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Supposedly this is one of the downsides of an aluminum frame, but I wonder how noticable it is. I'm a recreational rider and actually like my aluminum frame (maybe a little stiff but I like the fact that alot of pedal power goes to actually moving - plus I have a cushy seat :) ). Anywhoo... should I be concerned that my frame is falling apart, or is it a marketing ploy from those who build expensive frames?:rolleyes:

Thanks,
linuxted
 

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Metal is always tougher than man.

A certain % of any frame material will fail for a variety of reasons. A normal weight Alu frame is as safe as anything else out there.
 

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Once, I was bored and flexed an aluminum can back and forth until it came apart. Does that count?
 

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The most I ever put on an aluminum bike was a couple of thousand miles of road riding with a few skid-out in turn crashes here and there. I never saw a fatigue failure in any bike personally. I am also curious to hear from anyone who has actually seen, not an anecdote, mind you, but actually seen what they realized was a fatigue failure of an aluminum frame.
 

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I like to bend silverware and aluminum bike frames with my super psychic powers like Uri Geller.
 

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For many years now, I've heard the term "aluminum fatigue" used in stories about someone's aluminum frame suddenly breaking apart at 15 mph on buttery-smooth pavement. This particular bunch of cycling BS is probably based on a misunderstanding of how aluminum and steel tolerate repeated stress. In simple terms:

You can apply a specific load to steel indefinitely without failure as long as that load is under a certain limit. That limit is called the fatigue limit. Aluminum doesn't have a fatigue limit. Even a tiny load repeated often enough will make aluminum fail eventually. Frame builders know this, of course, so they design an aluminum frame to tolerate many more stress cycles than you can dish out in decades of normal use. Forget about "aluminum fatigue" and enjoy your bike.
 

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Fat Guy in a Little Coat
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rocco said:
I like to bend silverware and aluminum bike frames with my super psychic powers like Uri Geller.
After seeing Rocco's silverware pictures, I'm afraid eating will fatigue my flatware! :D

Seriously, the only frame failure I'm personally aware of is a friend's Raleigh Technium frame, which broke on one of the chainstays behind the bottom bracket while on a trainer. I have heard that these were not the most reliable frames, and don't know whether it was due to fatigue, poor materials, poor design, or a combination.

I don't think you have anything to worry about...
 

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wim said:
For many years now, I've heard the term "aluminum fatigue" used in stories about someone's aluminum frame suddenly breaking apart at 15 mph on buttery-smooth pavement. This particular bunch of cycling BS is probably based on a misunderstanding of how aluminum and steel tolerate repeated stress. In simple terms:

You can apply a specific load to steel indefinitely without failure as long as that load is under a certain limit. That limit is called the fatigue limit. Aluminum doesn't have a fatigue limit. Even a tiny load repeated often enough will make aluminum fail eventually. Frame builders know this, of course, so they design an aluminum frame to tolerate many more stress cycles than you can dish out in decades of normal use. Forget about "aluminum fatigue" and enjoy your bike.
To add to wim's comment, similar BS-es also get circulated about carbon frames shattering into small deadly pieces upon contact with non-Kentucky blue grass on the side of the road. Unless a frame is very poorly welded or glued, or that it has been in a serious accident, I wouldn't worry about such stories.

The internet is also wonderful for being a great medium for passing along pictures and video and text describing something, but not all get to the same people at the same time. There are tons of photos of trashed frames without the accompanying explanation to them. However, they make great ammo for propagating "truthiness" and exaggerated tales of failures.
 

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Discussion Starter #10
rocco said:
I like to bend silverware and aluminum bike frames with my super psychic powers like Uri Geller.
Holy mashed potatoes Batman! What happened to that Cinelli?!
 

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aluminum framebuilders use oversize tubes to make frame stiffer
as well as use thick tubing to produce durable, stifff, and light (aluminum less dense than steel) frame.
 

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Exactly....

