Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
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Looking at the photo, it appears to be a "cold joint". By that I mean that the crown and base of the steerer weren't complete heated to the proper temperature for the braze to flow in and fill the joint. If this were a sweat soldered copper plumbing joint it would have leaked, but it's hard to spot this in brazed bike joints until they fail.
Cold joints are more common than most would like to believe, but are proof of the amount of margin of error in classic brazed construction, in that most hold up way longer that you'd expect.
When I first started in the bike biz many decades ago, we had a run of track forks with this problem. Since there's no brake bolt to provide a safety net, we went to great lengths to track down and replace all of them (this was before product recalls were common). After that we insisted that the builder drive a pin into all our track forks prior to brazing.
IMO it would be more expensive to repair than to replace with a new fork, especially because the crown flexed open making for a poor fit.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
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