Cracked My Carbon Handlebars

[Frank Draper]

Yesterday I adjusted my Bontrager XXX Lite VR handlebars to angle the hoods slightly more upward. I was using a brand new Mariposo torque wrench and the Bontrager factory spec's of 7.9 nm (my wrench was set at 7.5 nm), and adjusting using a star pattern. Well, three of the four stem bolts on the Bontrager stem all clicked at the 7.5 setting with no problem. The bottom right bolt (four in a square) did not and I heard a sickening crunch as my handlebars spilt at the bottom right bolt. Needless to say I am very angry. I have adjusted the bars maybe 3 other times since I got the bike in mid-Jan. of this year always using the same torque wrench and no problems. So, it's off to my LBS to see what happened and order a new handlebar ($400!!). The only thing I can figure is that the bars may have had a slight crack in them and would not take the torque on that bolt. I have never crashed, it hasn't even fallen over and always treat it with kid gloves. The bars have a 5 year warranty but I have no idea if my situation will be covered.

Any ideas about the possible cause?

[flux]

[QUOTE=

Any ideas about the possible cause?[/QUOTE]

You install carbon bars once at torque then leave them alone. These things aren't mean to be torqued-untorqued repeatedly.

None the less I'm sure Bontrager will give you a full refund/replacement.

[Dave]

Did you tighten each bolt all the way from loose to fully tight in one step? I always tighten by hand, using a crossing pattern, but go around at least three times. I've never used a torque wrench on a stem, or any other M5 bolt. A lower torque of only 5Nm is often recommended on the stem.

Repeated removal an reinstallation should not be a problem. The bars were probably crap to start with. I've owned several Easton and FSA bars and never had any problems swapping the bars between bikes and changing stem lengths on occasion. All of my bars have survived several reinstallations and plenty of angle adjustments.

Perhaps you have some warranty coverage. Easton carbon bars are warranted for life to the original owner with proof of purchase. Of course no bar has a crash warranty.

[weiwentg]

You install carbon bars once at torque then leave them alone. These things aren't mean to be torqued-untorqued repeatedly.



:confused:

so, are there carbon bikes that you ride 100 miles and then leave them alone? are there carbon handlebars where you shouldn't stand up to pedal, for fear of putting too much torque on the bars? if the carbon bars can't stand being torqued to spec a few times, how are they going to make it through a ride?

[oldguy00]

Stick to aluminum for handlebars!! Hard to beat a Deda Newton in terms of price, quality and weight.
Probably not the response you were looking for..

[reblaus]

7.5 Nm...oh my God..... :no:

....Carbon Montagehttp://www.raddiscount.de/images/shop/P03943_BILD1GROSS.jpg and a Torque of 3NM max....

[StefanZ]

Sorry to hear about the carbon bars breaking. Due to the issues of installing and longevity, I have shifted away from carbon components and enjoy the trusted aluminium stems, bars and seatposts (not that they can't fail, but well made components will last a very long time, and the weight is often comparable to carbon).
My 2 cents

[flux]

:confused:

so, are there carbon bikes that you ride 100 miles and then leave them alone? are there carbon handlebars where you shouldn't stand up to pedal, for fear of putting too much torque on the bars? if the carbon bars can't stand being torqued to spec a few times, how are they going to make it through a ride?

I don't think you understood the message I was trying to convey.

A competent tech knows better than to torque-untorque-retorque repeatedly carbon clamping areas. It's like playing with fire. This has nothing to do with the stresses your body and general riding motions place on a carbon bar (or any other carbon component for that matter) when riding. I am talking about clamping surfaces, torque specs and technical competency. This is why some people just shouldn't work on their own bikes regardless of how simple the task (no offense to the OP).

[J.Greene]

Stick to aluminum for handlebars!! Hard to beat a Deda Newton in terms of price, quality and weight.
Probably not the response you were looking for..

Yes, hard to beat those newton bars, but the oval bars and matching stem from my favorite stockist does it everytime.

JG

[Frank Draper]

7.5 Nm...oh my God..... :no:

....Carbon Montagehttp://www.raddiscount.de/images/shop/P03943_BILD1GROSS.jpg and a Torque of 3NM max....
If what you write is true, then why would the Bontrager factory rep send me in writing to torque no more than 7.9 nm.? And yes I used a star pattern from beginning to cracked and went around from the start to finish which took about12-15 rounds.

[sspielman]

As Flux has said, one of the most dangerous times for carbon components is during building process, in the repair stand....In any event, the stem clamp may be one area for failure with carbon bars, but the one that gives me WAY more reservations is the LEVER CLAMP AREA.....There are stems that are carfully designed to be used with carbon bars, but the lever clamps are generic, thin, and the attachment bolts can be difficult or impossible to access with a torque wrench...

