Is a cracked aluminium frame trash?

cavangoh
cavangoh Posts: 2
edited November 2017 in MTB general
I recently cracked my 7 year old polygon aluminium Hardtail, it was a great bike, but does it mean that it can't be ridden anymore?

Comments

  • cooldad
    cooldad Posts: 32,599
    Aluminium can be welded by a pro.
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  • trivial_poursuivant
    trivial_poursuivant Posts: 1,136
    cooldad wrote:
    Aluminium can be welded by a pro.

    It is still very difficult and expensive. Get a quote and find out if it’s a cost effective fix. Probably not worth it with Alu.
  • rockmonkeysc
    rockmonkeysc Posts: 14,774
    cooldad wrote:
    Aluminium can be welded by a pro.

    It can but the heat affected zone is very brittle leaving the frame quite a bit weaker than before and it obviously wasn't strong enough before if it broke.
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  • fudgey
    fudgey Posts: 854
    No one has asked yet where the crack is...

    Any pics?

    You guys obviously dont know any decent welders....
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  • trivial_poursuivant
    trivial_poursuivant Posts: 1,136
    Fudgey wrote:
    No one has asked yet where the crack is...

    Any pics?

    You guys obviously dont know any decent welders....

    Best welder in the world can’t repair damaged aluminium that easily. It’s not like welding steel. Heat effects it’s properties and leave it brittlecas mentioned. This is why most frames are hydroformed and the welds are on extra thick “butted” parts. A crack on a thin sidewall is pretty much terminal. This is where carbon can be easier to repair than metal.
  • rockmonkeysc
    rockmonkeysc Posts: 14,774
    I used to be a welder. Doesn't matter where it is on the frame, it will be weaker after welding.
    Aluminium frames are heat treated after manufacturing to relieve stresses and also temper the aluminium. Welding it after that heat treatment reintroduces stress due to heat distortion and also makes the parent metal around the weld more brittle.
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  • 02gf74
    02gf74 Posts: 1,171
    some Al alloys used for bike frames need sophisticated heat treating whereas other don't - many Al frames have been welded up successfully, sometimes with additional bracing.

    so you need to decide how much the frame is worth and how much it would cost to weld whether to go ahead, and depending on where it has failed, whether additional bracing is required.
  • trivial_poursuivant
    trivial_poursuivant Posts: 1,136
    Unless the frame is a particularly rare version or has sentimental value, I doubt any Alu frame is worth the cost of a repair. And even then there is no guarantee it will not break again in the future. And if that happens when you’re halfway down a hill you’ll certainly know about it.

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