Alu MTB Frame life limited?

[x]

Just saw a post on alt.mountain-bike ("Foes Customer Service - someone else doin' it right") that
contained the statement:

"Believe it or not, if ridden off-road for that long (minimum it seems 5 years) just about any
aluminum frame will break."

I've heard others say that this is nonsense, but source seems pretty reliable.

OTOH, airplane frames last a lot longer than 5 years...

Comments?
-----------------------
Pete Cresswell

 

[Thomas Reynolds]

"(Pete Cresswell)" <[email protected]> wrote in message news:<[email protected]>...
> Just saw a post on alt.mountain-bike ("Foes Customer Service - someone else doin' it right") that
> contained the statement:
>
> "Believe it or not, if ridden off-road for that long (minimum it seems 5 years) just about any
> aluminum frame will break."
>
> I've heard others say that this is nonsense, but source seems pretty reliable.
>
> OTOH, airplane frames last a lot longer than 5 years...
>
> Comments?
> -----------------------
> Pete Cresswell

My comments are limited. I don't claim to be an expert. I am a roadie who puts in 6K-10K miles per
year and all but one of my bikes are steel. The one that is not is a new aluminum bike that I am
still putting together.

From my materials class in college I learned that aluminum is not a good spring. Consider a road
fork as an example. As you travel down the road every small bump causes a small deflection. A steel
fork is very good about going back to its original position. An aluminum will never quite to that.
It should be possible to wear out an aluminum bike, not break them.

Others who ride aluminum bikes have commented to me how after a few years the stiffness that was
present when the bike was new seems to go away. Obviously this is subjective but I expect my new
aluminum frame to need replacement in a few years.

Tom

 

[Paul]

I have no meaningful knowledge in the field of materials science although I have come across talk of
the fatigue life of aluminium with regards bicycle frames before.

The only thing I have to add to this thread is the simple fact that the manufacturers of the bike I
ride (Dawes in the UK) provide a 15 year warranty on their steel frames but only 3 years on their
aluminium ones which does sort of suggest that there is an expectation that alu. frames will fail
long before steel ones. That said some bicycle manufacturers do seem to offer much longer warranty
periods on alu. frames. I know nothing about the differant types of aluminium alloy - do they have
different fatigue characteristics? My cycle is plain guage aluminium and defined as 7005 HT.

Kind Regards, Paul

 

[John Everett]

On Fri, 17 Jan 2003 15:12:27 GMT, "(Pete Cresswell)" <[email protected]> wrote:

>Just saw a post on alt.mountain-bike ("Foes Customer Service - someone else doin' it right") that
>contained the statement:
>
>"Believe it or not, if ridden off-road for that long (minimum it seems 5 years) just about any
>aluminum frame will break."
>
>I've heard others say that this is nonsense, but source seems pretty reliable.
>
>OTOH, airplane frames last a lot longer than 5 years...
>
>Comments?

Anecdotal evidence; my son's aluminum Gary Fisher (pre-Trek) is at least ten years old. Still
going strong.

jeverett3<AT>earthlink<DOT>net http://home.earthlink.net/~jeverett3

 

[Ajames54]

On Fri, 17 Jan 2003 16:00:00 +0000 (UTC), "W K" <[email protected]> wrote:

>
>"(Pete Cresswell)" <[email protected]> wrote in message news:[email protected]...
>> Just saw a post on alt.mountain-bike ("Foes Customer Service - someone
>else
>> doin' it right") that contained the statement:
>>
>> "Believe it or not, if ridden off-road for that long (minimum it seems 5 years) just about any
>> aluminum frame will break."
>>
>> I've heard others say that this is nonsense, but source seems pretty
>reliable.
>>
>> OTOH, airplane frames last a lot longer than 5 years...
>
>Find out about the DeHavilland comet, the first passenger Jet.
>
>Early attempts to do things don't always work properly.
>
or the DC-3 ... for the other side of the same coin...

 

[Mike Jacoubowsk]

> It is ******** plain and simple... Aluminum as a material is a fine choice and can be as durable
> as anything else. Any short life is due entirely to either poor design or poor construction ...
> and Aluminum is not the only material with that problem.

Not always a result of poor design or poor construction, but rather a choice made between being
stupid-light and long-lasting. When you get aluminum road frames under 2.5 lbs, you're taking the
material to the edge, plain & simple. It's a choice that people can make (do I want something
stronger and a bit heavier, or do I want the lightest thing made?) if they wish. As long as the
manufacturer makes people aware of that choice, then at least some of the responsibility for its
short life lies with the purchaser (who created a demand for the product).

