Does current aluminum fatigue?

[giverdada]

I heard it a lot, as I suffered through poundings issued by my thirdhand Cannondale R800 from the 80s: aluminum fatigues.

I rode that Cdale forever, mostly commuting after my dreams as a competitive rider evaporated like WD40 in the sun, and I got more beat up by it every year. Streetcar tracks here in Toronto became a special torture. It was never a crazy stomp-and-go frame once the new-road-bike feeling wore off, but it got worse per ride. Finally, I had to let it go and get some newer aluminum.

My 1997 Specialized S-Works mountain bike was the nicest aluminum I have ever ridden. Really light, really responsive, and it didn't rattle me off the bike, or the bike off the trail. Amazing frame, even after I cracked it doing freeride dives I shouldn't have. It felt like..titanium.

My brother is looking at bike options for his lady, and the topic of aluminum came up. My CX bike is aluminum and it's great. My next mountain bike will be aluminum. And I lust after Gaulzetti while keeping an eye open for a 52cm CAAD10 for my mom.

Does aluminum fatigue? I don't know anything about engineering or metallurgy, but am interested in the fatigue factor of aluminum bicycle frames. I think they become 'dead'. But I don't KNOW that they become dead. Anyone?

[hampco]

Aluminum is aluminum but this may help, despite its age:

http://www.ibiscycles.com/support/te...ght_and_shiny/

[Mark McM]

Are current aluminum alloys subject to fatigue? Yes.

Are current steel alloys subject to fatigue? Yes.

Are current titanium alloys subject to fatigue? Yes.

Will a properly designed and manufactured metal frame suffer from fatigue failure during its normal lifetime, if subjected to its intended usage? Usually not.*

Do metal frames (aluminum, steel or titanium) get "soft" when the fatigue? No.

[sparky33]

Originally Posted by giverdada

while keeping an eye open for a 52cm CAAD10 for my mom.

I don't know much about metals, but I'm pretty sure that your mom must be awesome.

[carpediemracing]

Originally Posted by sparky33

I don't know much about metals, but I'm pretty sure that your mom must be awesome.

+1, my first thought also.

If she'll consider a 52 cm SystemSix give me a holler.

I use aluminum frames. Some have cracked/failed (old Cannondale original pre-3.0 stuff, 2 Giant TCRs, 1 M2 S-Works, every single one right chainstay), my current ones are going strong.

[mtechnica]

Yes, aluminum fatigues. If you bend it enough times it will eventually break whereas steel, within a certain range, can flex nearly an infinite amount of times without breaking. As far as aluminum bicycle frames, it doesn't really seem like a concern to me as most of them aren't flexing enough and seeing enough cycles to break within any kind of timeframe that a user would worry about.I don't believe aluminum frames become dead or work harden to any noticeable degree. It would become brittle and break before it work hardened (imagine bending a paper clip)

[Mark McM]

Originally Posted by mtechnica

Yes, aluminum fatigues. If you bend it enough times it will eventually break whereas steel, within a certain range, can flex nearly an infinite amount of times without breaking.

What you are describing is call the Endurance Limit (maximum stress that a material can endure for an infinite number of loading cycles without breaking). Low alloy mild carbon steels tend to exhibit an endurance limit, but high alloy steels do not. Since bikes are built from high alloy steel, I'm not sure we can assume that they have an endurance limit.

Instead, engineers usually design around a fatigue limit. This is the maximum stress of repeatedly loading that a material can withstand for some fixed number of loading cycles (usually 1,000,000 cycles).

[wildboar]

Um...I have one of these I'd sell, in case you ever want to re-capture the magic!

Originally Posted by giverdada

I heard it a lot, as I suffered through poundings issued by my thirdhand Cannondale R800 from the 80s: aluminum fatigues.

I rode that Cdale forever, mostly commuting after my dreams as a competitive rider evaporated like WD40 in the sun, and I got more beat up by it every year. Streetcar tracks here in Toronto became a special torture. It was never a crazy stomp-and-go frame once the new-road-bike feeling wore off, but it got worse per ride. Finally, I had to let it go and get some newer aluminum.

[brando]

Originally Posted by giverdada

Does aluminum fatigue? I don't know anything about engineering or metallurgy, but am interested in the fatigue factor of aluminum bicycle frames. I think they become 'dead'. But I don't KNOW that they become dead. Anyone?

I've read about this stuff and the myth of the dead frame. Yet, I've had it happen to me twice. An early '90s aluminum Klein and an '80s steel SLX. Maybe some other factors can explain it, but those frames rode great for years then just felt slow and dead.

[LesMiner]

Originally Posted by brando

I've read about this stuff and the myth of the dead frame. Yet, I've had it happen to me twice. An early '90s aluminum Klein and an '80s steel SLX. Maybe some other factors can explain it, but those frames rode great for years then just felt slow and dead.

Is it possible that it is you aging and not the frame?

[Black Dog]

Originally Posted by brando

I've read about this stuff and the myth of the dead frame. Yet, I've had it happen to me twice. An early '90s aluminum Klein and an '80s steel SLX. Maybe some other factors can explain it, but those frames rode great for years then just felt slow and dead.

Not the frame. Rider perception...you got used to them and bored.

[11.4]

Practically speaking, I believe that most of the CAAD10 frame failures did happen in the right chain stay, but they also happened in the weld at the stay end. So the issue, as far as actual breakage is concerned, is less about the tubing and more about welding methodology. Cannondale and others have learned a lot from the history of alloy frames and their welds are now rated for far more cycles -- virtually infinite for purposes -- than back in the earlier days of the CAAD series. It was thought back then that the tubes would fatigue and fail first; instead it was the welds. Now they have lifetime guarantees against breakage and to my knowledge Cannondale is seeing negligible breakage rates on the more recent models, both on the road and in the lab.

As for softening, that isn't really what happens -- they don't get more flexy with age -- so if you're considering an alloy frame, go for it. For both breakage and long-term ride performance they do very nicely.

The only potential issue with alloy frames is when you get a substantial dent in them. Dents can cause local issues that may lead to breakage at a greater frequency than in steel. However, we're still far ahead of carbon fiber and not far behind steel, and denting up your frame isn't really part of your plan anyway.

[brando]

Originally Posted by LesMiner

Is it possible that it is you aging and not the frame?

Zing! Nope, I'm at my fastest in years right now. Race results and Strava times bear it out.

[unterhausen]

aluminum might not have an indurance limit, but as a practical matter a properly designed part can last many lifetimes. I have sat next to a fatigue macine waiting for a piece of aluminum to break without joy too many times.

[BobO]

Originally Posted by unterhausen

aluminum might not have an indurance limit, but as a practical matter a properly designed part can last many lifetimes. I have sat next to a fatigue macine waiting for a piece of aluminum to break without joy too many times.

Aluminum can develop fatigue cracks when it is given unrelieved stress risers. This is the reason airliners have radiuses on the penetrations in the airframe.