Carbon Paste
 

Is it really necessary or only if having slippage problems? Also is it only for carbon to carbon surfaces or would I use it with a carbon bar to alloy stem and then again alloy stem to carbon steerer (even though I have an expansion plug), brifters to carbon bar, etc.

Right now I had thought it was only for seat post to seat tube?

thanks!

I used it on anything where carbon had to be attached to anything else. It allowed me to not tighten too tight so avoiding the danger of damaging the carbon component.

Keep in mind that adjoining surfaces that are clamped together never precisely agree in fit.

Carbon paste therefore has three purposes:
1. Increase resistance to shear creep...increase static friction between surfaces allowing a lower clamp torque for same clamping strength aka PSI.
2. Paste fills voids due to lack of part agreement. Micro-fissures between matching parts are filled thereby increasing clamp surface area. Pasted is incompressible and therefore acts the same as a hard surface when captured in micro voids in mating parts.
3. Prevents stress corrosion if parts aren't the same material.

Its great stuff. I use it where ever carbon parts are present that require clamping...carbon on carbon and carbon on Al...as in the case of carbon handlebar with alloy stem.

Hope that helps.

i even used it on non-carbon seat post. i went crazy.

great feedback thanks folks! I will use appropriately, but not on something like my front derailleur clamp to my painted carbon seat tube right?

Right. I dripped a bit of it onto the bottom bracket shell and didn't notice it until after building and when I wiped it off it had dried and the wiping scratched the paint work. Not cool. Luckily I then knocked over the bike and that little scratch wasn't so important.

I use it on my Al handlebars/stem, but not on seat post. Seat post gets a tiny layer of grease.

You can use it in any mechanical joint where you are looking to increase the friction between the two mating surfaces. It is simply touted as not damaging to carbon.

I hear it's good on toast as well.

ooooo errrr mrs.

I was told you can use grease for more or less the same thing except maybe #1. Bad idea?

Ha Ha - Thanks Man - Brings us back to that reality check paste or not...

ok one last silly question about this stuff... would you use it on the contact point where brifter clamps to bar? the bar is textured

No. You can, but you asked if "I" (you) would use it. "I" would not.

Thanks to this thing I dont even need a torque wrench no more, I never had one anyways :P

No, it's uncessesary. The carbon paste creates the texture necessary. Most bars nowadays are textured where the stem and brifers clamp to.

I'd say yes. Biggest reason is you can end up having to torque things too much to keep them in place. Lots of anecdotal reports of CF seatposts slipping using grease between post and frame, leading to more torque of the seatpost bolt, leading to increase risk of crushing.

Also some manufacturers say not to use grease on their CF parts given a concern that it will eventually makes it way through the clear coat.

Not sure either are big concerns, but given there's an upside to CF paste, and no downside. (it may cost a bit, but a little goes a long way) i'd stick with CF paste.

Funny thing. I tried using CF paste in my carbon seatpost a while back because of constant slipping. Didn't work for some reason. Either I didn't know how to use the stuff or it just wasn't for AL-CF connections.
So nowdays I use toothpaste. Works like a charm. A little bit on the dirty side when disassembling parts, but I never do that anyways so no biggie.

Bikerjp...in response to your question about grease...what Merlin said above.
Carbon paste is a grease of sorts..only without the lubricity.
For the price we pay for our carbon frames, posts, handlebars etc...stick with the stuff designed for it...carbon paste.

There are a few home brew solutions...toothpaste being one. Makes sense that it works...the grit in tooth paste that cleans enamel also helps parts from moving with light clamp force.
I will give you another trick in a pinch. Hairspray works well for keeping a pesky carbon post in place. Install with hairspray wet. When it sets...its very sticky. It like a non invasive adhesive. Also cleans up easily and not hard to get things apart.

The gel coat on some carbon seat posts sometimes is slippery. A tip there is...take 600-1000 grit sandpaper and lightly scuff the clear coat of the post that fits under the seat tube clamp. First be sure to figure out what seat height you like.
With a lightly sanded carbon seat post inside a carbon seat tube + carbon paste and 55 in-lbs or so of clamp torque...seat post shouldn't slip.

campag, do you always use a torque wrench? I was just looking at a simple set from Nashbar, price around $60 but was also thinking I could just be reasonable with clamps, etc.

torque key
 

You can pick up a pre-calibrated 5NM torque key for about 20 bucks. e.g:
http://www.qbike.com/cgi-bin/search....hey+torque+key

That will probably work for most of the parts, except maybe the cranks. Check your parts specifications.

yeah, my ridley front der clamp says 6nm (although I bought a DA clamp on), and some of the others say 4nm so I figured maybe I should just buy a set if necessary.

I used Park Tool SAC-2 Carbon and Alloy Assembly Compound. It's only about $11.00 for a 4-ounce tube, and I can say it really works. My seatpost hasn't slipped since, and I didn't have to torque it as much as before.

Thanks for the info. I didn't have any CF paste so used grease as I was told it would be okay. It's been a couple weeks and I only torqued to spec and so far no issues but I agree there doesn't seem to be any real reason not to use the paste so I'll grab some next chance I get and redo.

+1 - pretty much.

Toothpaste? That is creative. It makes sense.

Robby,
Not always but a lot of the time. The problem is...it is easy to be deceived how much torque is being applied. Since carbon has a smaller elastic zone prior to fracture...albeit with a high yield strength...I generally will use a torque wrench...pretty much always on the seat tube clamp in particular...the seat tube is something I just don't want to crack :) And if undertorqued...seat tubes tend to slip...I weigh 190#. I have good luck at 55 in-lbs and what I use on all my bikes...including Ti.

I am a long time wrench head...built many high performance cars, motorcycles and build my own bikes like many here. I have a pretty calibrated hand...and yet when it comes to carbon fiber in particular, I will generally use a torque wrench. I don't use one on aluminum stem clamp bolts for example...even with carbon handlebar...carbon has great compressive strength...so it depends on the application.

My torque wrenchs of choice are Craftsman...have a few different sizes. Snap on are better if you like the best...go that route...or equivalent.

thanks! With those brands, sounds like I can simply go to Lowe's to pick up one with a set of bits? I was a successful mechanic/parts manager and wheelbuilder back in the mid 80's but jeez equipment has changed so much. Still want to assemble my new bike myself prior to professional fit and steerer tube cutting.

You have one up on me. I am no wheel builder. :)
Good luck with your build.