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· Slightly Opinionated
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When "carbon" and "crack" are heard in the same sentence, I run for the hills.

How do you feel about going face first into the stem, followed by the pavement? Yeah...

Replace.
 

· Adorable Furry Hombre
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Lest you enojy faceplanting....I'd get a torque wrench and a new bar....in that order.
 

· Humanity...or....Vanity?
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I did this to a carbon seat clamp about a year ago.
Never make the same mistake twice.
Purchase torque wrench (learn how to use it) and a new stem.
 

· Bacon!
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Toast!

Please get a new bar. Install in carefully and watch for pinching. I have noticed that mixing 31.7 bars and a 31.8 bar can lead to issues like this.

I found this out with my Syntace CF bar and a Deda stem.

Because 31.7 and 31.8 stem are not true sizes (round up or down) there can be times where the bar is slightly too big for the clamp. Now it's sooo close where they are interchangeable. But if you are not careful and tighten the lower or upper part unevenly, you can pinch the bar, which will lead to this cracking issue.

I though my Syntace bar just failed and it was replaced under warranty. But after going over with the installation and noticing I almost did the same thing twice I realized this. Syntace tech said it cold be an issue as well as a few others mechs.

You have to REALLY over tighten your bolts to crack a CF bar if the install was correct and the fit well with each other. Get a torque wrench or learn to use a Y-tool Allen wrench to achieve the min torque required.

Also look at the bars recommended torque. Deda say 8NM for their stems, but most bars say max of 5NM. Follow the bars torque specs or just snug them up enough to keep them for rotating.

My 3T bars say 5NM and I am using them with a 8NM Deda stem. 4.5NM is holding them more than enough..
 

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MerlinAma said:
Get a lighter, relatively inexpensive alloy bar and consider this a lesson learned.

You don't need to buy everything carbon "they" are selling.
Most alloy bars are not lighter nor stronger.
 

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DIRT BOY said:
Most alloy bars are not lighter nor stronger.
But alloy's do not crack. All alloys have a certain amount of flex in the walls of the tube, which carbon doesn't have. This allows you a little more leeway on the torque ratings.

Alloys are actually stronger. Carbon cracks as a feature of its stiffness. The alloys tend to absorb force and transmit it across it's area much better than carbon.

I doubt very seriously if anyone can feel the difference between the weight of an alloy bar and carbon.
 

· Number 2 on the course.
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Amsmoore said:
But alloy's do not crack. All alloys have a certain amount of flex in the walls of the tube, which carbon doesn't have. This allows you a little more leeway on the torque ratings.

Alloys are actually stronger. Carbon cracks as a feature of its stiffness. The alloys tend to absorb force and transmit it across it's area much better than carbon.
Wrong on every count.
 

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Discussion Starter · #12 ·
thanks to all for your replies. Yes it is time to buy a

torque wrench and I will be more careful. No doubt that it gets expensive buying and breaking this stuff. A lesson learned.
thanks again,
 

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PeanutButterBreath said:
Wrong on every count.
Do elaborate.

For the purpose most used in cycling, alloy bars are stronger and more durable than carbon.

Can you crack cryoed 300M? Sure. But thats not whats in our products.

There is no benefit to carbon bars, except for a couple grams.

What do the pros ride? I'll give you a hint, its not carbon.
 

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Amsmoore What do the pros ride? I'll give you a hint said:
I would not race carbon either. Why? Carbon does fail catastrophic manner. Alumin will give warning usally. They don't have time in the middle of a GT too see if their CF bars cracked in any type of fall. I can.

That's all. I have had aluminum bars bend form a bike falling over. Not my CF bars. CF can be made stronger and lighter. But it's HOW they fail that keeps pro riders riding aliminum. Secondly, what a pro uses has LITTLE to do with what I choose.

But yet these pros will ride a CF frame and not worry about that failing right? :rolleyes:
 

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DIRT BOY said:
I would not race carbon either. Why? Carbon does fail catastrophic manner. Alumin will give warning usally. They don't have time in the middle of a GT too see if their CF bars cracked in any type of fall. I can.

That's all. I have had aluminum bars bend form a bike falling over. Not my CF bars. CF can be made stronger and lighter. But it's HOW they fail that keeps pro riders riding aliminum. Secondly, what a pro uses has LITTLE to do with what I choose.

But yet these pros will ride a CF frame and not worry about that failing right? :rolleyes:
You might want to check your bars, then. That's why alu. is popular. if it bends, you can see it. If you drop carbon bars, you have to pull the tape and the headplate to check.

I find it hard to believe that you bent aluminum bars from dropping a bike. If by "falling over" you meant "dumped into a ditch at 30mph" sure but not from a waist level fall.
 

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Amsmoore said:
You might want to check your bars, then. That's why alu. is popular. if it bends, you can see it. If you drop carbon bars, you have to pull the tape and the headplate to check.

I find it hard to believe that you bent aluminum bars from dropping a bike. If by "falling over" you meant "dumped into a ditch at 30mph" sure but not from a waist level fall.
I have and do check my bars.

Nope, it feel form a strong wind and hit a coner of a wall. Bent them ever so slighty. Some cheap Bontrager bars.
 

· Number 2 on the course.
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Amsmoore said:
Do elaborate.
You generalized contrast of CF and Al is based on flawed assertions about the material properties and failure modes of the two materials.

The following statements are false:

Amsmoore said:
But alloy's do not crack.
False. Alloys can and do crack.

Amsmoore said:
All alloys have a certain amount of flex in the walls of the tube, which carbon doesn't have.
False, unless maybe you are describing a hypothetical pure carbon handlebar. Carbon fiber handlebars flex.

Amsmoore said:
This allows you a little more leeway on the torque ratings.
Over-torqueing either can cause premature failure.

Amsmoore said:
Alloys are actually stronger.
Pretty huge generalization, but if we narrow it down to bicycle parts, this is definitely false, unless by "stronger" you simply mean tougher.

Amsmoore said:
Carbon cracks as a feature of its stiffness.
Its a truism that stiff materials are more likely to crack (better to bend like th willow), but carbon fiber is not necessarily stiffer than Al. Moreover, since carbon fiber does not have the limited fatigue life that Al does, it can go far longer without cracking.

Amsmoore said:
The alloys tend to absorb force and transmit it across it's area much better than carbon.
Nope.
 
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