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Head Tube Failure While Riding: Consequences?

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Head Tube Failure While Riding: Consequences?

Old 08-21-15, 11:00 AM
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Head Tube Failure While Riding: Consequences?

Say a steel frame has a developed a crack in the lower head tube that extends about halfway around the lug / head tube from the rear. Obviously this lug / joint will fracture at some point, causing a break across the lower part of the head tube. I’m curious: does anyone have any knowledge or experience with what happens when a head tube fractures like this while a bike is being ridden? My guess is that it would be fairly obvious when it breaks completely through, but that the bike would remain rideable at least long enough to pull over without a serious crash.

Here’s an example image:


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Old 08-21-15, 11:10 AM
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Originally Posted by jethin
. . . when it breaks, but that the steel frame would hold the bike together . . .
You kind of have to pick one: does the headtube break OR hold together?
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Old 08-21-15, 11:15 AM
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Is your frame cracked? Do you like your teeth? How about your nose or cheek bones, those are better questions.
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Old 08-21-15, 11:17 AM
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The downtube and lower head lug are in tension. When they fail, the front end drops down and pushes the front wheel forward. What happens exactly depends on the strength and ductility of the top tube, and strength of the top/head joint.

From first hand experience, I've seen one where the top tube held and bent upward in a way that the rider could control the bike and avert a crash. Note that front wheel braking in this instance would improve the conditions.

But IMO that was a unique event, and I've seen dozens of frames where a lower joint failure led to an immediate and catastrophic upper failure, with high potential for face plant. In the cases I've seen, the extent of injury to the rider varied, and I have no direct first hand knowledge of anything causing grevious injury or death, but it remains a real possibility.

While I'd ride a bike with some lower head tube damage, such as a crash related upset at the downtube, I wouldn't ride one where I felt the risk of imminent failure was high, ie. visible cracks propagated more than 10-15% (if that). If the blue line in pure photo repreresnts the extent of an actual crack, I'd consider the frame toast (or a candidate for a retubing job)
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Old 08-21-15, 11:22 AM
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Originally Posted by AnkleWork
You kind of have to pick one: does the headtube break OR hold together?
It seems fairly obvious to me what I'm getting at, but I'm referring to the head tube cracking completely though but the bike holding "together" / rideable at least long enough to pull over and throw it in a canal.
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Old 08-21-15, 11:27 AM
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Originally Posted by Leebo
Is your frame cracked? Do you like your teeth? How about your nose or cheek bones, those are better questions.
Your questions contain implications, but convey no useful data that pertains to my question. But since you asked, no, yes, and yes.
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Old 08-21-15, 11:30 AM
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Your example appears, the 2 lugs and the head tube were made in one piece .. A mass Production expediency.

Strip it and Buy a new frame/fork-set..
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Old 08-21-15, 11:30 AM
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Originally Posted by FBinNY
The downtube and lower head lug are in tension. When they fail, the front end drops down and pushes the front wheel forward. What happens exactly depends on the strength and ductility of the top tube, and strength of the top/head joint.

From first hand experience, I've seen one where the top tube held and bent upward in a way that the rider could control the bike and avert a crash. Note that front wheel braking in this instance would improve the conditions.

But IMO that was a unique event, and I've seen dozens of frames where a lower joint failure led to an immediate and catastrophic upper failure, with high potential for face plant. In the cases I've seen, the extent of injury to the rider varied, and I have no direct first hand knowledge of anything causing grevious injury or death, but it remains a real possibility.

While I'd ride a bike with some lower head tube damage, such as a crash related upset at the downtube, I wouldn't ride one where I felt the risk of imminent failure was high, ie. visible cracks propagated more than 10-15% (if that). If the blue line in pure photo repreresnts the extent of an actual crack, I'd consider the frame toast (or a candidate for a retubing job)
This is interesting information that pertains directly to my question -- a typically informed and useful FBinNY post. Thank you.
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Old 08-21-15, 11:33 AM
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Oh, you've drawn the Crack with a magic marker!
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Old 08-21-15, 11:42 AM
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Originally Posted by jethin
Your questions contain implications, but convey no useful data that pertains to my question. But since you asked, no, yes, and yes.
The answer was no more silly than the question. Opinions about what might happen are worthless for two reasons:

1. The possibility of what might happen is much less important than what will happen.

2. Nobody can predict what will happen in your case.

When you put 1 and 2 together the conclusion is: Don't ride the bike.
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Old 08-21-15, 11:59 AM
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Originally Posted by jethin
It seems fairly obvious to me what I'm getting at, but I'm referring to the head tube cracking completely though but the bike holding "together" / rideable at least long enough to pull over and throw it in a canal.
I'm just curious how many angels can dance in your hypothetical crack.
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Old 08-21-15, 12:03 PM
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Maybe I can help you out by dissipating your confusion a little. The headtube is part of the frame. If the headtube breaks, then the frame is broken. "Broken" means it no longer holds together. Perhaps the steerer would hold the headtube together a for while, but I don't think you asked that.
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Old 08-21-15, 12:04 PM
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I agree @cny-bikeman, but that's why I asked for knowledge or experience of such failures instead of opinions. I think we all know what opinions are like.
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Old 08-21-15, 12:08 PM
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Originally Posted by jethin
I agree @cny-bikeman, but that's why I asked for knowledge or experience of such failures instead of opinions. I think we all know what opinions are like.
Just curious, do you actually ride?
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Old 08-21-15, 12:27 PM
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Originally Posted by FBinNY
The downtube and lower head lug are in tension. When they fail, the front end drops down and pushes the front wheel forward. What happens exactly depends on the strength and ductility of the top tube, and strength of the top/head joint.

