janiewilson3 <> programmer

I heard a quote from cycling TV that someone like boonen would get 10-12 frames a year. I'm sure someone can find the exact quote, I think it was said during the E3 race.

The Trek and Specialized aluminum lugged, carbon tubed frames were readily available, circa 1990-94.

Once again opinion gets confused with fact. After a statement like that I would question any other things he has said and perhaps ignore him...

Where do people get this stuff? Incredible. Every material that is put under stress experiences strain. Strain is the deformation of the material (bending and torsion in a bike frame). When you put many strains on a material it is possible for that material to fatigue. The amount of fatigue has a great deal to do with how close to the ultimate failure of that material the strains in question are. So (duh!) the lighter the bike made from the same material, the more likely fatigue will be an issue. That's if proper engineering were not a factor, since poor engineering concentrates stresses and thus decreases the fatigue life.

All that being said, here is the fatigue life of popular bike frame materials, from best to worst: carbon fiber, titanium, steel, aluminum. Steel and titanium are very close together, perhaps indistinguishable, however titanium has greater notch sensitivity. Carbon fiber laminate is also notch sensitive. In other words, inspect your frame for dings. Of these materials, only aluminum has no limit below which it does not fatigue.

You might want to visit:
http://en.wikipedia.org/wiki/Metal_fatigue

The takeaway: your LBS is a commercial enterprise. The mechanic/salesman thought he could sell you a set of wheels more easily and sooner than a carbon fiber bike. As a salesman, sometimes you have to make the call and then stick with it. If you're running the same wheelset that came on your Litespeed, and you keep them maintained, you don't need another wheelset, either.

Equipment is like 3%. Nutrition is like 5%. All the rest is training. Guess where you should put your money and time to get the best results? I know, numbers like these are just for disputation. But it's not entirely a joke.

Carbon is used successfully to build the Airbus planes.

For example, this plane:
Airbus A300B4-605R
American Airlines Flight 587
Belle Harbor, New York
November, 2001
Casualties: 265
Circumstances: Carbon fiber vertical stabilizer and rudder separated from aircraft.

http://www.brojon.org/images/587tail.jpg

http://observer.guardian.co.uk/inter...ticle_continue

Well that's the last time I take my bike up to 600mph, I'll tell ya that much... :rolleyes:

How many other structural failures have there been in aircraft where CF wasn't used? Are you implying that there were no structural failures in aircraft, EVER, until this one? Hmm... I can recall one off the top of my head. It was an Aloha airlines 737 whose roof blew off because of stress cracks in... you guessed it... Aluminum.

Yeah but that was because.....it um...... see what happened was.......Alright you got me.

and it looks more like is was a bonding failure than the carbon flat out breaking... but i'm not really qualified to make that kind of assumptioin. so i'll just leave it as pure speculation based on nothing but a news picture.

A car wears out in 4 years?

Carbon fiber by itself isn't gonna be the weaklink...its the matrix material.
That clear stuff that keeps the fibers together is the matrix, usually epoxy or some unhealthy concotion thereof. This stuff absorbs water and swells, degrade in direct sunlight, expands and contracts alot due to temperature changes (while the carbon fiber iteself is basically neutral to thermally induced strain (elongation))

So after a while (depending on where you ride or how its cared for) the matrix will eventually degrade/crack/debond from the fibers.

just the way it goes with any fiber reinforced composite material.....just like crack propagation (fatigue) are just the realities of metal alloy materials...

In reality, who cares if a 50 year old CF bike isn't what it used to be when new...I don't.

yeah...we worked this particular AA crash. The parts were sent to us at NASA Langley (head of composite structures in US) for the post mortem.

Carbon fiber gets blamed again.....why?

Because idiots don't know how to use it. (PERIOD)

Sick and tired of CF being blamed for failures like this...its the workers who decided "hmmm, lets use rivets instead of the glue that we're supposed to use"....good call, the rivets creates stress concentrations that causes cracks to initiate. Once initiated the, the crack grows due to cyclic loading and eventually breaks off. Is that carbon fibers fault??? According to CNN and the general public...it is!

hah hah So I was right!

