# Is carbon bar supposed to dent a bit when installed?



## Muscleflex (Nov 23, 2012)

Hi all - apologies for the newbie question.
I just got a carbon flat bar. I installed it tonight. It says max of 6Nm so I used 5.5Nm on my new clicky torque wrench.
However, I noticed it kinda dented where the pressure point is of the stem.....
Is this normal? Is it cracked?
I have installed it back anyway and took it out for a ride in the park - locked the suspension and banged on the bars hard a few times and did some rough wheelies and dropped wheel down hard to see if there will be any play or something but didn't feel anything.


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## moefosho (Apr 30, 2013)

Did you go by the specifications on the Carbon bars or the specs on the stem? No, it shouldn't dent. It may be garbage now...


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## Muscleflex (Nov 23, 2012)

It says 6Nm on the bar


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## Harold (Dec 23, 2003)

that's not a torque problem. that's an uneven clamping surface problem. and yes, that's a problem for your bars. This is why I don't use carbon bars. you have to be real nitpicky about clamping surfaces, filing off edges and being super diligent about the WAY you tighten the stem faceplate to avoid compromising the bar the way you did there.


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## AZ (Apr 14, 2009)

That looks damaged to me. You may wish to have a qualified person give their assessment.


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## kapusta (Jan 17, 2004)

Carbon bars often have a grippy coating around where the stem clamps and it is a little bit pliable. What you are seeing may just be that softer coating getting a little smooshed.

However, it is hard to tell on the internet. I would have a shop look at it to be sure.


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## Muscleflex (Nov 23, 2012)

Thanks - I've put it back on the bike... but I used 5Nm this time... I've contacted the place I got it from to ask..

by the way, how am I supposed to install it? Was I supposed to put heli tape or something before I put in the stem? My stem is smooth and I made sure all sides were the same when I was tightening with my torque wrench


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## GTscoob (Apr 27, 2009)

Muscleflex said:


> by the way, how am I supposed to install it? Was I supposed to put heli tape or something before I put in the stem? My stem is smooth and I made sure all sides were the same when I was tightening with my torque wrench


Maybe get a better stem that has more of a wrap around the bars? A lot of CF friendly stems are coming out with the most minimal of faceplate gaps and increased bar wrap rather than having the faceplate cover 50% of the bar and the stem the other 50%.


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## kapusta (Jan 17, 2004)

Muscleflex said:


> Thanks - I've put it back on the bike... but I used 5Nm this time... I've contacted the place I got it from to ask..
> 
> by the way, how am I supposed to install it? Was I supposed to put heli tape or something before I put in the stem? My stem is smooth and I made sure all sides were the same when I was tightening with my torque wrench


Despite what I said above, I would not ride it unless you are sure it is not a dent or crack in the CF itself.


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## kapusta (Jan 17, 2004)

GTscoob said:


> Maybe get a better stem that has more of a wrap around the bars? A lot of CF friendly stems are coming out with the most minimal of faceplate gaps and increased bar wrap rather than having the faceplate cover 50% of the bar and the stem the other 50%.


Got a link to one of these? I'm trying to figure out how, if the clamp diameter matches the bar, you can have it wrap more than half way around the bar and still get the bar into the clamp. I know you could do that on older stems, but they were a bit more flexible, allowing you to slide the bar in from the side.


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## Muscleflex (Nov 23, 2012)

bike is the cannondale flash. the stem is an integrated something... don't know if I can use a different stem with the lefty fork?


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## GTscoob (Apr 27, 2009)

Ritchey has 260 degree wrap on their new WCS stems:
Road Bike Stems - Ritchey Road Bicycle Stems

I'm pretty sure Raceface stems I've had in the past have had more than 180 degrees of wrap. Thomson stems always clamp down with no gap so I'd imagine that makes for very uniform clamping.


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## manmythlegend (May 21, 2012)

As many horror stories that go around dont ride it until someone qualified can tell you its safe or normal. Carbon seems to be a very scary when failing material.


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## Muscleflex (Nov 23, 2012)

Can anyone tell me what Nm you guys use on your carbon bars? Did I got too much by using near 6Nm?


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## tnrider (Nov 5, 2009)

The torque should be determined by the stem. It may be written on the stem, or you may have to look it up.


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## eatdrinkride (Jun 15, 2005)

Muscleflex said:


> It says 6Nm on the bar [/QUOTE
> 
> It says 6nm on the stem.
> 
> ...


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## eatdrinkride (Jun 15, 2005)

tnrider said:


> The torque should be determined by the stem. It may be written on the stem, or you may have to look it up.


Completely false... 100 percent inaccurate advice.. Not trying to be a prick just trying to make this clear

The stem has no idea what type of handlebar you are installing. Steel, aluminum, carbon fiber, balsa wood. Each of these materials would require a different clamping force independent of the stem bolt maximum torque value.


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## moefosho (Apr 30, 2013)

Muscleflex said:


> Can anyone tell me what Nm you guys use on your carbon bars? Did I got too much by using near 6Nm?


6 Nm seems like it is too much. I usually put mine at 1.75Nm with carbon paste and see if it holds. If it does, great. If not I up it until it doesnt slip. My bars right now are just over 2Nm and are perfectly tight.


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## mbco1975 (Feb 28, 2012)

eatdrinkride said:


> Completely false... 100 percent inaccurate advice.. Not trying to be a prick just trying to make this clear
> 
> The stem has no idea what type of handlebar you are installing. Steel, aluminum, carbon fiber, balsa wood. Each of these materials would require a different clamping force independent of the stem bolt maximum torque value.


