In regards to this particular bicycle, there's no possible way for us to determine the direct cause of the OP's frame failure. All we can do at this point is speculate and discuss possibilities. The scientific data suggests that his frame failure was most likely, due to fatigue. How you can state unequivocally for certain, that it was not, is beyond my comprehension. Speculation always favors science, not anecdotal testimony.
We don't have any scientific data in this case; we have one anecdotal story.
We have one description of one guy's seat tube that broke in an area that doesn't see the typical kind of cyclical stresses required for fatigue failure, and in an area where the rare failure is almost always due to damage. We also have the description of a "clean break", which is also not a characteristic of fatigue.
Now if the OP is somehow especially hard on seat tubes, then steel would probably be a better choice for him anyway, but that's because it can handle more damage before it weakens.
You can try Public and I believe Linus as well.
Cyclical stress comes in the form of vibrations. The entire bicycle frame vibrates.
Last edited by WestPablo; 05-22-14 at 02:31 PM.
Google up photos of broken seat tubes -
Here's the first one that came up for me - this is fatigue, down at the bottom tube where stresses are concentrated and cyclical, and pre-existing damage from welding can be present.
They're almost ALL at the welds (or lugs) - either BB or top tube joint. Hardly any aluminum ones in my results.
Or else they're the result of obvious damage or misuse (seat post insertion length issue).
Undamaged seat tubes simply do not fail in mid span from fatigue... aluminum or otherwise.
Last edited by DiabloScott; 05-22-14 at 04:03 PM.
I had no idea they weren't making steel bikes anymore! My trusty 1996 GT Outpost, with a zillion miles on it, is going to fail me SOME day. Does this mean my next bike is going to have to be aluminum?
"I just need a rest...and by 'rest' I mean a really long bicycle ride."
That's all BS. Ti is stronger than steel,rides just as well,and can be about as light as alum.
"I still hold that a modern steel bike built with hand-made cross-three wheels and good tires inflated to a maximum of 110 psi remains the gold standard. No other bike will ride as well."
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If it broke clean it must have been improperly welded or improperly formed into a tube at the factory. I have seen alu and steel get shear breaks due to improper cooling, including 3 inch thick bar and pipes with quarter inch wall thickness that had just been installed or mid-installation.
I am guessing it is a forming defect from factory, not welding, and not seat mount height.
I can't wait for the next pint of good chocolate milk after a long ride.
Yep. I chose communication over science. Not much we can extract from the over simplified chart. (nor from the OP case neither)
I have a graph just for you
The fatigue life for carbon fiber isn't infinite but roughly just higher. (depends on which one though)
Even then there is lots of factors to take into account. What about the type of process used, build quality, frame design, under which load the bike is and where, how old the bike is (a 1976 steel bike vs a 2012 carbon bike), freeze-thaw cycle, riding type, corrosion resistance, shocks/cracks...
Probably the reason why in real life, it seems that there is some catastrophic failures on the carbon fiber side as well. I was reading a thread not long ago that was asking a good question: why isn't much touring bikes made of carbon fiber?
I was reading something recently about graphene that supposedly is better than anything else on the market (carbon nanotubes included) but isn't in real life due to imperfections than come with the current process used.
Last edited by erig007; 05-22-14 at 07:18 PM.
I have 2 steel framed bikes and one aluminium...My aluminium MTB has been beaten to death and it just keeps coming back to life.
You guys are making me flash back to my metallurgy days. STOP IT.
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So I agree about the user being at fault and not the frame. but that doesnt really matter any more does it.
check this out, steel frame, carbon fork, 105
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