# Paste or no Paste on Carbon Steerer



## Robert1 (Mar 27, 2012)

What say you?

I'm always paranoid about over torquing when it comes to carbon and am getting ready to install the stem onto a CF steerer on my new bike. I figured a little tacx carbon paste would be good but I saw this saying it was a bad idea and should be avoided. Thoughts?

The Golden Wrench: A tech bulletin from Trek regarding carbon assembly paste


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## joeyb1000 (Feb 15, 2011)

I use it, and don't see any problem.

On the other hand, this is not a high torque area, and I don't really see it as necessary -- nor do I see it necessary to overtorque your stem bolts.


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## dookie (Oct 1, 2007)

no paste on a steerer. use a torque wrench. done.


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## MerlinAma (Oct 11, 2005)

Robert1 said:


> What say you?
> 
> I'm always paranoid about over torquing when it comes to carbon and am getting ready to install the stem onto a CF steerer on my new bike. I figured a little tacx carbon paste would be good but I saw this saying it was a bad idea and should be avoided. Thoughts?
> 
> The Golden Wrench: A tech bulletin from Trek regarding carbon assembly paste


When you read the reason they give, it seems like it makes sense.

I use carbon paste on my seatpost but haven't seen the need anywhere else. 

PS - I use alloy (not carbon) bars.


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## stevesbike (Jun 3, 2002)

If I'm recalling correctly, Trek has had a bunch of failures with their carbon steerers. First they blamed it on stem designs that had no material between clamping areas (FSA). The carbon paste scenario seems a bit far-fetched - not sure if there are a lot of reported failures of the steerer below the compression ring, but maybe they have some. In any case, as others have said, the area is not a high torque one so could be done without paste. Personally, I've found that 4 Nm is sufficient to clamp a stem to a carbon steerer without paste. DON"T go by the max torque on the stem - find out what the max is for the steerer tube but start lower than that.


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## Camilo (Jun 23, 2007)

I happen to use paste on my CF steerer, and also use a Ritchey Torque key. But really, I, you or anyone, really doesn't have to torque even that high. Like someone said, the stem/steerer connection isn't one that has stress on it at all. The action of steering a front wheel really won't cause that joint to slip even if it's just moderately tightened. But get yourself a Ritchey torque key and use it for our stem and handlebar clamp, also works fairly close on most torque specs for CF seat posts and clamp.

I just read that link, it says:

_The carbon part can be assembled in a clean, dry state. As an alternative, we recommend the following special carbon prep products:
•Tacx carbon assembly compound 
•Fiber Grip™ carbon fi ber assembly gel from Finish Line
_

So what are they telling us not to use? The Tacx and Finish line products are what I've been using?


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## bigbill (Feb 15, 2005)

I don't get the point of carbon paste on a steerer. It's not seeing the weight of a person (seatpost) prying against it. The fork turns with input from the handlebars, the stem/steerer interface doesn't see any tremendous forces other than sheer from an overtorqued stem. No amount of paste will fix improper torque. Proper torque and a little lube on the stem bolts should be all you need.


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## wim (Feb 28, 2005)

Camilo said:


> So what are they telling us not to use? The Tacx and Finish line products are what I've been using?


Yes, don't use any paste at all.

Trek confusingly mentioned the Tacx and Finish Line alternative appearing in their current owner's manual. They will delete that mention in their revised owner's manual.


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## CleavesF (Dec 31, 2007)

No paste on steerer. 

Grease or Paste on seatpost sometimes.


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## AndreyT (Dec 1, 2011)

bigbill said:


> I don't get the point of carbon paste on a steerer. It's not seeing the weight of a person (seatpost) prying against it. The fork turns with input from the handlebars, the stem/steerer interface doesn't see any tremendous forces other than sheer from an overtorqued stem.


While it is true that the stem-steerer joint does not see any serious forces (compared to the seatpost, for example), it is worth mentioning that in the road cycling setup the weight of the rider's upper body is distributed between the seatpost and the bars (i.e. stem). The forces generated on the stem by the weight of the upper body are much greater than the forces needed for turning the fork. Yet for some reason many posters here mention the turning forces, but completely ignore the body weight. The linked article actually mentions the body weight load as increasing under the front braking. 

It is true though that none of these loads are great enough to call for any paste in that junction.


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## Kerry Irons (Feb 25, 2002)

*Forces*



AndreyT said:


> While it is true that the stem-steerer joint does not see any serious forces (compared to the seatpost, for example), it is worth mentioning that in the road cycling setup the weight of the rider's upper body is distributed between the seatpost and the bars (i.e. stem). The forces generated on the stem by the weight of the upper body are much greater than the forces needed for turning the fork. Yet for some reason many posters here mention the turning forces, but completely ignore the body weight. The linked article actually mentions the body weight load as increasing under the front braking.
> 
> It is true though that none of these loads are great enough to call for any paste in that junction.


The real serious force on a stem has not been addressed so far: holding the head set bearing preload. When the front wheel hits a pothole there is major upward force trying to move the stem. People frequently report head sets going out of adjustment because they didn't tighten the stem bolts enough. If they have a slippery situation, you can see the temptation to use assembly paste. 

Whether the abrasion issue is real is open to question. I have never heard what exactly the "grit" in assembly paste is. If it is harder or nearly as hard as the CF composite of the steerer tube then this could be an issue.


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## looigi (Nov 24, 2010)

I could be wrong, but my impression/belief has been that the grit in carbon friction paste is plastic bits that are somewhat softer than the CF composite. In using it, I have yet to see any evidence that it has abraded the CF. This may vary between brands, but using something that would be abrasive would seem like a bad idea in general.


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