Cracks in carbon bar

[jzinckgra]

I was going to use these bars on a bike build, but just noticed what look like stress fractures on either side of stem mount. I assume the bar is junk and should not use it?20220117_093655.jpg20220117_093640.jpg

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[zap]

hmmm, the distance on either side of the stem looks identical.....like aero bars were installed.

[sevencyclist]

Would not trust your safety with these cracks. The savings from reusing this bar is not worth it!

[Elefantino]

Originally Posted by zap

hmmm, the distance on either side of the stem looks identical.....like aero bars were installed.

Yep. And over-torqued.

It's toast.

[jzinckgra]

Bummer but better safe then sorry. Thanks.

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[soulspinner]

Especially the second pic...not looking good.

[Mark McM]

Maybe its just coincidence, but there appears to be a seam/discontinuity across the clamp area that is co-linear wit the "cracks" on either side. I'm wondering if there isn't some inherent flaw in the construction?

[.RJ]

meatball mechanic

[m_sasso]

Many handlebars are not designed, reinforced to support clip on aero bars or intermediate brake levers, usually silk screened on the bar or specified in the original owners manual. Who made the bars and what model are they?

The previous owner may have ignored the bar specs or over tightened the previous set up, difficult to know at this point. The left side pinching appears to have resulted in more crack damage than the right, however they are done.

[dddd]

I agree with the clamp scenario, this looks identical to how some carbon seatposts look after being damaged at the clamp at the upper end of the seat tube.

Not sure how the operational strength will be affected since the seatposts I saw didn't fail, but the bars were likely never tested in anything like there current condition so can't really be trusted.

[FriarQuade]

They look done, but if they're high end bars and you really want to use them there are people that do NDT on carbon parts. Not sure if they take on the liability of bars or if it's economical though. I know Ruckus does inspection work, not sure if there's anyone on the east coast though. I wouldn't use them without a specialized inspection though.

[jzinckgra]

Originally Posted by dddd

I agree with the clamp scenario, this looks identical to how some carbon seatposts look after being damaged at the clamp at the upper end of the seat tube.



Not sure how the operational strength will be affected since the seatposts I saw didn't fail, but the bars were likely never tested in anything like there current condition so can't really be trusted.

I was most concerned about out of the saddle sprints. I don't sprint much but had visions of catastrophic failure. After crashing and breaking my elbow last summer I think I'll toss the bars

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[maj]

If you do decide to toss them, it would be interesting to set them up and stress them to point of failure. Just to see what they’ll take and how they eventually fail.

[BdaGhisallo]

Originally Posted by maj

If you do decide to toss them, it would be interesting to set them up and stress them to point of failure. Just to see what they’ll take and how they eventually fail.

That would be interesting. Hearing so many tales of damaged fork steerer tubes, I once took a cut off piece of an Enve 1.125" steerer tube and put it in my vice and tried to squash it. I was quite surprised by how much it took to really deform and damage that tube.

[Mark McM]

Originally Posted by BdaGhisallo

That would be interesting. Hearing so many tales of damaged fork steerer tubes, I once took a cut off piece of an Enve 1.125" steerer tube and put it in my vice and tried to squash it. I was quite surprised by how much it took to really deform and damage that tube.

Insert a wedge between the steerer and one of the vice faces to apply a concentrated point load on the steerer. You might find a different result. Carbon if very strong - when loads are well distributed across the fibers. But it is also brittle and doesn't like high point loading. The steerer failures we hear about typically occur where the edges of stems or compression rings cause high point loading. Metal is often more tolerant of high point loading, and will yield before fracturing.