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.
Ben