Carbon Bars Scored: Replace?

Forums Mountain Bike Forum Carbon Bars Scored: Replace?

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    • #240874

      They weren’t tight enough and they spun a bit during my ride yesterday. Took them off this morning to inspect. Should I be concerned?

       

    • #240877

      Yes, be concerned. That is a definite stress point now.

    • #240882

      I would replace them. No need to take chances with safety.

    • #240885

      That looks pretty significant.

      • #241166

        That’s not how carbon fiber works. Composites are not notch sensitive, as determined by an Izod or Charpy test. Aluminum parts are monolithic and crystalline and  and a small scratch can propegate into a crack and then a fracture.  A moderately deep scratch on a bar or steer tube that appears superficial can lead to complete fracture.

        Composites are completely different. That appears to be a surface scratch of the resin. With damage to carbon you want to look for evidence of delamination or broken fibers.  Impacts or bending can cause delamination and cuts and abrasion can break fibers.  If the scratch is deep enough to cut through the fibers you may have a problem, but because there is no crystalline medium for a crack to propegate through that scratch is not a stress riser, but an area where the tensile strength is reduced only to the degree to which fibers are broken. Good engineers build with a safety factor of at least 2, ie the part is twice as strong as necessary. If a single layer of fibers is damaged and there is no delamination, you are likely still within safe limits because the fibers damaged are a very small percentage of the materials contributing to the strength of the part.

        In addition, the damage is toward the end of the bar which is under much less stress than near the stem.  I work with composite body armor and as a road racer have a lot of experience riding damaged carbon fiber parts, because crashes are a part of life and your bike is always messed up to a degree. I’d say that the band clamp on a road lever can score the clear coat of a carbon handlebar as badly as that on installation.

    • #240904

      Thanks for the input guys, theyve been swapped for the stock aluminums. You guys are right, no need to risk safety. Bought those with store credit I got for buying the bike, part of the black friday special they were running. So not the worst loss. Ill have to be more careful in the future with carbon bars If I chose to try them again. They spun when i nose dived off a drop and went OTB. Think they were tight enough and it was just the excessive force of my weight that caused them to spin? Maybe they should’ve been tighter?

    • #240906

      IceToolz makes a cheap and reliable torque wrench for maybe 20 bucks at your LBS or eBay or wherever. Use it on all the bolts and nuts every ride or two, ESPECIALLY on carbon parts. Much cheaper than replacing carbon parts, or having your bike fall apart on the trail.

    • #240916

      Contact Race Face. They have warranty and crash damage discount programs.

       

       

       

      • #241061

        Thats awesome info and awesome customer service.

    • #240917
    • #241000

      Yeah, I really should get a torque wrench. Lesson learned the hard way. Ill have to check out the IceToolz. Ive seen the prest ones, I like the idea of having a few of those versus an adjustable though.

      Thanks for the info Mike, Im definitely gonna check that out.

    • #241169

      Thanks @Sean Gordon. I have a similar understanding, but with stuff like this I think most people aren’t willing to take the risk. If it were my bar, I would probably keep riding it, based on my knowledge of carbon fiber construction. However, the OP should make his own decision based on his level of comfort, and not the advice of anonymous internet engineers. 🙂

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