How unsafe is a bent AL frame?

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2009-08-28 2:46 PM

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Expert
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1000100
Thornton, CO
Subject: How unsafe is a bent AL frame?
I'm not a material expert, but I know some basics about why my bike is being replaced by the insurance company.  It's an AL frame and the bike shop shop said you can't bend it back (I think it was off by 3/4" ?).  I know AL fatigues each time it's bent unlike steel. 

So my question is, if I leave the frame bent, put some cheap forks back on it is it still safe to use as a commuter/grocery-runner bike?  There's no cracks in the welds, no paint chips/cracks from where it might have bent, and no visual cracks anywhere to be found.  I'd feel much more comfortable locking up a bike I was assuming was useless than taking the new one I'll be getting, but not at a high risk of my own safety in the event of another accident.

2009-08-28 3:00 PM
in reply to: #2376989

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Cycling Guru
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Fulton, MD
Subject: RE: How unsafe is a bent AL frame?
I've been told by reps from various manufacturers not to re-use aluminum frames with any damage.

But I've owned one with a big old ding in one of the tubes (chain stay) and didn't care at all and raced it.

I would be cautious depending on where the dent is though.  Head or tob tube and I would not ride it anymore personally.
2009-08-28 3:26 PM
in reply to: #2376989

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Expert
1116
1000100
Thornton, CO
Subject: RE: How unsafe is a bent AL frame?
There are no visual dents that I can find.  It's just that from the entire length (head tube to seat post tube to derailleur hangers) when you compare one side to the other is different by 3/4".  So the frame was "tweaked" during the accident, but not in any one given location that I can find.
2009-08-28 3:32 PM
in reply to: #2376989

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Cycling Guru
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Fulton, MD
Subject: RE: How unsafe is a bent AL frame?
Your call.  But I'd be leery of riding that .....

Edited by Daremo 2009-08-28 3:32 PM
2009-08-28 3:42 PM
in reply to: #2376989

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Ventura County, California
Subject: RE: How unsafe is a bent AL frame?
With steel, I would put it on an alignment table and bend that sucker back to true and then ride it all day. With aluminum, I would toss it out. Steel can take a whack and bounce back... aluminum, not so much. Even if there are no external signs of damage, it is for-sure weaker now. That Aluminum frame is now way more likely to have a catastrophic failure someday.

Edited by TaylorB 2009-08-28 3:43 PM
2009-08-28 3:58 PM
in reply to: #2376989

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Expert
1116
1000100
Thornton, CO
Subject: RE: How unsafe is a bent AL frame?
ok.  Just wanted to make sure my original thought that it's junk wasn't wrong.  No need to risk my neck for it.  I'll probably become a permanent fixture on the wall or on the CycleOps.

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