The reason that most aluminum frames are so stiff is that the manufacturers have made the frames such that they perform really well, and have a margin of safety. So most riders will not face the heartbreak of aluminosoriosis. Nevertheless, the aluminum fatigue phenomena is real, just one that most riders won't have to worry about.

I have seen trashed mountain bikes--some were acute incidents (big hits) but some were chronic (that is, fatigue-related) failures. Some at the downtube/headtube junction, a few were at the chainstays.

Also, I saw two old aluminum road frames that had come apart under unknown circumstances--they were in a frame scrap pile--but it seemed that they were failures and not crashes. Both were old school small-tubed aluminum. I think both were French. And, finally, I was recently reading about some frame abuse testing and the aluminum Klein frame failed at a cable entrance.

Also, haven't we all seem handlebar and stem failures over the years? I personally broke my share of back-in-the-day stems and bars, many French. AVA were my favorite breakers. Almost drove a stem through my sternum once on a downhill run. Now, I don't use stems or bars that are heavily used after about five years. I saw a guy go endo on his commuter because his ttt quill stem let go.

Aluminum does the job, just don't ask it to do the job for ever and ever.


steel515 said:
aluminum framebuilders use oversize tubes to make frame stiffer
as well as use thick tubing to produce durable, stifff, and light (aluminum less dense than steel) frame.
 

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"I have seen trashed mountain bikes--some were acute incidents (big hits) but some were chronic (that is, fatigue-related) failures. Some at the downtube/headtube junction, a few were at the chainstays. "

Could you give more details of the fatigue related failures? Welded frames? The chainstays were at the BB? I'm wondering how you drew the conclusion that they were fatigue related. Were crashes involved? What happened at the junctions?

BTW I have had the aluminum handlebar of my 85 Cannondale break in 93 when I jumped a curb. Was it fatigue related? I have no clue. I did not analyze it.
 

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does this count as fatigue

I've seen several Al frame failures amongst my friends. I have seen a few CF failures and steel as well but at a much lower rate. No Ti failures that didn't involve a crash. I personally broke 2 Al frames and I am no heavyweight; I'm a 150 lbs strong rec. rider. The first one was about 6 months after the frame was purchased and occured at the rear dropout, was replaced under warranty. That was undoubtedly a manufacturing defect, probably overheating during welding. The replacement frame cracked at the downtube after 4 years and was denied warranty. Neither frame was involved in any extraordinary trauma and the frames were above average weight for AL. I quite liked the frames' ride qualities in all respects, but I will certainly not buy another, and I went back to steel. Welded. Look at the photo and tell me if this counts as fatigue?
 

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linuxted said:
Holy mashed potatoes Batman! What happened to that Cinelli?!
What happened was a moron in a SUV who suddenly swerved and stopped short in the bike lane right in front of me. I guess getting on the Dan Ryan expressway was really important to her. :rolleyes: I spent the night at Cook County Hospital with a nasty concussion. That's a bad memory and non-memory if you know what I mean.
 

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Post-yield vs. non-yield fatigue

alienator said:
Once, I was bored and flexed an aluminum can back and forth until it came apart. Does that count?
Not really. That's an example of post-yield fatigue, which is quite a bit different from the non-yield fatigue most often experience by bicycle frames.

In post-yield fatigue, the component is flexed past its yield point, is permanenty deformed with each load cycle. In non-yield fatigue, the load cycles can be below the component yield point, and damage can occur without permanent deformation.
 

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rocco said:
What happened was a moron in a SUV who suddenly swerved and stopped short in the bike lane right in front of me. I guess getting on the Dan Ryan expressway was really important to her. :rolleyes: I spent the night at Cook County Hospital with a nasty concussion. That's a bad memory and non-memory if you know what I mean.
I hope you gave that idiot in the SUV a piece of your mind.
" You talk the talk, do you walk the walk?"
 

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flattire said:
Yes that is a Pinarello.
Bummer. That's an expensive way to fill a dumpster. :(
 
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