MCFK Stem hairlines Cracks
Moderator: robbosmans
Hello
After my ride yesterday, as cleaning my bike and notice this crack on my Stem, Upper Clamp of the Handlebar.
The cracks aren't seen in normal light, and you can fill them passing the fingernail.
Anyone add this problem.???
Before anyone start saying that is overtorque, it isn't and it wasn't, this stem was torque to Spec, with carbon paste, Effecto Mariposa 1-8Nm so fine tunning, and torqued to 3Nm acording to the manual of the Stem.
let me know on this.
After my ride yesterday, as cleaning my bike and notice this crack on my Stem, Upper Clamp of the Handlebar.
The cracks aren't seen in normal light, and you can fill them passing the fingernail.
Anyone add this problem.???
Before anyone start saying that is overtorque, it isn't and it wasn't, this stem was torque to Spec, with carbon paste, Effecto Mariposa 1-8Nm so fine tunning, and torqued to 3Nm acording to the manual of the Stem.
let me know on this.
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The lines you see are the different layers of carbon fiber that have separated/become delaminated.
I have two MCFK stems, one looks similar to yours and one doesn't. The one with the delamination I got brand new and came like that from the factory.
I wouldn't worry about it.
I have two MCFK stems, one looks similar to yours and one doesn't. The one with the delamination I got brand new and came like that from the factory.
I wouldn't worry about it.
Hello Thanks fot your answer.Lucendi wrote: ↑Mon Dec 13, 2021 5:26 pmThe lines you see are the different layers of carbon fiber that have separated/become delaminated.
I have two MCFK stems, one looks similar to yours and one doesn't. The one with the delamination I got brand new and came like that from the factory.
I wouldn't worry about it.
I've 3 of them and this is the only one that is like this, but just the top part, the bottom isn't, i've asked MARTIN from MCFK, waiting for an answer from them.
elfuinha wrote: ↑Mon Dec 13, 2021 5:18 pmHello
After my ride yesterday, as cleaning my bike and notice this crack on my Stem, Upper Clamp of the Handlebar.
The cracks aren't seen in normal light, and you can feel them passing the fingernail.
Anyone add this problem.???
Before anyone start saying that is overtorque, it isn't and it wasn't, this stem was torque to Spec, with carbon paste, Effecto Mariposa 1-8Nm so fine tunning, and torqued to 3Nm acording to the manual of the Stem.
let me know on this.
With what Lucendi has said (receiving a new one, like that) then from your pictures they're most likely planar voids from manufacture.
Assuming the MCFK stems are made from prepreg carbon, then it's not hugely surprising - when laminating many layers of prepreg, it's difficult to be sure that no air is trapped between the layers. Any air that is trapped is really difficult to remove with so many layers - even when using vacuum + autoclave.
I don't think there's any chance at all that your stem will fail from these, but lets see what MCFK say.
Reliable void-free manufacture is one reason THM moved to resin transfer moulding for at least some parts.
Assuming the MCFK stems are made from prepreg carbon, then it's not hugely surprising - when laminating many layers of prepreg, it's difficult to be sure that no air is trapped between the layers. Any air that is trapped is really difficult to remove with so many layers - even when using vacuum + autoclave.
I don't think there's any chance at all that your stem will fail from these, but lets see what MCFK say.
Reliable void-free manufacture is one reason THM moved to resin transfer moulding for at least some parts.
i don't think they are voids from manufacture, they really look like crackstjvirden wrote: ↑Mon Dec 13, 2021 6:43 pmWith what Lucendi has said (receiving a new one, like that) then from your pictures they're most likely planar voids from manufacture.
Assuming the MCFK stems are made from prepreg carbon, then it's not hugely surprising - when laminating many layers of prepreg, it's difficult to be sure that no air is trapped between the layers. Any air that is trapped is really difficult to remove with so many layers - even when using vacuum + autoclave.
I don't think there's any chance at all that your stem will fail from these, but lets see what MCFK say.
Reliable void-free manufacture is one reason THM moved to resin transfer moulding for at least some parts.
They may be; one way of getting an idea is if you vary the torque on the bolts - starting from 0 and bringing them to 3Nm, do the fissures (neutral term) change at all? Wider/narrower etc?
The thing about the alloy supports that directly take bolt load is that they (should) prevent any bending load on the carbon at that point. If there's no bending load, only compressive, it's difficult to see how cracks could form - for cracks like that to form there needs to be a shear force.
But again, Lucendi states seeing something similar on a new stem.
The thing about the alloy supports that directly take bolt load is that they (should) prevent any bending load on the carbon at that point. If there's no bending load, only compressive, it's difficult to see how cracks could form - for cracks like that to form there needs to be a shear force.
But again, Lucendi states seeing something similar on a new stem.
- pritchet74
- Posts: 1076
- Joined: Tue May 30, 2006 10:38 pm
- Location: NorCal
Well I wouldn't buy another MCFK stem. Personally, I am a huge fan of Extralite stems.
Have you ever wondered if there was more to life, other than being really, really, ridiculously good looking?
If you really believe that the stem is damaged you should cut it in half or destroy it some other way.
I personally can't see anything wrong with it..
Or you could ship it to Italy where I will gladly collect it.
Can you send pictures of your stem. ThanksLucendi wrote: ↑Mon Dec 13, 2021 5:26 pmThe lines you see are the different layers of carbon fiber that have separated/become delaminated.
I have two MCFK stems, one looks similar to yours and one doesn't. The one with the delamination I got brand new and came like that from the factory.
I wouldn't worry about it.
- Juanmoretime
- Administrator
- Posts: 289
- Joined: Sat Jun 19, 2004 11:08 am
I also have two MFCK stems in 100mm. One weighs 71 grams and the other 73 grams. I've had both for years and no cracks or issues. Did lubricate the bolts with anti seize and cabon paste on the carbon to carbon paste. 3mn of torque on the stem and handle bar bolts and no slippage. Love the stems!
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