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scratch in carbon bars?!?!

LoUiS1985LoUiS1985 Posts: 841
edited July 2009 in MTB workshop & tech
Hi All,

I have just fitted some FSA K-force carbon bars to my hardtail. Unfortunately i fitted the left hand side shifter clamp on the opposite way round and didn't notice until i had fitted my lock on grip.

Whilst taking the grip back off i had to twist the grip whilst easing it off, which led to the metal lock on ring rubbing on the bar and causing a scratch round the circumference of the bar, about 1mm(ish) indentation. What do you guys reckon as i obviously dont want the bars integrity compromised or the bars snapping in mid flight??

Sorry i cant upload any pics as i'm on work computer and my home computer is out of action for a while

Cheers guys :?

Posts

  • nicklousenicklouse Posts: 81,520 Lives Here
    pics but if 1mm i would say it is scrap.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Dunk_911Dunk_911 Posts: 239
    I have a carbon frame which got a chip last year and i learnt this;

    weakness in carbon ccan come from an irregularity in the surface of the material (your scratch) and allowing water/ elements into the weave through any exposed area of carbonwill cause de-lamination (thats separation of the carbon layers).

    obviously your bars are quite lightweight so probably do not have a particularly thick wall, but depending on the thickness of the wall compared to the depth of the scratch you could get away with it if you were to very gently sand down the area around the scratch to 'remove' the scratch (though obviously attempting to remove as little material as possible). then i would get some nail varnish of clear enamel (basically a solvent based laquer or paint) and paint it onto the area surrounding the exposed surface.

    it is still a weak point however and you should remember this but my frame is still going 8 months on although the chip was quite shallow.

    if it was me though i would just get some bars, i run these because they are cheap, lighter than most carbon bars and alloy so they are less likely to snap un-expectedly!

    http://www.chainreactioncycles.com/Mode ... elID=19579


    Good luck!
  • antflyantfly Posts: 3,448
    If it`s that delicate that you can`t use it when scratched then I don`t know how anyone can use carbon on a MTB.
    Smarter than the average bear.
  • LoUiS1985LoUiS1985 Posts: 841
    after re-checking the bars i'm sure they are fine and i have used them several times now for XC use with no probs.
  • Tank-slapperTank-slapper Posts: 968
    If the scratch hasn't gone into the weave, just follow the advise above about gently sanding out the scratch and re-varnishing it. Do it as soon as possible and there shouldn't be a problem.
  • LoUiS1985LoUiS1985 Posts: 841
    If the scratch hasn't gone into the weave, just follow the advise above about gently sanding out the scratch and re-varnishing it. Do it as soon as possible and there shouldn't be a problem.

    yes that's what i did do and am 99% sure they are just as reliable as before i scratched them
  • Dirtydog11Dirtydog11 Posts: 1,621
    antfly wrote:
    If it`s that delicate that you can`t use it when scratched then I don`t know how anyone can use carbon on a MTB.

    Same applies to alloy that's why most alloy bars are shot peened!
  • antflyantfly Posts: 3,448
    But if I scratch my alloy bars I don`t worry about them snapping or consider replacing them or sanding them down.
    Smarter than the average bear.
  • Dirtydog11Dirtydog11 Posts: 1,621
    But if I scratch my alloy bars I don`t worry about them snapping or consider replacing them or sanding them down.

    What, even if you put a scratch around the circumference.
    Mmmm.....are you sure? Only that's not what I've been lead to believe. If I'm not mistaken Easton recommend changing your bars every three years. Scratched or not!

    I will stick to manufacturers recommendations. After all you wouldn't consider tightening a carbon bar up without a torque wrench would you? So why would I choose to ignore their reccommendations when it comes to replacement /damage?
  • Chaz.HardingChaz.Harding Posts: 3,228
    I run DH alloy bars. They are THICK!

    Doubt they'll snap anytime soon. Probably bend, but I'd hate to think that the force required to bend them would travel through my arms :shock:

    I'd have no bloody arms left!!! :lol:

    And about not tightening carbon bars without a torque wrench.... Yup, I'm quilty. NOTHING on ANY of my bikes gets the torque-wrench treatment. I am, however, careful when tightening. And for the record, I build, service and maintain all of my bikes, from repairing puntures to fork servicing!
    Boo-yah mofo
    Sick to the power of rad
    Fix it 'till it's broke
  • skylinerskyliner Posts: 613
    It's not water you need to worry aout in terms of delamination. Some carbon composites are tested at 70 degrees under water, and others at higher temps in oil.
    Solvents though, can break down the resins used in some composites. So I wouldn't use solvent based products on a carbon fibre component with scratches in the laquer.
    It'll take time to compromise the strength in the weave, and will appear to be fine for a while, but I wouldn't take chances with it.
    It's nice to be important, but it's more important to be nice.
  • smorgsmorg Posts: 12
    you could polish the scratch up so it appears less visable or do that and rub some laquer in to it but if it has not touched the carbon i would rubs the whole bars down evenly and relaquer them
  • Daz555Daz555 Posts: 4,040
    Dirtydog11 wrote:
    If I'm not mistaken Easton recommend changing your bars every three years. Scratched or not!
    3 years! I'd still regard them as brand new after 3 years.
    You only need two tools: WD40 and Duck Tape.
    If it doesn't move and should, use the WD40.
    If it shouldn't move and does, use the tape.
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