Originally Posted by abstractform20 (Post 13489736)

i think the reason many of us doubt the ability of the helping friend is because he continued to keep wrenching after hearing cracking sounds.

would stopping after cracking fix any issue with the bars? no.

would continuing to wrench after hearing cracking in carbon bars fix anything? no.

it is irrational and counterproductive to continue the process once failure has occurred.

also, i found it weird that the friends mentions thinking that the cracking might have been the sound of the bolts threading in.

if the integrity of the bars was compromised, but was not visible from the surface, then the safety of the rider would be at risk.

if i worked on someone's bike and heard cracking or any other breaking noise, i would inform the person that the bike may not be suitable to ride.

so while we do not have proof that the failure was due to the mechanic or the handlebars, there are many of us who would refuse the service of the man who keeps cranking after hearing cracking.

ps- in addition, that the mechanic will not admit that it was foolish or an "dumb moment" to continue wrenching after hearing cracking, adds to the doubt of his claims.

Originally Posted by Elvo (Post 13489865)

Isn't the OP the same guy that can't even tune his SRAM FD?

Originally Posted by I <3 Robots (Post 13489774)

I know Easton reinforces the clamping area on their carbon bars. IIRC, my Deda stem specs 8nm...but I always stop at 5.

That Cutter bar looks to be clear coated...possible its the clear that cracked and not the carbon?

Originally Posted by Elvo (Post 13489865)

Isn't the OP the same guy that can't even tune his SRAM FD?

Originally Posted by Elvo (Post 13489865)

Isn't the OP the same guy that can't even tune his SRAM FD?

Originally Posted by danvuquoc (Post 13489893)

LOL, I was thinking the same thing. So many bicycle problems from one person.

Originally Posted by Elvo (Post 13489888)

Was it these?

http://www.realcyclist.com/cutter-carbon-road-handlebar

RealCyclist might take them back...they have excellent CS

Originally Posted by ilovecycling (Post 13489871)

You, sir, are as ******** as your ability to form a proper sentence. Nothing you said here makes any sense, and it certainly didn't help whatever argument you are trying to make.

Originally Posted by Elvo (Post 13489888)

Was it these?

http://www.realcyclist.com/cutter-carbon-road-handlebar

RealCyclist might take them back...they have excellent CS

Originally Posted by danvuquoc (Post 13489893)

LOL, I was thinking the same thing. So many bicycle problems from one person.

Originally Posted by ilovecycling (Post 13489914)

If you are ever on the east coast, you are welcome to give my Look 595 w/ 6700 FD a spin. I think you would be pleasantly surprised at how well tuned the entire bike is, front shifting and all. Some bike setups don't like Red FDs and some do. Check with any reputable bike shop (roadwarrior's doesn't count :)) that has a fair amount of experience with SRAM products and they will tell you it's going to be a crap shoot when you leave out the door with a SRAM FD. That's just how it is, even if you have had great experiences with SRAM front shifting. But let's keep this one on topic, k?

Originally Posted by lhorn (Post 13489969)

Just to play devil's advocate, as long as he was well below the torque spec, I think he was right to keep torqueing. At least he ended up with an answer and he's safe.

What happens if he's still far from his intended torque spec and he and his friends hear a distinct "crack?" What do you do? Ride it knowing that it might not be tight enough (unsafe) or that it might be cracked (unsafe)? Bar looks ok visually...does that mean it didn't crack? Maybe not. It's not as though he kept torquing beyond manufacturer's spec.

Originally Posted by lhorn (Post 13490079)

I thought about this bar but the weight/price seemed too good to be true. I think I'm gonna stick with my heavy FSA bar.

Originally Posted by lhorn (Post 13490079)

[...] the bottom line is this was an ultra lightweight bar at a dirt cheap price. To me that means a thin bar/thin carbon which should at least suggest the possibilty that it might be a bit fragile or with cheap price, that quality control might be an issue.

I thought about this bar but the weight/price seemed too good to be true. I think I'm gonna stick with my heavy FSA bar.

Originally Posted by lhorn (Post 13489969)

What happens if he's still far from his intended torque spec and he and his friends hear a distinct "crack?" What do you do? Ride it knowing that it might not be tight enough (unsafe) or that it might be cracked (unsafe)? Bar looks ok visually...does that mean it didn't crack? Maybe not. It's not as though he kept torquing beyond manufacturer's spec.

Originally Posted by Brian Ratliff (Post 13488091)

The torque spec on a 3mm bolt means next to nothing. Torque specs are pretty much worthless for bolts less than 1/4" due to high variance in thread friction. To illustrate, insert the bolts dry and 5Nm will might have the bars slipping. Put grease on the threads and at 5Nm you might have enough bolt tension to crush the bars. The important is bolt tension; in big bolts, tightening torque correlates well with bolt tension. In a little bolt, thread friction is a huge factor and the correlation between bolt tension and tightening torque is not good.

Originally Posted by Looigi (Post 13491035)

Granted, but how then do you intuit correct tension for these fasteners?

Originally Posted by lhorn (Post 13489969)

Just to play devil's advocate, as long as he was well below the torque spec, I think he was right to keep torqueing. At least he ended up with an answer and he's safe.

What happens if he's still far from his intended torque spec and he and his friends hear a distinct "crack?" What do you do? Ride it knowing that it might not be tight enough (unsafe) or that it might be cracked (unsafe)? Bar looks ok visually...does that mean it didn't crack? Maybe not. It's not as though he kept torquing beyond manufacturer's spec.

Originally Posted by Brian Ratliff (Post 13491173)

If you hear a crack, you take the joint apart and inspect the bars. If the bars are still okay (the crack might have simply been coming from a misaligned screw), you put it back together, paying really close attention to how you tighten the bolts. You tighten until you can jump on the bars and not have them move. Like I was saying previously, the torque spec is a max, and it pertains to stripping the threads on the stem and has nothing to do with the bars.

Originally Posted by david58 (Post 13491196)

If I hear a 'crack' from a composite material, why would I put it back together? Not arguing here, but I really would like to understand the rationale that would have me continue to use a part made of CF from which I had heard cracking? I am hard-headed, but some what educatable (even if I can't spel), and would appreciate the info.