And this doesn't apply just to aluminum. Could be steel, ti or carbon. Any material can be taken to
the edge, to make something a bit lighter, but at the expense of durability. There could be poor
design or construction responsible for failures, but that's a secondary issue. Primary is a
willingness to trade off durability for lightness, and that decision is made by the consumer who
buys it. If people weren't willing to buy something that has a 30 feet/30 second warranty (whichever
comes first), manufacturers wouldn't build the stuff.

--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

"ajames54" <[email protected]> wrote in message
news:[email protected]...
> On Fri, 17 Jan 2003 15:12:27 GMT, "(Pete Cresswell)" <[email protected]> wrote:
>
> >Just saw a post on alt.mountain-bike ("Foes Customer Service - someone
else
> >doin' it right") that contained the statement:
> >
> >"Believe it or not, if ridden off-road for that long (minimum it seems 5 years) just about any
> >aluminum frame will break."
> >
> >I've heard others say that this is nonsense, but source seems pretty
reliable.
> >
> >OTOH, airplane frames last a lot longer than 5 years...
> >
> >Comments?
> >-----------------------
> >Pete Cresswell
>
>
> It is ******** plain and simple... Aluminum as a material is a fine choice and can be as durable
> as anything else. Any short life is due entirely to either poor design or poor construction ...
> and Aluminum is not the only material with that problem.
>
> Or it could be an industry that is working to convince you that you need to replace your bike far
> more frequently that may ever be necessary ... hmmmm.

 

[Tom Arsenault]

"W K" <[email protected]> wrote in message news:<[email protected]>...
> "(Pete Cresswell)" <[email protected]> wrote in message news:[email protected]...
> > Just saw a post on alt.mountain-bike ("Foes Customer Service - someone
> else
> > doin' it right") that contained the statement:
> >
> > "Believe it or not, if ridden off-road for that long (minimum it seems 5 years) just about any
> > aluminum frame will break."
> >
> > I've heard others say that this is nonsense, but source seems pretty
> reliable.
> >
> > OTOH, airplane frames last a lot longer than 5 years...
>
> Find out about the DeHavilland comet, the first passenger Jet.
>
> Early attempts to do things don't always work properly.

I wouldn't call it ******** really. Aluminum does have a finite life in fatigue motions and
movement. Improper joining techniques and heat affected areas during welding will make this an
almost definite. Look it up in Mark's Standard Handbook for Mechanical Engineers. Fatigue resistance
of aluminum is a lot less than steel or titanium. That's just the property of the material. Aside
from that; who wants to ride the same bike for over 5 years? That's no fun.

Tom "A Licensed Professional Engineer"

 

[Mike Jacoubowsk]

> Others who ride aluminum bikes have commented to me how after a few years the stiffness that was
> present when the bike was new seems to go away.

Nobody's been able to show that actually occurs, despite years of trying. I think it's a
psychological effect; after a while, you start to focus on things you might not like about your
bike, and they start becoming more and more real in your mind. It's like that printer you got that
was lightning-fast when new, but now it seems to be the slowest thing in the world. The printer
hasn't changed, just your expectations and desires.

As Jon pointed out, the myth about frames going soft was a big one back in the days that everything
was steel. We all believed it, especially the racers. At some level it's an ego thing... after all,
a wimpy rider isn't going to have an effect on a frame, but me? I'm sure I can tell it's no longer
as good as it once was, which obviously means I'm an incredibly strong rider, pushing the poor
bicycle to its limits.

--Mike-- Chain Reaction Bicycles http://www.ChainReaction.com

 

[Ian S]

"W K" <[email protected]> wrote in message news:[email protected]...
>
> Find out about the DeHavilland comet, the first passenger Jet.
>

Actually a fascinating story. A deadly combination of metal fatigue coupled with crack initiators
(the squarish windows - see: http://www.geocities.com/CapeCanaveral/Lab/8803/comet.htm)

 

[Almost Fast]

Materials class? Aluminum not a good spring? Aluminum forks don't return after small deflections?
Frames go soft? And this is "obviously" subjective?

No offense, but if I were you Tom, I'd ask for my tuition back.