From first hand experience, I've seen one where the top tube held and bent upward in a way that the rider could control the bike and avert a crash. Note that front wheel braking in this instance would improve the conditions.
I had an old Murray Eliminator that had that happen while my brother was riding it. The front end lowered and the front wheel went forward, and he skidded to a stop when the pedals started hitting the ground. Didn't crash, thankfully.

My dad had a friend of his with a welder bend the headtube back into position and re-weld the bottom tube in place. It held for the remainder of the bike's life when a few years later one side of the handlebar snapped off. That one didn't end as pretty.
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Old 08-21-15, 12:29 PM
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Two interesting points to consider:

1. If the frame was properly mitered when built and the crack is only on the lug it may not matter since the real strength of a lugged joint is at the tube juncture.

2. The head tube is in compression via the steering tube and HS assembly, so even if it cracks as long as it is still attached to the top and down tubes it should not separate.


All that being said, IMHO only a fool would ride that frame...
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Old 08-21-15, 01:08 PM
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Originally Posted by rmfnla
2. The head tube is in compression via the steering tube and HS assembly, so even if it cracks as long as it is still attached to the top and down tubes it should not separate.

All that being said, IMHO only a fool would ride that frame...
This is along my line of thinking. Common wisdom -- which is often sound -- holds that cracks in head tube lugs are dangerous. But I'm curious about the mechanics and real world examples of such failures and their effects. The example image I posted is based on the largest head tube crack I've seen.
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Old 08-21-15, 01:12 PM
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FWIW, many lugs are cast so they would be susceptible to cracking well before a frame tube, but I still wouldn't ride it...
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Old 08-21-15, 01:39 PM
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I thought I saw a bike, perhaps in the Wacky thread recently with that problem, but can't find it.

But, the breaks do occur occasionally
https://www.bikeforums.net/classic-vi...rek-830-a.html
https://www.bikeforums.net/classic-vi...fty-bucks.html
https://www.bikeforums.net/classic-vi...th-fixing.html

A non-displaced crack would be much easier to repair than a complete fracture.

Depending on the bike, I'd try welding and riding. Or, perhaps replacing the head tube.

Apparently many of the older metals are less resilient to TIG welding heat, and there is risk of weld contamination with a brazed joint. Nonetheless, TIG welding would be quick and easy to do on a beater bike.
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Old 08-21-15, 01:50 PM
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Originally Posted by jethin
It seems fairly obvious to me what I'm getting at, but I'm referring to the head tube cracking completely though but the bike holding "together" / rideable at least long enough to pull over and throw it in a canal.
The real question is: will this break when you are just riding along or when you've hopped a pothole (or hit that pothole? Will you be riding at 18 mph or downhill at 35? These could be major factors in how controllable the bike will be.

Steel is very forgiving and gives you second chances. This frame has indicated quite visibly that it is toast and hasn't screwed you over yet. It might be time to take a hint, especially given what part of the bike is likely to be compromised if that crack progresses. If it were a seat tube or chainstay, I would say to ride it until it breaks. But not a head tube that looks like that. Too much to lose.

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Old 08-21-15, 07:10 PM
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Well, first, if there is a crack, that's likely due to fatigue failure. And a crack is a stress concentrator. So the material failed in normal use due to repetitive stress, and you've got a situation that will increase the magnitude of that stress in an already-weakened area. See where this is heading? As some have noted, a failure might be "soft", in which the top tube holds things together long enough for you to slow down. As someone who has gone over the bars due to a bike failure, breaking my jaw and cracking 13 teeth, I'd not bet on a soft failure.

A framebuilder figured out a way to get that lug on there. You may seek out someone who could get it off and replace it. Depending on your bikes coolness and expense factor, it may be worth it. But betting on the thing holding together? Not the best option. Or, you could try it and reflect on the wisdom of trying it as they scrape the road dirt out of the chin part of your jawbone.
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Old 08-21-15, 07:20 PM
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All this said, what are the non-visual warning signs of a cracking head tube? My whole 20-year-old frame is covered with tourist decals and my eyes have gotten pretty sucky in the past few years. Is there anything I might feel or hear that should give me a heads-up?
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Old 08-21-15, 08:47 PM
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Originally Posted by Papa Tom
All this said, what are the non-visual warning signs of a cracking head tube? My whole 20-year-old frame is covered with tourist decals and my eyes have gotten pretty sucky in the past few years. Is there anything I might feel or hear that should give me a heads-up?
Fill the frame with colored smoke and look for the jetting points Actually I have heard of pressure holding as a test for cracks. Things like industrial tanks and propellers. Andy.
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Old 08-21-15, 09:01 PM
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Originally Posted by Papa Tom
All this said, what are the non-visual warning signs of a cracking head tube? My whole 20-year-old frame is covered with tourist decals and my eyes have gotten pretty sucky in the past few years. Is there anything I might feel or hear that should give me a heads-up?
The gold standard for crack detection in steel is magnaflux.

However, unless you have a specific reason to be worried you might do what millions and millions of cyclists have done for years and trust your steel frame until it gives you a reason not to.
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Old 08-21-15, 09:19 PM
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