I have seen in several places that manufacturers allot five (sometimes more) frames per rider on pro teams (plus TT frames). That would work out to about 6K miles per frame using your number. Interesting. Coincidence?

Many, with the Comet being, perhaps, the most famous.

10 points! Another 10 for further explanation of fatigue durability limits.

That's a pretty big generalization given the many different design and layup details for different CF frames. I think the argument is based on some of these well-publicized failures.

It is fair to say that not every composite frame will last for ever. I want to involve the logicians as well.....

Wikipedia is hardly an accurate source of reference for anything. I agree with the rest.

Back to the OP: time has proven these myths to be false, there are thousands of old Trek OCLVs out there and hundreds of thousands of old Cannondales, and millions of bikes >20 years with intact aluminum cranks and rims (the dirty truth to aluminum bashers).

The whole metal fatigue concept is theoretical, and a practical non-concern. Somehow, guys that quote the fatigue of aluminum suggest that this only applies to frames, and not other aluminum components. In the real world, do a search even on this forum, and you will see more references to broken titanium parts than anything else. There is a big tendency of Ti builders to under-engineer the frames, and the inherent flex in ti is a big problem for heavier riders and frame integrity.

EFBe testing shows that some aluminum frames are much stronger than any titanium frame tested, and the strongest frames tested to date at 200,000 duty cycles are carbon. Regardless, in the real world, of even professional riders, any typical good mass produced frame will last a lifetime.

The only real, practical advantages of Ti are corrosion resistance and ability to withstand high heat, for those risking burnup on re-entry. However, handling on ti frames is a big issue above ~175 lbs.

While this is true, don't pro cyclists use several bikes in a given year?

I still wouldn't ride carbon at my weight, but see nothing wrong with it as a bike material for you light weights (light weight being defined as any non-clydesdale).

Suit yourself. 240 lb Clyde here. Lemond CF frame, 8+ years, ~ 30K miles. :)

Errant comments on CF aside, I suppose the other issue up for debate in the original post is new wheels vs. new bike.

If the OP's Litespeed frame is still in good spec, might s/he be better off using that $3000 or whatever on a pair of really sweet wheels (as noted by this naughty LBS sales associate) rather than a whole new bike? I would suggest quite possibly yes. If it's a nice frame as it is, spend the cash to upgrade components (new wheels, replace worn derailleurs, STI lever upgrade, cool colour bar tape, etc.) rather than buying a whole new bike - s/he will probably end up with a nicer ride than could be had with spending that cash on a complete bike. (the existing wheels could be kept for training)

Thoughts?

Many read it on places like (drumroll please).....Bikeforums. Well meaning people with not enough knowledge adding to discussions as if it's a fact.

On your second sentence...basically you are saying (with the double negative out) that aluminum has a limit beyond which it will fatigue. Correct?

Well, NASA's shuttles are wrapped in composite tiles, which, as we all know, crack and fall down all the time.

Russian spaceships are made of good old titanium.
And it can be reused. What are titanium frames made from? Russian scrap metal.

http://www.eurasianet.org/department...images/sj9.jpg
http://www.eurasianet.org/department...mages/sj10.jpg

My 2300 was not a problem. I subsequently sold that Trek to a friend WHO STILL RIDES IT. And FYI, the earlier bikes did NOT have 'bright green decals'. That came later.

Nobody said anything about OCLV. We're talking CF here. And the 2300 was mainly CF. 20 years ago.

No, I'm saying that aluminum will fatigue at any loading, however light, alone among bike frame materials. That's why aluminum frames tend to be heavier than one's calculations might suggest. They overbuild them to allow for fatigue. Practically speaking, one of the above posters has it about right: we should all live so long and ride so much as to wear out our bike frames! Yeah, try to wear your frame out!

Carbon frames also come out heavier than calculations might suggest because in the practical world it's hard to engineer and build them with the fibers all oriented in the most efficient direction. Carbon is actually the best material for Clydes. It's so easy to make it stiff enough and still very light.

:rolleyes: Oh yeah...like they don't have something to sell you! Those sites are hype city! If they can't effectively make you dissatisfied with the stuff you currently have, they won't be able to get into your wallet. And that IS why they exist.