Carbon paste - yea ...
 

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Carbon paste - yea or nay?

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 PJay
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I find myself in possession of my very first all carbon fork and a nice set of carbon drop handlebars. I'm aware that carbon isn't that resilient against crushing forces and that it's possible to use carbon assembly paste to increase grip, allowing lower torque. In the great mire of mis-information that is YouTube, I came across someone claiming that as carbon paste is often made with glass dust/beads it could actually abrade carbon components (although how that happens in a static interface I don't know).

The two non-opposing stem clamp bolts for the Thomson stem I'll be using have torque ratings of 5.5Nm and Ragley are quite happy that this will be fine for the steerer. Similarly the faceplate bolts are rated at 4Nm and Easton say this is fine.

So, since all the torque values of all the components are acceptable, do I just set everything up dry, do I set them up at full torque with a bit of paste for extra oomph, or do I assume that less torque is better where carbon is concerned, use paste but go lower torque?

If it's lower torque, is it possible to quantify the effect of the paste? In other words, if I use paste can I reduce the torque from, say, 5.5Nm to 4.5Nm and be confident that the effect is the same, or is it a bit more quessworky? I don't wont to find out that I've gone too low when the bars come off in my hand as I'm riding.


 
Posted : 09/12/2023 8:30 am
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I use carbon assembly paste if something is torqued correctly and is still slipping, the main thing being on matchmaker clamps to stop them slipping when using either the dropper post lever or the shifter.


 
Posted : 09/12/2023 8:38 am
nickc and nickc reacted
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You don't necessarily need it, I've found Thomson stems to be machined to very tight tolerances. I use it by default for dropper posts where you want the seat clamp to be as loose as possible. I usually put a smidge on the stem face plate but not on the steerer.


 
Posted : 09/12/2023 8:45 am
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What Kramer said. Have heard the same from actual mechanics as well.


 
Posted : 09/12/2023 8:55 am
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A smidge on the face plate but be careful, Trek and some other companies advised against it on the steerer/stem clamp some years ago as it can migrate down to the head tube/bearing interface and in the case of a carbon steerer, cause damage there. I’d use it on a seat post as a clamping aid but also to help removal as carbon/carbon can also seize together. Hope this helps.


 
Posted : 09/12/2023 9:10 am
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Same as @Kramer, torque everything up to spec and if it moves use carbon paste. I wouldn't use carbon paste to aim for lower torque values. Presuming you're not honking on the bars like Philipsen going for the line, the bars aren't going to move. 


 
Posted : 09/12/2023 9:16 am

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