
From Easton:
No grease on carbon posts. Grease contains certain minerals that can attack clear coats, can penetrate the resin matrix and could cause swelling of the composite laminate. Can you say "stuck seat post?" Don't use grease.
John G. Harrington
Vice president, bicycle products
Easton Sports, Inc.

From Campagnolo:
No grease. In some cases it can be dangerous to use grease as the chemical composition can cause a reaction between materials. Besides, it increases the torque required to clamp the post.
Richard Storino
Campagnolo USA

From Deda:
Absolutely no grease on carbon, ever. Also, do not use solvents to get old grease off, or to get old grease out of the seat tube. John Harrington of Easton and I believe that many solvent residues in the seat tube soften the gel coat of the carbon, then bond the gel coat to the inside of the seat tube, freezing the seat post in position for eternity.
Tom Franges
Deda Elementi North America tech support

and it suggests there shouldn't be any lube / grease / slip / paste etc, so wondered if the hive mind on here disagreed?

Thanks
Tim

keef66

My first experience with a carbon post and an alu frame:

The bike shop that built it up initially used nothing, but I found that the seatpost kept slipping down despite adequately tightening the clamp bolt. I'm only 5'6" / 10 stone, and don't go riding through potholes...

The bike shop sent me a little sachet of carbon assembly paste to try; I gave the seatpost a light coating and reinserted it.

The seatpost now stays put without having to tighten the clamp too much. I've subsequently bought a pot of the carbon paste, and whip the post out every 6 months or so for a quick wipe down and reapplication. I also think that this routine will help prevent any corrosion.

More recently I acquired a carbon frameset and built it up with an alu seatpost, so I do the same with that too.

If yours isn't slipping, and it was quite tight to start with, I'd probably say use nothing, but whip it out every few months for a wipe down. The carbon paste contains tiny plastic beads and feels gritty, so it does take up some space. You'd probably scrape it all off inserting a really tight seatpost.

grenw

Have carbon posts in aluminium frames on my mtb and road bike. I've always used carbon paste and never had a problem. Clean them every few months - more just to make sure they haven't got stuck than for any other reason.

timbo_tim

Thanks both - that is perfect and exactly what I needed to hear! I too had to tighten up too much, and think that's why I ended up with an almost stuck post. Will clean down and get some paste - any recommendations greatly appreciated!

keef66

Think mine's Pace; no idea which of the many online retailers I got it from because it was 8 years ago. Little tub that will last longer than I do...

I'll have a Google

Bobbinogs

Yepp, carbon assembly paste works very well...although I wished I had taken my post out, cleaned and re-inserted at regular intervals as it is now firmly stuck and nothing seems to want to shift it. Schoolboy error that I am ignoring in the vain hope that if I don't think about it then it won't be a problem :oops:

sungod

never seen any scientific/engineering evidence that composites made with cf+resin have any problems with grease, nor had any problem in years of using grease-based assembly compounds on cf and of various cf components having grease all over them

there are cf frames, chain rings, cogs, cranks, spiders, pedals, shoes, derailleur bits, steerers, seatposts, stems, bars, these all seem to survive grease and oil perfectly well, as do cf parts in other industries

as far as clearcoat goes, if a manufacturer of bike parts is using a clearcoat that can't handle grease, their products should be avoided as they clearly have a singularly poor understanding of bikes and the real world!

the quoted comments originated in the usa and have the feel of reflex liability avoidance to them, plus a fair dollop of irrationality: replace the word "grease" in the quotes with the word "cheese", they make just as much sense either way

crankycrank

I did some research on this over a year ago and the verdict is mixed from some pro mfrs. I can't remember who said what but there was at least 1 guy and very well regarded as one of the gods of custom CF bike builders in the US that said grease was no problem. And as SUNGOD mentioned it would be kind of dumb to build a bike with CF parts that are damaged by grease when these parts are traditionally slathered in the stuff by most bike owners. CF hubs have grease in their bearings, CF mechs with oil and grease, CF brake/shifters have grease inside, Headsets in CF headtubes, etc., etc. CF paste for the seatpost does make sense IMO as it helps the clamp grip the post with less torque resulting in less chance of cracking any tubes, and it's cheap.

Harry182

FTW -