Hydrated

Wow. We usually hear this about carbon bikes.

But you're saying that your steel frame rusted apart out in the boonies so quickly that you couldn't prepare for it? Steel has the most gentle and gradual failure mode of any of the materials that you mentioned. Carbon has the least tolerance for sustaining damage and continuing to be reliable.

From a purely engineering point of view, you have this backwards.

Weatherby

I am an engineer. I was not speaking theoretically but empirically. I am saying that during a long tour, on a particular day, I stood up to jam a hill in the deserts in California and the downtube broke. I disassembled the Bottom Bracket and could see some rust inside despite liberal use of grease inside. This frame saw a lot of service in the rain and probably got 30-40k out of it.

I have a carbon framed bike with probably close to 100K on it ridden in all kinds of conditions. Had this one suffered a similar failure, I could have repaired this easily myself in the field. Try repairing steel. Or try finding someone who can. You can't just weld a 0.6mm thin tube. The main tube would have needed to be replaced entirely and repainted, which is not what I would consider useful as a repair. In my specific case, I could not find a place to repair the tube quickly (LA) or in a cost effective manner. Air freighting an aluminum frame was my solution. This Klein aluminum framed bike actually spent 30 straight days touring and camping in the rain every single day with no worry about rusting away. I usually chuckle when cyclist think they can easily get their steel framed bike fixed or they say steel fails in a non-catastrophically. My ferrous seat post bolt fatiqued and I woke up with a swarm of people around me and next thing, I was on the way to the ER. So, steel gets no love on my bike.

Hydrated

Me too. 30 years working with aircraft where people die if engineers make mistakes.

This is anecdotal, not empirical. If you like carbon fiber... that's fine. Ride it. But don't mislead others by stating your opinions as scientific fact. I'm glad that you edited your original post, I guess that you realized that it was just silly sounding. But your edit isn't much more logical. As a material, steel does fail in a more gradual way that is more detectable beforehand. Your comparing a steel seatpost bolt to a steel frame is just silly. A seatpost bolt represents a single point of failure in which the bolt is under extreme torque and elastic tension. This sets up failures that are sudden and catastrophic. A frame rarely sees such forces... steel or otherwise. Comparing the bolt to a frame is like comparing apples and watermelons.

I'm not one of those guys who runs around warning folks that their carbon bikes are going to self destruct... they are plenty dependable when cared for properly. Just like a steel bike is plenty dependable when cared for properly.

Homeyba

I'm not an engineer but I played one in a movie...

We could go off into the "this material is better than the other" argument again but I think that has been already covered ad nausium. The different materials each have their advantages and disadvantages but the truth of the matter is that they've all proven to be more than adequate for long distance use. In my years of ultra-distance riding and racing I've broken a steel frame, an aluminum frame and a titanium frame. I still would (and do) ride them.
The smart consumer is going to look at what he/she wants the bike to do and buy the frame that will do that job. Worrying whether it will break catastrophically is a waste of time.

Hydrated

You are quite right, sir.

I apologize ladies and gentlemen of the LD forum... I fell into that age old trap:

lhbernhardt

I had the seat tube break recently on my Rodriguez fixie (80,000+ km on it). When I returned it to R+E in Seattle for the lifetime warranty repair, I took the opportunity to change a few minor things. One of them was replacing the brazed in seat tube pinch bolt tab with a plain slotted seat tube to take a separate collar. The seatpost bolt tends to be for me a pretty vulnerable part of the frame. You can't help but overtighten the sucker, which bends the tabs slightly, causing the bolt itself to bend slightly. After a few times tightening and loosening in order to pack the bike for air travel, the bolt breaks, usually when you're in Maui or in some small Italian village, and nobody has a steel M6 bolt, so I had to borrow one from my stem (good thing it uses 2!) for the duration! Now I carry around a spare seatpost collar with bolt, and I'm good for many more airline trips!



BTW, I could tell something was going to happen to my steel frame, so @Hydrated is right; I could hear strange creaking noises that I couldn't figure out, until the tube just decided to snap. But you can still ride a frame with a broken seat tube, as long as you're gentle. The guys at R+E couldn't figure out what would cause the tube to break where it did (about 2/3 the way up the seat tube). No inordinate signs of rust, other than where the tube had started cracking.
@Weatherby is also right; cf can easily be repaired, as long as it's not the fork. There's a guy in North Vancouver who builds competitive sailboards and stuff; he does a great job repairing carbon frames. He also fabricates carbon handlebars & stems for Canadian National track team riders. I think you'll see more builders who are able to do this as the material becomes more prevalent.

Luis

Weatherby

I edited my post to correct spelling errors, silly me.

I will take my two data points as empirical evidence that steel is not infallible; nonetheless, I would only use steel for load bearing fasteners on the bike. I provided personal experience, there was nothing scientific in my post. If anyone read my post otherwise, I can't help them.

My point was not made on a professional basis nor scientifically made nor was I suggesting carbon fibre, I was giving my experience countering the tired old saw that steel frames can be fixed. I'd like to hear from someone who had a frame welded back together in a situation like I had. I''ll take aluminum on a touring bike for reasons given. I just remembered, I had a rack brazon break on a steel bike but I managed to make that work w/o a repair. But, the steel failed. So, that is three instances in my experience. You might think they are silly but when and where they failed were quite serious as in I could have died.

If carbon fibre is so evil, why is it used on planes, race cars, Ferraris, etc. Even spend 15+ hours on an A380, so quiet and comfortable, and the restrooms and showers are fabulous.....thanks to light and strong composite.

The main problem with carbon fiber frames is unrealistic consumer expection and demands for sub 800 gram frames coupled with lousy engineering and even poorer processing in China.

Wilfred Laurier

of course not
you just started your post saying that
you are an engineer
and
your conclusions are based on empirical evidence

i have a sneaking suspicion that you have an engineering degree
but do not actually work as a peng
if i am wrong...
:-O

Bandera

Those restrooms may be OK for touring but if you want high performance aircraft loos there is nothing like the old school C&V Concorde WC.

-Bandera

Hydrated

I don't even want to ponder the results of a catastrophic toilet failure at Mach 2...

Homeyba

It'd probably leave a heck of a brown streak!

Weatherby

But walking in the isles was hard. Not much headroom.

Nothing like having a real urinal on a plane with a sofa chair in the loo with a shower to boot. Doubt this would be feasible without carbon fiber. F-22? Made from steel, right.

Steel rusts. Wait, I apologize. I need scientific evidence for that.

k7baixo

+1.