[email protected] (Thomas Reynolds) wrote in message
news:<[email protected]>...
> "(Pete Cresswell)" <[email protected]> wrote in message news:<[email protected]>...
> > Just saw a post on alt.mountain-bike ("Foes Customer Service - someone else doin' it right")
> > that contained the statement:
> >
> > "Believe it or not, if ridden off-road for that long (minimum it seems 5 years) just about any
> > aluminum frame will break."
> >
> > I've heard others say that this is nonsense, but source seems pretty reliable.
> >
> > OTOH, airplane frames last a lot longer than 5 years...
> >
> > Comments?
> > -----------------------
> > Pete Cresswell
>
> My comments are limited. I don't claim to be an expert. I am a roadie who puts in 6K-10K miles per
> year and all but one of my bikes are steel. The one that is not is a new aluminum bike that I am
> still putting together.
>
> From my materials class in college I learned that aluminum is not a good spring. Consider a road
> fork as an example. As you travel down the road every small bump causes a small deflection. A
> steel fork is very good about going back to its original position. An aluminum will never quite to
> that. It should be possible to wear out an aluminum bike, not break them.
>
> Others who ride aluminum bikes have commented to me how after a few years the stiffness that was
> present when the bike was new seems to go away. Obviously this is subjective but I expect my new
> aluminum frame to need replacement in a few years.
>
> Tom

 

[David Damerell]

Tom Arsenault <[email protected]> wrote:
>I wouldn't call it ******** really. Aluminum does have a finite life in fatigue motions and
>movement.

A solid granite doorstop has a finite life if left outside in the wind and the rain, but I wouldn't
worry about it wearing out for all that. This is an almost meaningless statement unless one
quantifies "finite".

>just the property of the material. Aside from that; who wants to ride the same bike for over 5
>years? That's no fun.

Eh? It was a good bike 10 years ago; it hasn't changed any since.
--
David Damerell <[email protected]> Kill the tomato!

 

[Mike Jacoubowsk]

> I just get tired of people blaming the material for what are really design/marketing decisions. It
> does a great disservice to all those builders who build a durable / reliable product...

I agree. It's not the material, it's what you do with it. As I've said before, you could probably
engineer a nice-riding bike out of bamboo if you had to.

--Mike-- Chain Reaction Bicycles http://www.ChainReaction.com

"ajames54" <[email protected]> wrote in message
news:[email protected]...
> On Fri, 17 Jan 2003 18:28:45 GMT, "Mike Jacoubowsky" <[email protected]> wrote:
>
>
> >How strong is strong enough? How light is light enough? Different
answers
> >from different people. Your answers sound like they'd mirror mine, but
it's
> >a personal choice. When it's not presented as a choice, when people are told that a 2 pound frame
> >is as good as anyone needs, *then* I have an issue.
> >
> >--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com
> >
>
> I just get tired of people blaming the material for what are really design/marketing decisions. It
> does a great disservice to all those builders who build a durable / reliable product...

 

[Jobst Brandt]

Mike Jacoubowsky writes:

>> I just get tired of people blaming the material for what are really design/marketing decisions.
>> It does a great disservice to all those builders who build a durable / reliable product...

> I agree. It's not the material, it's what you do with it. As I've said before, you could probably
> engineer a nice-riding bike out of bamboo if you had to.

http://www.bicyclemuseum.com/html/bike5.html http://liegerad.franken.de/bilder/spezi2001/17.html
http://www.c1biker.com/nuke/modules.php?name=News&file=article&sid=102
http://www.dursley-pedersen.net/tra.shtml http://www.ottavia.com/bike_catalog.html
http://www.saffron-ventures.com/personal/woodbikes/homepage.php

Jobst Brandt [email protected] Palo Alto CA

 

[Jobst Brandt]

Mike Jacoubowsky writes:

>> I just get tired of people blaming the material for what are really design/marketing decisions.
>> It does a great disservice to all those builders who build a durable / reliable product...

> I agree. It's not the material, it's what you do with it. As I've said before, you could probably
> engineer a nice-riding bike out of bamboo if you had to.

http://www.americanbamboo.org/GeneralInfoPages/BambooBicycle.html
http://www.vagabondimports.com/bike.htm

Jobst Brandt [email protected] Palo Alto CA

 

[Mike Jacoubowsk]

> http://www.americanbamboo.org/GeneralInfoPages/BambooBicycle.html
That's the bike I want! A real bamboo frame. According to the author, "It is beautiful, light and
fast - and it is nice to touch."

"Every bamboo must be selected and fitted into the frame according to size and quality. The secret
lies in treating and handling the material the right way."

> http://www.vagabondimports.com/bike.htm
Nah, just a steel frame with rattan wrapping. Might as well put carbon-fiber decals on one!