[jemoryl]

I don't think you understood the message I was trying to convey.

A competent tech knows better than to torque-untorque-retorque repeatedly carbon clamping areas. It's like playing with fire. This has nothing to do with the stresses your body and general riding motions place on a carbon bar (or any other carbon component for that matter) when riding. I am talking about clamping surfaces, torque specs and technical competency. This is why some people just shouldn't work on their own bikes regardless of how simple the task (no offense to the OP).

Yet another reason to stay away from carbon bars, IMO.

[Squint]

Mechanical torque wrenches aren't very accurate which is why I use an electronic one. This isn't the first time I've heard of someone breaking a bike part despite using a torque wrench. In those stories, a mechanical torque wrench is always involved.

[Blue Jays]

Unfortunate narratives like this are making me regret the purchase of my Deda Campione carbon fiber bars more and more! Perhaps it's simply not an ideal material for handlebars. :(

[zap]

Torque value stated by the op is not that unusual. But, on all my carbon bars, I use 5-5.5 nm and use some friction material between stem and h/bar. I've made several fine adjustments to hbar angle over the years and all is well.

Carbon parts have served me well for two decades. However, I have seen some new carbon bars that had inclusions that appeared to deform the carbon layup. Those bars went back to the manufacturer.

[Frank Draper]

I don't think you understood the message I was trying to convey.

A competent tech knows better than to torque-untorque-retorque repeatedly carbon clamping areas. It's like playing with fire. This has nothing to do with the stresses your body and general riding motions place on a carbon bar (or any other carbon component for that matter) when riding. I am talking about clamping surfaces, torque specs and technical competency. This is why some people just shouldn't work on their own bikes regardless of how simple the task (no offense to the OP).

So, how can someone change the position of the handlebars without untorque-torque? While I do appreciate your comments I still question why when using manufactures specs and directions will the bar crack. I do not consider 3 times in a three month period an excessive amount in order to repostion for a change in riding position. Also, I am a graduate of Barnett's Bicycle Institute and dare say, from my experience, that quite a few "bicycle shop mechanics" don't have the knowledge and skills necessary to do a competent job. I'm not an expert but consider myself someone with better than average mechanical skills.

Again, thanks for the comments but I find myself even more confused than before.

[J.Greene]

Unfortunate narratives like this are making me regret the purchase of my Deda Campione carbon fiber bars more and more! Perhaps it's simply not an ideal material for handlebars. :(

Maybe, but consider this....on any really light bar there is a greater chance of a failure. Inspect these parts often.

JG

[reblaus]

Mechanical torque wrenches aren't very accurate which is why I use an electronic one.


:confused: i'm sorry, but if you set a electronic torque wrench to the wrong torque....it cracks...simple and analog.... :D

[swoop]

carbon bars are great. i've done hundreds of races on them and tens of thousands of miles without incident.

abstracting and generalizing from one failure is lame.

all materials and all parts have incidents of failure. the lighter the part the more you have to use and install correctly.
they will warranty it. hopefully he's not tightening the bolts from zero to spec one at a time and wondering why its not working.

next please.

[Frank Draper]

carbon bars are great. i've done hundreds of races on them and tens of thousands of miles without incident.

abstracting and generalizing from one failure is lame.

all materials and all parts have incidents of failure. the lighter the part the more you have to use and install correctly.
they will warranty it. hopefully he's not tightening the bolts from zero to spec one at a time and wondering why its not working.

next please.

Thanks Swoop,
No, I'm not tightening the bolts from zero to spec one at a time. I am using the recommeded alternating star pattern and from loose to torque is between about 10 to 12 half turns. Maybe there is something that I am not doing correctly, but I follow the instructions exactly as written.

[swoop]

Thanks Swoop,
No, I'm not tightening the bolts from zero to spec one at a time. I am using the recommeded alternating star pattern and from loose to torque is between about 10 to 12 half turns. Maybe there is something that I am not doing correctly, but I follow the instructions exactly as written.

you got some bad bars or there's a burr on the stem or face plate.

i've seen and know many guys on these bars. one of which is just a few clicks shy of ape. no issues.

[goonster]

A competent tech knows better than to torque-untorque-retorque repeatedly carbon clamping areas. It's like playing with fire.

Why? :confused:

Please explain, and please do not hesitate to go into detail.

[swoop]

Why? :confused:

Please explain, and please do not hesitate to go into detail.

all of these parts fail in cycles of stress. even your seatpost bolt will fail if tightened and loosened enough times.

