bobbyl1966

How many years is the life of carbon fiber life and aluminum bike. I see one post online and say carbon fiber bikes have life 3 years. Why is that? Why carbon fiber bikes have so little life. Aluminum bikes what is that aluminum fatigue what happens to the frame. How many years is the life of aluminum bike.

Homebrew01

Nonsense. Most any frame of any material, will last many decades unless crashed, or has a very rare defect.

mrv 

Howdy.
Frame life is related to how it's used. If I leave a carbon bike hanging in my basement for three years, it'll be fine three year later. If some 250lb weight lifter sprints everyday on any bike, he'll put it through stress cycles to fatigue it eventually.

The reason the different material have different recommendations are for 'frame life' is related to the material properties.
Here's some stuff to look at: https://en.wikipedia.org/wiki/Ultimate_tensile_strength
- Look down the table at the 4130 steel. A typical frame material. The "YIELD" is the strength where a material goes from elastic to plastic. Going into the plastic region means your frame just bent. So your steel frame yields at 951MPa (a number indicating force x area). If you reach the ULTIMATE number, your frame just broke. Bummer. Notice the number is higher than aluminum. 1110 MPa for steel.
- Now look at aluminum. Yield at 414MPa, Ultimate at 483MPa. You might be thinking - dang, those numbers are lower than steel, AND closer together than steel. I should get a steel bike! Well if you like steel. But what the numbers mean is you need more AREA for your aluminum bike tubes. That's why CANNONDALE made the tubes so fat way back when. And the steel bike tubes were smaller. The bigger tubes are less flexy, so aluminum got the reputation as a "stiff" ride.

- Now! What about carbon fiber? Look down the table some more until you see the graphene / carbon nano tube / glass numbers. I have no clue which of those apply to bikes. But for this post it doesn't matter. All I want you to look at is the yield number: N/A As in not applicable. It doesn't bend - BUT MAN! LOOK AT THOSE ULTIMATE NUMBERS!!
So super light bikes. Super strong. Just a reputation for breaking like glass. No bending.

But wait, there's more! You asked about life. All I talked about was yield and ultimate strength. CLICK HERE: https://en.wikipedia.org/wiki/Fatigue_limit
There a plot showing STRESS vs CYCLES (S -N Curve). It indicates how many cycles of a given stress a material can take. So the big guerrilla sprinting everyday applies really high stress loads. The high stress loads limits the number of cycles you can apply - you have to stay BELOW the S-N curve, or YOU FAIL! bummer.
The guy biking to work everyday and just sits on the bike and pedals, no so high stress loads. He rides his bike for 20 years and never has a stress failure.
Steel is higher than aluminum, but that applies to THE MATERIAL - not necessarily your bike. An aluminum, well designed, will last 30 years - I had a Cannondale touring bike from the 80s. Would have kept it but it was small.

Carbon fiber can take really high loads, so if well designed, well built, I'd ride it as long as it's not damaged. I think the coatings used now days also protect degradation to to sunlight - that could have been another 3-year limit thinking.

Let me know if all that helps. And correct anything I got wrong.... or... everything I got wrong.

Andrew R Stewart 

So much of the bike industry has in it's best interests to sell you a bike every few years, not let you service it and keep it current. So many of the voices that talk about life spans, performance and such are (here it comes...) from the bike industry. Additionally the design and application of a material might not be chosen to have a longer life as opposed to, say, a lighter weight. So to take a material apart from the application is only talking about the lot the house is built on and says little about the life span of the house. Andy.

Siu Blue Wind

Awesome post.

taras0000

@mrv and @Andrew R Stewart nailed it. You can't just look at the material in and of itself. The engineering/design that goes into a frame is going to be more important than just the frame material itself. You can make a stronger aluminum bike than a steel one if the steel one is poorly designed. A lot of the myths relating to frame material are from decades ago as well, when there wasn't much engineering knowledge available for aluminum, carbon, and titanium. The material advancements also didn't exist at the time. Steel was a much more refined product than the others 20-30 years ago when a lot of these "misconceptions" were true, and this these stereotypes gained traction fairly quickly. Now all these materials are fairly refined and one can choose a bike of any material to suit any application they choose.

prathmann

True, but note that you can increase the area by either using larger diameter tubing (as in Cannondales and Kleins) or by using tubing with thicker walls (as in the earlier Alans and Vitus'). The thicker tubing with standard outer diameter led to the early aluminum bikes having a reputation for being light but excessively flexible or whippy. Only after Klein promoted the use of larger diameter tubing did the stiff reputation get started - another example of the ride characteristic being a function of the design rather than inherent in the material.

As for the lifetime, I've only had one aluminum bike. It's currently 27 years old and is nearing 150,000 miles. I'm hoping it still has many years to go. I have yet to have a steel bike go that far without a failure.

mrv 

My touring-Specialized RockHopper is circa 1990. It was given to me. I have no idea how many miles are on it. I'm thinking very few, so i'm fine riding it for many more years.
I had to retire a custom race bike due to corrosion. Steel. It rusted from the inside out. One thing I like about steel, I had LOTS of warning a failure was coming. Under the power coating I could something bad was happening. And I know that's the same reason people prefer aluminum. I suspect a well built / designed aluminum frame would give warning cracks before failure. INTERESTING TO NOTE! A friend pretty much gifted me a Cannondale MTB he was told was cracked. I used most of the part to refurbish a GUNNAR Rock Hound. I then stripped the paint off the Cannondale, and no crack. I've powered it after polishing. Now it's a kind of smoked chrome look. I'll build it up eventually.

Some photos here:
LOOKS LIKE A CRACK - near the Cannondale head tube. I got no photo of the paint stripped.

Here's a photo album. https://goo.gl/photos/om6FUVuHkAqnqpR18
It contains after / before pics of the GUNNAR. Look real close at one of the stripped bottom bracket photos. You can see pitting through the chain stays. I have decided to let it go, keep an eye on it. Make it my bike, not my son's. That's steel - it does corrode.

Cheers!

ps - yes. i dissolved the GUNNAR seat post out with lye. lye dissolves Al. No harm to Fe.

busdriver1959

I got my first nice custom steel race bike in 1980. It wasn't long before somebody (who wanted to sell me a new bike) told me that it should be replaced after 5 years. After 16 years of racing, I did replace it but it wasn't done. It stayed in the lineup for many years after that. It isn't currently built up but may be back in service some day.
It's probably best to decide for yourself when you need to replace any of your possesions. Don't let a salesman make a decision like that for you.

fietsbob

As the consumer of Carbon composites wants to stay in the avant garde of materials science and the latest component upgrades.

after a few years the cutting edge is Moving away from them so they have to buy a new one to keep up with the Joneses.