Well my Easton EC70 handlebars came with instructions saying torque to the spec of the stem. My Stem is a syntace f109 which says up to 6nm, so I torque to 5 and have no issues in the last 9 months since installing.


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## eatdrinkride (Jun 15, 2005)

mbco1975 said:


> Well my Easton EC70 handlebars came with instructions saying torque to the spec of the stem.


Well my apologies then. I can't believe it actually says that maybe they're referring to the aluminum bar. At any rate it makes no sense as those values are bolt torque specifications values. And really have nothing to do with the clamping force needed of the handlebar. I think its just lazy instructions. 6nm is way too much for any carbon fiber bar I've owned. The idea really is too snugg it up just enough that they don't move. Around 2 to 3 mm.


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## tnrider (Nov 5, 2009)

eatdrinkride said:


> Completely false... 100 percent inaccurate advice.. Not trying to be a prick just trying to make this clear
> 
> The stem has no idea what type of handlebar you are installing. Steel, aluminum, carbon fiber, balsa wood. Each of these materials would require a different clamping force independent of the stem bolt maximum torque value.


Just checked the manual again for my s-works bar, it says to use the torque settings for the stem. I have installed all of my carbon bars this way, my LBS has also told me to use the torque values from the stem. I am guessing that I am not more than 50 percent incorrect.

Sent from my SCH-I510 using Tapatalk 2


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## Radamus (Feb 18, 2008)

I find it hard to believe that the bar, at the center of it's largest diameter, the heartbeat of it's demand, is so whimpy as to crush like an egg from a possible 2x torque'in. I ponder, How much torque might I be applying throwing my body weight into it as I'm grabbing for dear life- Like mountain biking is sometimes? If I had to guess, it's not broken. Hope that turns out to be the case for you regardless. I agree with everyone else, better to have it checked than to guess and get hurt.


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## bob13bob (Jun 22, 2009)

Echoing above, is it just smooshy material?


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## Muscleflex (Nov 23, 2012)

eatdrinkride said:


> It says 6nm on the stem.
> 
> Have you read the instructions from FSA on the installation of your handlebar? In the instructions it clearly states that the torque value stamped on your stem is the maximum allowable torque before one might expect bolt failure. It has nothing to do with the torque spec for your handlebar. In the manual it also states that final torque value for your carbon bar should be about 2 to 3 Newton meters. It seems you have torqued the bar two to three times over the recommended amount.
> 
> ...


yeah that's my bar... and no, I didn't read it. I just went straight away to install it remembering not to go over the 6Nm torque...
so will 3 or 4 nm be enough on the bar (for next time?)


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## Muscleflex (Nov 23, 2012)

Thanks all. I'll get it checked. I won't be using the bike for trails... until I get it checked.


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## Muscleflex (Nov 23, 2012)

by the way, this is what it looked like before i installed it:


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## Blk02 (Apr 15, 2006)

I tighten mine to 5nm. FSA recommends 4-5nm and they specify to never exceed 9nm on their website. I think 6nm is still a safe number because it is stamped on all the FSA stems I have bought and it does not say max torque next to 6nm on the stem. However if I bought a handlebar and it said max of 6nm I would not get close to that number. I would stay in the 4-5nm range.

Handlebars: Torque Settings


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## Blk02 (Apr 15, 2006)

According to the FSA website 2-3nm is for brake levers and shifters not the stem or steerer clamp bolts. In another section of the FSA site is specifies 5-6nm for the stem clamp bolts as being adequate "Most FSA stems can be tightened adequately with 5-6Nm torque". I would not use 2nm on stem clamp bolts ever because that is just too light. I would also check your torque wrench. If you are use a $30.00 wrench then you could be off by 1nm. It is best to buy a torque wrench above the $100 mark and get a calibration certificate. However from the looks of the mark it seems like the fit between the stem and handlebar was not correct.

FAQ: STEMS: TORQUE SETTINGS - FULL SPEED AHEAD COMPONENTS

4. Check Brake Lever and Shifter clamp areas for burrs, chips, or sharp edges that may dig into handlebar. Remove burrs, chips, or sharp edges with sandpaper before installing. Install brake lever and shifter onto handlebar.
Do NOT use twisting motion. Tighten brake lever and shifter band clamp to minimum torque necessary to secure component. Usually 20-30 kgf.cm / 2-3 Nm / 18-26 in.lbs.



eatdrinkride said:


> Muscleflex said:
> 
> 
> > It says 6Nm on the bar [/QUOTE
> ...


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## Muscleflex (Nov 23, 2012)

thanks. well i'm still using this handlebar.. just for commuting to work. I keep checking it and does not seem to have any play. when I get a chance, I shall take it to the shop I got it from and will ask.


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## zephxiii (Aug 12, 2011)

To me that looks like the protective layer in the clamp area of the handlebar is just smooshed. When you are tightening the clamps down they can grab that protective layer, stretch it, and bunch it up in the gap area as it closes. That's what it looks like to me but I would inspect the carbon underneath the protective layer. Neither of my carbon bars have that protective layer in the clamp area interestingly.


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## squidsauce (May 19, 2014)

Sorry to resurrect this thread, but I just had a similar problem with my enve road bars.
I was wondering if you ever got a chance to check with your bikeshop if the marks were ok or not?


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