[pdxmech13]

Frank, that is a good bar and stuff happens even with quality equipment/tools. I think that the torque measurement was a little high even though that was what you were told. Most M5 bolts with a 4mm hex head need no more than 6nm. Anywho Trek will take care of you. Don't forget that most manufacturers (bontrager included) offer crash/damage replacement on their carbon offerrings.

[goonster]

parts fail in cycles of stress.

Yes, I remember them teaching us that in engineering school.

But normally the service life of a part is measured in tens or hundreds of thousands of cycles of elastic deformation.

Flax is asking us to believe that clamping a handlebar more than once is somehow foolish and unsafe. No technically competent person would do this, he says.

Are you really suggesting that installing the bar once is safe, but doing so two or three or ten times constitutes unsafely exceeding the number of permissible stress cycles?

[flux]

Yes, I remember them teaching us that in engineering school.

But normally the service life of a part is measured in tens or hundreds of thousands of cycles of elastic deformation.

Flax is asking us to believe that clamping a handlebar more than once is somehow foolish and unsafe. No technically competent person would do this, he says.

Are you really suggesting that installing the bar once is safe, but doing so two or three or ten times constitutes unsafely exceeding the number of permissible stress cycles?

It's "flux" not "flax".

I am not a materials engineer and I don't really feel like giving you my entire background and experience level on the matter. I wouldn't post on this thread unless I felt merited. I would also like to say that I did not intend to offend anyone. I simply stated and will continue to state that carbon parts are not designed to be clamped-unclamped-then reclamped repeatedly.

You torque about halfway to spec or enough that the bar doesn't slide around, you decide where you would like the bar to be for certain, you then torque to spec and leave it alone.

In my opinion there are a number of things that could have led to the demise of this bar but I honestly doubt a company as established and respected as Bontrager would "let one slip through the cracks". (pun)

Good Luck.

[Big Dan]

Believe..

[Tom]

Is a new torque wrench? Was it calibrated? I don't know if it's necessary but I happened to come into possession of a really nice one that comes with a certain three-letter computer manufacturer's equipment and they go on about how it was calibrated at the factory so there's no need for me to do it. (It's a great completely over-engineered tool, that wrench. I love it. There's absolutely no mistaking when that baby says it's where it wants to be.)

I'm also mildly surprised at the torque value. I just put on an aluminum Ritchey stem on an aluminum set of bars and they said to max out at five.

[goonster]

It's "flux" not "flax".


Sorry. I'm a doof.

I simply stated and will continue to state that carbon parts are not designed to be clamped-unclamped-then reclamped repeatedly.

I can agree with this, if only because the act of doing this introduces risks of scratching, clamping improperly or uneven loading. It should be done very carefully and not repeated frivolously.

Noone is offended, but I think it's important to understand what is going on here, as it relates to the safe use of equipment. The reason I spoke up is that if the OP installed his bars carefully, and torqued to Bontrager's specs, he shouldn't feel that he contributed to this failure.

[Lifelover]

... So, it's off to my LBS to see what happened and order a new handlebar ($400!!). .


Hokey Mokey!

[Gothard]

That we have to dirve ourselves crazy with precision instruments (which in themselves cost a fortune), and then wonder while bombong down at 40+ whether the torque wrench was within specs, and that there were no shards of alloy that could have dug into the 400$ :eek: handlebars is a testament to the failure of cycling as a means of recreation.

Last thing I want to think about when coming down one of my mountain passes is what could happen in case of a failure.

Are we all sure that this is why we are into cycling?

[goonster]

Last thing I want to think about when coming down one of my mountain passes is what could happen in case of a failure.

Why would you worry?

For $400 you get excellent warranty service! :banana:

[sspielman]

Last thing I want to think about when coming down one of my mountain passes is what could happen in case of a failure.


All of these modern materials are well proven in other -such as aerospace- applications...Take the Space Shuttle for example....Oh..Never mind.....

[sg8357]

Believe..

To test composites you need a hammer.

http://www.wichitech.com/rd3taptammer.html

Battery operated for use on the team car after crashes.

[Kevan]

I certainly have nothing scientific to support the reasoning, but I have to think that multiple clampings and the compression and expansion that follows within the bar itself could be a contributing factor to a failure. Bars are most commonly subjected to push/pulling type torque which is a different strain than compression.

Just sticking my nose into something I have little knowledge about.

[Gothard]

In fact, my reaction is a knee-jerk.
I am pretty sure these bars are plenty strong enough, usually.
Still, the retro-grouch and teeth-in-my-mouth-not-on-the-road chicken in me likes the heavy NOS alloy Cinellis and 3Ts that abound for sale.

