only thing this is an example of is hitting a curb at high speed. Maybe in a crit or something. Hit so hard he snapped the fork below and above the head tube. This impact would have effed anything.

Actually, steel does snap, and aluminum does bend. But that's not important. What IS important is that bending is WAY overrated as a safe failure mode. That, I am sick to death of almost more than anything. Bending isn't some benign and gentle form of failure, and it certainly does count as failing "catastrophically" under the right circumstances (which are quite rare for both steel and aluminum).

Again, experience tells me otherwise. I've done my share of time working in a couple of different bike shops, and saw enough broken bikes to have some idea of what I'm talking about.

I've seen plenty of aluminum frames with dents and bends from smacking into things. If it's dented or bent in a non-critical area, like in the middle of a tube, it's no bigger a deal than with steel. As I already said, the stuff DOES bend. And again, there's just no reasonable way to argue "if I had been riding aluminum I would have been injured much worse." Chances are good that you're wrong about that.

Now, I've never ridden an aluminum fork into anything because, like most people, I've never ridden an aluminum fork at all. They're relatively uncommon. I have no experience with how most of them fail and can't say anything about it. But I've ruined two steel forks in the course of two months before, and they broke very differently. One was a leg cracking off from fatigue, and it WAS an abrupt failure from my perspective - the fork went from no noticeable difference in performance to completely compromised pretty much instantly. Don't try and tell me that, had it not been secured by a front rack, that the fact that it was made from steel would have helped me avoid dental work. The other fork I broke because I wasn't looking where I was going and rode into the back of a convertible at an intersection. I ended up on the trunk lid. I was going slowly, 10 mph or less, but it still wrecked the fork. Yes, it bent instead of snapping. And the good that did me was my nearly eating pavement when I remounted to go the 20 feet to get out of the intersection, because I couldn't steer the bike anymore. The point is, if you hit something hard enough to bend or break your fork, you're going down regardless AND the bike will be unridable. That's not to mention pretty good odds that you've just wrecked the frame as well, by ovalizing the headtube and/or bending or cracking the top and downtubes near the headtube.

I'll repeat myself for the final time: equivalent failure types in frames built from different materials are more-or-less equally safe or dangerous. A failure of the chainstay or seattube is benign, a failure of the fork or headtube is extremely dangerous. This is true whether it snaps or bends, whether it broke from impact or fatigue. Frame materials and the various myths surrounding their failure modes aren't particularly relevant.

That was a result of riding into a 12" high sewer drain at 30mph. I was at the race where this happened. Wheels made out of cast iron would have broken.

I was wondering if you'd chime in when I read that. That comment was a little uncool. On a side note hope the rider wasn't hurt too bad. Looks like it was a nasty crash.

Sorry but this is just a myth that is continually perpetuated by people who don't know how materials work. Aluminum is a soft, relatively pliable material. It's failure mode is often a tearing action rather than a breaking action. I've broken aluminum frames and parts in the past and not one of them has shattered like most people think they do. I've run an aluminum crowned mountain bike fork into a curb at 30+ mph and the crown bent backwards but it didn't crack or break or shatter. Most of the time when aluminum does crack, it will creak and groan and tear before it fails. My aluminum frames that broke and lots of rims that have cracked down the middle all made lots of noise before I noticed that they were cracked.

Steel parts and frames that I have broken don't crack nor bend nor make noise nor tear. They broke. No warning, no cracking, no bending. Two mountain bikes broke at the dropouts by snapping suddenly...one might say catastrophically. Pedal axles have sheared off without warning. Spokes go 'PING' and they are broken. Wheel axles have also broken suddenly on me. And it makes sense. Steel is a brittle material and stiffer than aluminum.

Thanks for the backup, cyccommute. As I said before - aluminum definitely will bend, and steel definitely will snap. I'm tired of hearing about steel failing "gracefully" and aluminum failing "catastrophically." My experience is that both can go either way. And I want to emphasize again that failure-by-bending is not a safe failure if it renders to bike uncontrollable or causes the rider lose balance and/or fall off.

yeah, not really any such thing as a safe failure mode. A slight bend is better than a shattering, but anything beyond a slight bend is going to hurt. I agree with the description above of Al failures. The main difference between steel and AL is that steel has a lot more tensile strength and Al has more of a fatigue life issue. No material is perfect. The important thing is, all material shortcomings can easily be made up for with proper design. There's a reason the tubing on AL bikes usually does not look exactly like the tubing on a steel bike, or a CF bike. Assuming you dont have a manufacturing defect or a design flaw, any frame material can be made into a bike that will last.

Well that all looks fine on the computer screen. The reality, though, remains that I've ridden away from a pair of incidents that resulted in bent steel frames, and have seen dozens of other bent steel frames and forks, but in 30 years at this game, including quite a bit of bike shop experience, I've never seen a significantly bent aluminum frame or fork. Doesn't mean it can't happen (and doesn't mean I'm attacking aluminum - anyone who thinks I am should go back and read my post that started this) but these attempts to rewrite reality are a bit surprising.

Short version: anyone interested in discovering the truth for themselves should get themselves a piece of heat-treated aluminum and a piece of 4130 steel. A few moments spent attempting to bend both will be revealing.

Indeed it will be revealing. They'll find that the aluminum bends easily in one direction but doesn't bend back all that well. And if you try to bend it back the aluminum will tear not snap. Aluminum is not a brittle material. Steel is.

And neither of those properties are a bad thing with proper design.
With "brittle" comes higher strength, which means it takes a lot more to cause a failure. Al is not as strong, but as you mention, is less brittle. All of these "strengths" and "weaknesses" of each material are easily addressed by designers and engineers. The are not generalities you can apply to say material X is good for bikes and material Y is bad.

Because I build frames, I have both those materials on hand and can promise you that is not the case. It may be with whatever alloy they're selling at Home Depot, but the heat treated 6 or 7 series aluminum that is used in bicycle tubing does not like to be bent.

But whatever. I'm done arguing about it. As I noted, I don't really have anything against aluminum in bicycles. Also as I noted, in my experience steel is slightly more reliable, but not enough to really make a difference in most cases. Why folks felt the need to jump all over that is beyond me. That's the internet, I guess.

I think most just get a bit defensive of whatever they have.
No frame is indestructible, & anything will break under certain circumstances...

It is true that aluminum is less tolerant of bending than steel...without treatment after bending. But the point is that when bent, the aluminum does not shatter like glass as so many in the anti-aluminum crowd think. Even when fractured, aluminum just doesn't propagate fractures all that fast.

The reason I jump all over this is that the anti-aluminum crowd spread myths about aluminum that just are not true. Personally, the frame material of a bike isn't something that I worry too much about in terms of strength. I've broken aluminum frames and I've broken steel frames (2 of each). I've also owned steel and aluminum frames in about equal measure. I don't look on steel frames as being indestructible nor do I look on aluminum as being fragile. Given the choice, however, I will choose aluminum over steel because of weight, especially when it comes to production bicycles. The steel ones that are offered by the major manufacturers...when you can find them...are entry level boat anchors.

I can understand using a post as a springboard to make a point. I just don't know what that point has to do with anything I posted.

That's useful to know. If I ever manufacture a frame, I might make it aluminium. There are all kinds of road, touring and mountain bike frames available but almost none for hybrids (especially compact frames with curved top tubes). I don't have the money yet to do that, but in the future...