--Mike-- Chain Reaction Bicycles http://www.ChainReaction.com

 

[David]

"Jon Isaacs" <[email protected]> wrote in message
news:[email protected]...
> Well said Mike. One factor to remember is that if one is designing a super light throwaway bike,
> Aluminum is indeed the material of choice simply because one can make a lighter frame from
> aluminum than just about anything else.

Agreed.

> In otherwords, if one is going to design as light a frame as possible and is willing to make a
> throwaway frame with a limited lifetime, then aluminum is the material of choice.
>
> On the otherhand, if one is going to build a stiff and strong frame that will last forever with a
> heavy load and a heavy powerful rider, aluminum is probably the best choice as well.

I agree that it's a good choice. I wouldn't say "best", but that's a judgment call.

> It is important to understand just which of these two frames one is choosing prior to purchase.

If only it were that simple. Aluminum seems to be the material of choice for a fair number of
high-end, heavy-yet-fragile frames as well. I've seen heavy-yet-fragile steel bikes, but only
very low-end.

David

 

[Jose Rizal]

Jon Isaacs:

> The issue with aluminum is fatigue. In theory and loading and unloading of an aluminum component
> will cause any pre-existing crack to slightly grow. Eventually that crack will grow enough to
> cause failure.

Is this similar to stress corrosion cracking? Quite a few MtB cranks and chainrings being sold at
the moment are made of 7075-T6 and 7050 Al, which has poor SC resistance and requires a protective
coat (paint, anodising). Are the alloys used in bike frames of a different kind/temper? And what
does it say for those cranks and chainrings made of 70xx series Al?

 

[Jon Isaacs]

>I know nothing about the differant types of aluminium alloy - do they have different fatigue
>characteristics? My cycle is plain guage aluminium and defined as 7005 HT.

They do but not greatly. The issue is how they are designed and manufacturered. Are they
sufficiently overdesigned to keep the stresses low enough to avoid fatigue issues? That is
the question.

Now steel and titanium have endurance limits, that is, they will not fatigue if the stresses are
kept sufficiently low. Lightweight (stupidlite) steel frames are significantly more likely to
fatigue than an equal weigh aluminum frame.

I say this: Pound for pound, one can build a bike that will be have fewer fatigue problems from
aluminum than from steel.

The fatigue problem in AL bikes exists because some very light frames are possible is a limited
fatigue life is acceptable. This is a design issue and no designer is foolish enough to design a
steel bike with those sorts of lifetimes because the bike will still be "heavy."

Jon Isaacs

 

[S. Delaire \"Ro]

Pete Before taking up bicycles full time I worked for NASA as a tech. My primary role was as a
T.I.G. welder but was also certified for bonding (glue) and riveting. We made high tech parts from
all materials. NASA rates all structures and for that matter all projects by a "percentage of
success". They concluded that there is no 100% way to join aluminum. Done in the best environment
and procedures it can only come to 98 percent, which in my mind means 2 out of every 100 bicycle
frames will fail. Aircraft are REQUIRED to have routine inspections and are repaired routinely. How
many bike riders routinely inspect their bikes for cracks? Passenger aircraft usually are rated for
20 years service. Fatigue life for aluminum is known to be shorter than other common materials.
Steel and titanium can be joined to 100% reliability. Done properly. Joining composite structures is
also problematic and not able to achieve 100% success. Aluminum is cheap, abundant, light and easy
to form, weld, and bend, important in keeping the cost down for mass production. Titanium, on the
other hand is certainly the toughest. It kills the cutting tools quick, and is hard to bend.
Properties that seem nice to have on a bicycle. Steve "Speedy" Delaire

"(Pete Cresswell)" wrote:

> Just saw a post on alt.mountain-bike ("Foes Customer Service - someone else doin' it right") that
> contained the statement:
>
> "Believe it or not, if ridden off-road for that long (minimum it seems 5 years) just about any
> aluminum frame will break."
>
> I've heard others say that this is nonsense, but source seems pretty reliable.
>
> OTOH, airplane frames last a lot longer than 5 years...
>
> Comments?
> -----------------------
> Pete Cresswell

-----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1
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[x]

RE/
>Anecdotal evidence; my son's aluminum Gary Fisher (pre-Trek) is at least ten years old. Still
>going strong.

Another anecdote: it only took me about three years of hard road riding before the rear triangle on
my Panasonic road bike came apart where the the rear dropouts connected to the frame.
-----------------------
Pete Cresswell