Purely subjective.

EDIT: if tightening and loosening a bolt *3 TIMES* is a cause for failure, then I want my money back.

[Kevan]

a nearly 7 year old Easton CF bar out of fear. Now removed and looking at it, I think it could have stayed on a couple more years.

[swoop]

ALL MATERIALS FAIL PREDICTABLY UNDER THE RIGHT CIRCUMSTANCES.

if you like light parts you have to speak the light part language. they take a little more vigilance on the part of the user especially during assembly. i don't think there is a higher incidence of failure of components between light and standard parts.. but rather properly manufactured and properly installed and maintained parts tend not to fail under normal use and do fail when improperly maintained, installed, and misused.

for all we know there's a big burr on the clamp, or the clamp is poorly machined or not for use with carbon bars, or there was a void in the lay up, or they were assembled to the wrong torque setting. i've seen carbon and aluminum parts fail in equal measure and both screamed with symptoms that were ignored prior to failure.. and only noticed in retrospect.

[stevep]

aluminum bars.

[R2D2]

I certainly have nothing scientific to support the reasoning, but I have to think that multiple clampings and the compression and expansion that follows within the bar itself could be a contributing factor to a failure. Bars are most commonly subjected to push/pulling type torque which is a different strain than compression.

Just sticking my nose into something I have little knowledge about.

It's possible that there was a stress point in the previous placement of the bars. Then when they were rotated a new stress point was introduced.
Thus weaking a larger area.
Happens on aluminum bars too.

[soulspinner]

aluminum bars.

+1-must have been an imperfect surface inside the stem? Glad you saw it instead of pavement surfin...

[Peter P.]

You don't have enough data points to come to any solid conclusion as to what just happened to your carbon bars. I wouldn't complain. But if $400 is considered a lot by you to replace a pair of handlebars, then it's time to reconsider your choice in handlebars.

If you have the receipt and the bars are still under warranty, the manufacturer really has no recourse except to replace them because they CAN'T prove you torqued them improperly. I'm not trying to talk legalese here; it's just that they'll have to take your word on it and besides, it would be good customer relations.

So what happened? Let's assume you torqued them per the manufacturer's instructions. Then maybe you just had a bad bar. It's my opinion that the market STILL hasn't figured out how to reliably manufacture carbon bars yet, so we're going to see an inordinately high number of failures vs. aluminum bars for several more years. Of course, if the stem is NOT from the same manufacturer, they could fall back on that as an excuse, but I dont think it's valid unless it's in print in there literature.

[Frank Draper]

Just returned from my LBS. I explained to them exactly how I loosened and retorqued my stem/bars. I had not touched the bolts since the bars cracked and asked the lead mechanic to use his torque wrench to check the torque. He very carefully loosened a bolt then retorqued it with his torque wrench until all three were done. Every one of them clicked at 7.5nm. He said that I had done it the same way that he and the other mechanics do it. So, I am relieved that it wasn't anything that I had done incorrectly. He did not take off the handlebar. Just said that he would file for warranty replacement from Bontrager. So, I don't know if there may have been a burr on the clamp or if it was poorly machined. I assume they will look at that when the new bar is received.

In regard to the stem, it is the Bontrager Race XXX Lite Carbon that is spec'd for the bars that come stock on the bike, a 2008 Lemond TeTe de Course.

And yes it is a brand new Italian made Mariposa(www.effettomariposa.com) that is supposedly good for 5,000 clicks and then return to the company for recalibration.

I appreciate everyones response and hopefully something will be0 learned from my experience. It could have been any number of things that caused the failure and most of you have definitely stated some of the possible causes. If it is determined what caused the bars to crack then I will include the findings in a later thread. And, I will not torque the new bars to the specified 7.9nm, not even 7.5 as I did. Probably, using a torque wrench set at 4nm for maximum tightness and tighten only until I can't move the bars with the pressure of my hands and arms. Geez, we're regressing to BTW (before torque wrenches).

[Dave]

While you're wating for those new bars, you might want to practice tightening bolts to about 5Nm. Then you can actually make an adjustment out on the road without fear. I'll never own a torque wrench to tighten M5 bolts.

FWIW, the Ritchey 4-axis is a great stem if the available angles suit you. I've never had a bar slip after tightening the bolts with a short handled or Y style wrench.

[swoop]

that anti slip paste is the shiznit too.

[BdaGhisallo]

Get one of Ritchey's Torqkeys. They are preset for 5 nm.

[DarrenCT]

Get one of Ritchey's Torqkeys. They are preset for 5 nm.

bingo

this thing rules