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PostPosted: Sat Oct 26, 2013 1:54 am 
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Joined: Fri Oct 28, 2011 3:25 am
Posts: 1311
Location: United Kingdom of Great Britain and Northern Ireland
By 'bicycle grease' I mean like NLGI 2 grease with Teflon or ceramic additives - the industry standard kind of stuff from people like Finish Line. Presumably, this stuff is traditional petroleum-based grease. I am conscious of the availability of eco-type, biodegradable greases, like the stuff we have from Pure in the UK, and which are likely to be a whole lot less nasty.

And I mean 'bare carbon fibre' like you get on the inside of a head tube or at a fork crown, assuming the user has greased the outside of cartridge headset bearings before fitting them in the headset cups.

Thanks.


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PostPosted: Sat Oct 26, 2013 7:50 am 
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Joined: Fri Dec 24, 2010 9:37 pm
Posts: 912
Location: it's raining, it must be uk
no, it's an urban myth

the 'bare' cf is still embedded in epoxy, at small scale there may be some exposed carbon, but it still doesn't mater, at cycling temperatures carbon is stable, if coal (carbon) doesn't degrade after tens of millions of years exposure to oil, tar etc., there's no reason the carbon in a bike will

http://www.schunk-sik.com/sixcms/media. ... arbons.pdf

cf is bonded with epoxy resin, exactly which resin will vary, but epoxy is tough, there are chemicals that affect it but a bike isn't likely to get heavy/prolonged exposure to these

there's no reason a chemical compound should be less likely to affect epoxy simply because it's biodegradable, for instance...

http://www.engineeringtoolbox.com/chemi ... d_786.html

...suggests epoxy is less resistant to glucose (biodegradable) than diesel oil (bleaghh)

slap the grease on, it won't hurt cf


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PostPosted: Sat Oct 26, 2013 5:39 pm 
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Joined: Wed Oct 20, 2010 5:56 am
Posts: 397
My Record seatpost came with a warning "NEVER lubricate the seat tube". So from what @sungod says I guess that's not about damaging the carbon, but rather about it becoming loose?


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PostPosted: Sat Oct 26, 2013 6:19 pm 
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Joined: Fri Dec 24, 2010 9:37 pm
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Location: it's raining, it must be uk
is there a clearcoat on the post? use may be cautioning about lubricants wrt to that rather than the underlying cf

for a cf post the only thing i use is some carbon compound, or on a metal post some anti seize, never grease, too slippy

epoxy can absorb water and swell (slightly) and there are various chemicals in cycling use that affect it, hexane for instance, but then hexane is the common solvent in glue for tubs, which is fine on cf rims, similarly acetone is widely accepted as ok for degreasing rims, it's another chemical that affects epoxy, but with such light exposure it's presumably not an issue


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PostPosted: Sun Oct 27, 2013 6:32 am 
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Joined: Thu Oct 13, 2011 5:25 pm
Posts: 169
I've seen in two or three instances a greased carbon fiber seatpost expand/delaminate in the seat tube. It's only happened to 3K weave posts, interestingly enough.

My guess is that grease can interfere with the clear-coat. Really, though, I'm quite unsure about why this happens. Many directions for press-fit components into carbon frames call for grease.


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PostPosted: Sun Oct 27, 2013 7:31 am 
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Joined: Fri Dec 24, 2010 9:37 pm
Posts: 912
Location: it's raining, it must be uk
as i'm up early and it's too dark to go for a ride yet...

i looked at the msds for a carbon assembly compound (the park tools one), it's petroleum grease + plastic grit, my (ax) seatpost has this stuff all over it, gets dragged out and shoved in every time i pack/unpack for travel, plenty of chance to abrade the clearcoat and get at the underlying cf, no sign of any jamming etc.

also dug up some manufacturer quotes saying no grease, one mentioned clearcoat being affected, however a couple of others were saying the resin might be affected and they seen examples of posts delaminate - although if it's in a metal frame that could actually be due to galvanic effects

but as above, some manufacturers say to grease cf, i.e. enve for fitting the crown race, and cf bikes are exposed to oil and grease all day, i've not heard of anyone's frame going weird where the clearcoat got scratched, my rear mech cage certainly hasn't

then i thought, perhaps non-epoxy resins are being used in some components, could certainly be a reason for the differing advice


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PostPosted: Mon Oct 28, 2013 4:48 pm 
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Joined: Tue May 23, 2006 4:33 am
Posts: 975
sungod wrote:
is there a clearcoat on the post? use may be cautioning about lubricants wrt to that rather than the underlying cf

for a cf post the only thing i use is some carbon compound, or on a metal post some anti seize, never grease, too slippy

epoxy can absorb water and swell (slightly) and there are various chemicals in cycling use that affect it, hexane for instance, but then hexane is the common solvent in glue for tubs, which is fine on cf rims, similarly acetone is widely accepted as ok for degreasing rims, it's another chemical that affects epoxy, but with such light exposure it's presumably not an issue


I'd also suspect the clearcoat issue. Some clearcoats are very susceptible to solvents. I've seen some on rims where you don't really notice the damage from solvents but if you look close, the coat is degraded -- it just doesn't affect the basic integrity of the rim. The manufacturers' warnings have to take into account all kinds of mating components from obscure places (like anonymous Chinese brands or small boutique lightweight shops) that don't research the matter properly. In closely mating items, like seat posts, it only takes a very tiny bit of reaction with a clearcoat to cause jamming, not necessarily even visible.

As for acetone, I regularly use it because it flashes off quickly and does remove adhesives including rim cement, but I also have seen it affect rims and other components, at least at the clearcoat. Not that I wouldn't continue to use it, but use it with caution. There are a thousand clearcoats out there and not everybody uses ones that are adequately resistant.


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