is it really true that carbon frames, forks have just a certain number of yrs in them? 7-8 yrs tops? any truth on this? thanks
dennis
I’m not one to believe the hpye on the shelf life of a bike frame, as the evidence out on the road proves the opposite. I remember early aluminum frames would only last a few seasons, anyone out there on an old one? My old 1980 steel bianchi limited should be a wet noodle by now, it’s just like when I bought it, only as fast as I pedal it.
I would say some materials are prone to certain deteriorization. Steel rusts and carbon can delaminate, but for carbon, it won’t fall apart at a given time. I would think with fibre and resins they may never decay.
Aluminum has very poor fatigue resistance which is why your steel frame should last longer than higher priced aluminum frames.
Is the fatigue rate of Aluminum a result of age, frequency of use or both, (ie. would an older aluminum bike that was used mostly for racing be less fatigued than a bike of the same year that was used every day)?
but i heard from gerard, its more about how a frameset is designed w/ regard to failure/ cracking…the p2k was tested together with other brands one that cracked was a Ti framset
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Aluinum in general does, but that can be said of most metals. When they are mixed with some other materials, manipulated and set into a frame set. A blanket “Aluminum has very poor fatigue resistance” may still hold true, but not on a bike frame. It also tears easy, but frames don’t tear-apart after a while. You can bend things until they brake, but if you only bend them a little, they are not hitting a fatigue threhsold. I just think the wear out rate is highly exagerated as the small flexing isn’t like trying to snap a top off a soda can.
**Is the fatigue rate of Aluminum a result of age, frequency of use or both, (ie. would an older aluminum bike that was used mostly for racing be less fatigued than a bike of the same year that was used every day)? **
Caveat: This entire post stands at the mercy of our resident structural engineers and metallurgists.
I think the fatigue rate of aluminum is a matter of frequency of use. As I recall, aluminum doesn’t have a fatigue threshold (not proper term, I think)- every stress you apply to aluminum fatigues it. (As opposed to steel, in which only a stress above a certain threshold leads to fatigue.)
An aluminum bike is not going to get fatigued just sitting in your back bedroom. (If it has any epoxied joints, that’s another matter, I guess.)
That said, my bike is working just fine, and I seriously doubt that most people ever wear out a frame of any material.
I was reading a frame company’s website this morning and it stated they warranty their carbon frames for five years of racing and training. I take this as saying after five of use a carbon frame needs to be replaced. Every company is different as there are different grades and manufacturers of carbon.
**Is the fatigue rate of Aluminum a result of age, frequency of use or both, (ie. would an older aluminum bike that was used mostly for racing be less fatigued than a bike of the same year that was used every day)? **
Caveat: This entire post stands at the mercy of our resident structural engineers and metallurgists.
I think the fatigue rate of aluminum is a matter of frequency of use. As I recall, aluminum doesn’t have a fatigue threshold (not proper term, I think)- every stress you apply to aluminum fatigues it. (As opposed to steel, in which only a stress above a certain threshold leads to fatigue.)
An aluminum bike is not going to get fatigued just sitting in your back bedroom. (If it has any epoxied joints, that’s another matter, I guess.)
That said, my bike is working just fine, and I seriously doubt that most people ever wear out a frame of any material.
It’s called the endurance limit. You’ve got the basic idea right though; aluminum doesn’t have one and steel does.
An aluminum bike is not going to get fatigued just sitting in your back bedroom. (If it has any epoxied joints, that’s another matter, I guess.)
That said, my bike is working just fine, and I seriously doubt that most people ever wear out a frame of any material.
well said 
, as long as we dont crash it..but im a bit concerned with my chord fork…how many miles before you need to change it?
My old 1980 steel bianchi limited should be a wet noodle by now, it’s just like when I bought it, only as fast as I pedal it.
Huh? Why should it be “a wet noodle”?? It’s not as if the stiffness of the steel can change; nor can it for any other metal. As for fatigue resistance, in any frame it’s almost entirely governed by the quality of manufacture, no the material. A well made aluminium frame will far outlast a poorly built steel or titanium frame. If you are really worried about fatigue resistance of aluminium, never, ever fly on a commercial jet plane, since they are still primarily aluminium!
I agree that the blanket “Aluminium has very poor fatigue life…” is too broad and borderline plain untrue. Airplanes are made of the stuff and are subjected to much higher stresses of every kind (Temp change, flexing, UV exposure, catalyst fatigue, etc.) and last for many decades.
Carbon does fatigue, but I think that the new high quality frames are made from stuff you can expect to out last any rider you put on top of them.
Even though every material can be fatigued to the point of failure, I don’t thing that the stresses a bike frame is normally under is enough bring this about. Most likely cause of a bike frame failure is abuse or poor initial workmanship.
Of coarse I could totally wrong about this. I am an Enviromenal Biologist that sells Industrial machinery, not a Metalurgist.
Cervelo has a lifetime warranty on all of their frames, carbon or otherwise.
That’s why I wrote that, but people say your frame is shot if it’s 2 years old. I disagree and mentioned that if it kept on fatiguing it would be a wet noodle. As it is, I’m sure it’s as stiff as the day I bought it.
Cervelo warranties ‘defects in workmanship and materials’ and ‘Cervélo does not warrant against damage caused by normal wear and tear’ as per their site. This is a ‘Limited’ Lifetime warranty. Very, very different then a Lifetime warranty.
No no no. For a fatigue failure, first a small crack would open up in your frame, probably at a weld or braze. This would have no detectable effect on the ride or frame stiffness. As the loads were cycled, this crack would grow slowly until, someday, there would be insufficient strength in the remaining material that the crack would suddenly grow very fast and the frame would fail catastrophically. Even in the latter stages of slow crack growth, it could well not be detectable in terms of stiffness. If it was detectable, you would have to be very foolish to keep on riding it, because it could fail at any time. The phrase “wet noodle” doesn’t really cover any of this.
The failure mode of composites (e.g. carbon fibers matrixed in epoxy) is sudden catastrphic failure. Aluminum has a far kinder failure mode, in that the growth of the crack is eventually detectable. I’ve never seen an aluminum frame fail suddenly. Steel does the same thing as aluminum, but it takes more cycles. The analogy usually given is bending a paper clip until failure. An aluminum paper clip will tolerate fewer cycles than steel, but they both will ultimately fail, and in roughly the same mode. Composites just snap at their yield strength limit.
Having said you would be very foolish to continue riding a frame with an obvious fatigue crack, that’s exactly was doing early this year. Here’s a pic of the bb area of my old town hack, before it was retired for safety reasons. The crack actually went all the way around the back of the seat tube and then off up the downtube on the other side, in a symmetrical fashion.
I’ve never seen an aluminum frame fail suddenly.
It has happened. The early Cannondales were notorious for doing this at the headtubes. I’ve even had a steel frame fail on me suddenly, at a braze on the drive side chain stay.
I am certainly no expert in this category but I would venture a guess that most companies set their warranty based on how long they want to be responsible for dealing with a warranty replacement not how long they expect something to last.
I do agree that are fatigue limits and natural life spans for most anything out there but I still forked out for a Ti frame over an aluminum or carbon even though I would probably never wear out any material.