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Old 02-12-06, 10:03 AM   #1
paul8f
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Crack in Aluminium Frame

Hi,

I have a 1997 Giant alumium mountain bike (or as the US spell it 'aluminum'). I have a crack in the frame on the drive-side chainstay. It's at the bottom bracket end near the weld on that little support strut that braces the two chainstay arms together.

It's on the inside of the tube and slowly getting bigger. I am no longer racing this bike and now I just want to use it as a commuting bike. I've been told that if I got aluminium welded, it should be heat treated afterwards so that it won't fail.

This would be way too expensive so can anybody offer me any advice on how to repair the frame?

Thanks,
Paul
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Old 02-12-06, 10:48 AM   #2
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Does Giant have a lifetime warranty on the frame? Maybe you can get it replaced.
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Old 02-12-06, 02:03 PM   #3
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I've also heard that aluminium repair isn't so easy. I don't know where you are, but these guys recently posted an ad on San Francisco Craigslist claiming they can do aluminum bike repairs: http://www.craigslist.org/pen/bik/133060204.html (http://mrrpmwelding.net).
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Old 02-12-06, 10:01 PM   #4
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Quote:
Originally Posted by paul8f
Hi,

I have a 1997 Giant alumium mountain bike (or as the US spell it 'aluminum'). I have a crack in the frame on the drive-side chainstay. It's at the bottom bracket end near the weld on that little support strut that braces the two chainstay arms together.

It's on the inside of the tube and slowly getting bigger. I am no longer racing this bike and now I just want to use it as a commuting bike. I've been told that if I got aluminium welded, it should be heat treated afterwards so that it won't fail.

This would be way too expensive so can anybody offer me any advice on how to repair the frame?

Thanks,
Paul
Break the crack line & fill with Alumalloy
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Old 02-12-06, 11:27 PM   #5
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Aluminum (US)
Aluminium (EU)
Alumium (???)
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Old 02-13-06, 12:58 AM   #6
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Originally Posted by sngltrackdufus
Break the crack line & fill with Alumalloy

What is this stuff? A glue or something? And where is it sold?
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Old 02-13-06, 07:19 AM   #7
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Aluminum (US)
Aluminium (EU)

Alumium : Typing too fast!!

*How expensive is this Alumalloy stuff? Does it last?
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Old 02-13-06, 03:58 PM   #8
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Do yourself a favor inspect the frame carefully for additional cracking, if you don't see any take it to a Professional Welder with TIG capability. There is a lot of stress on the chainstays, definately don't mess with an epoxy, the results could prove painful. Then ride it till it cracks again (which will likely be somewhere other than the new weld if at all) at which time I'd scrap it.
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Old 02-14-06, 04:52 PM   #9
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Yeah, I'm thinking that the epoxy solution would only be a temporary fix as well. However I'm only 60 Kg (132 pounds) and the bike will only be used to get around, so it could actually work out.

I've heard a story where a college welding instructor refused to repair a students motorcycle frame because he said he could be held liable when the frame fails. (he knew the student wasn't going to pay for the frame to be heat soaked etc..). The stresses on a motorbike frame would be a lot greater than that of a mountain bike frame so I think I might chance going in search of someone with TIG welding experience.

Then again, there's always stickytape.....!!
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Old 02-15-06, 12:14 AM   #10
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You could pick up a non broken one on ebay for 50 bucks. To repair that frame would probably be more expensive and more time consuming.

Which is of course why god invented steel
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Old 02-19-06, 01:35 AM   #11
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Don't think you can save the frame. You would have to have heat treat the whole frame back to annealed state then reweld the crack then do a second heat treat to bring the strength back up. If you weld the crack in its present state, you may end up a crack in the new weld.
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Old 02-21-06, 12:46 PM   #12
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Originally Posted by Thylacine
You could pick up a non broken one on ebay for 50 bucks. To repair that frame would probably be more expensive and more time consuming.

Which is of course why god invented steel
Amen brother!!

There's a reason the major framebuilders went to limited 7yr warranties on aluminum frames.
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Old 02-28-06, 06:51 AM   #13
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Quote:
Originally Posted by dlbcx
Don't think you can save the frame. You would have to have heat treat the whole frame back to annealed state then reweld the crack then do a second heat treat to bring the strength back up. If you weld the crack in its present state, you may end up a crack in the new weld.
A genius
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