motorapido

See pics and diagnose the cause of the damage to this fork steerer. Despite the scoring looking quite deep in the pictures, upon measuring the scoring, I confirmed that they are no deeper than the milled slot in the fork steererr that the slotted washer mates with. I am guessing this was caused by a loose headset, which must have caused the steerer to come into contact with a stationary part of the headset -- probably the headtube top race. Fortunately, I found this in the process of taking this fork out of service, to replace it with a NOS fork and a new cartridge headset. I would think that if this fork were used for a long time in this current condition that the steerer would eventually crack off at this scored section, right?

Interestingly, the scoring is on the front-facing section of the steerer. I would have thought that a loose headset causing the steerer to rub would cause it to rub on the back side. Is my logic accurate or inaccurate?

FBinNY 

Yes, the likely cause is a loose headset, but could also be some kind of debris, or a misloaded ball when you assembled the headset.

The shape and location of the gouge has me thinking if maybe it's below the headset altogether. Maybe the rivet or screw holding on a head badge.

However, you're right that if it were rubbing against the lip of the headset, the worst damage would be toward the back. I'd start the diagnosis by installing the upper race and locknut to gauge the height vs. the headset, then looking for corresponding damage in the headset or head tube .

Wilfred Laurier

the super smooth round profile
makes me think misplaced headset ball
but i could be wrong

RavingManiac

Wouldn't that steerer be a stronger steel than anything it would likely come in contact with? That's a serious gouge, almost looks intentional, like someone was going to cut down the steerer and found out their old rusty hacksaw blade was no match for the chromo steerer.

motorapido

Ah ha. I like your reasoning, and I bet it came from a ball becoming trapped where it should not have been. I will pull the fork and inspect the head tube to look for a head badge rivet as a possible cause, too. Man, to think of a steerer shearing off -- what a terrifying thought. Yeeeeeeeeeeeeeoooooooooooch!

RavingManiac

That looks like a possibility. Couldn't have been buttery smooth steerer action.

motorapido

I would think that a hardened ball bearing would be far, far harder than cromo steel, and the profile of the score pretty much matches the profile a a loose ball bearing.

RavingManiac

That blue looks familiar, is that fork off a Raleigh Chill mountain bike, a Tange Bigfork by any chance?

motorapido

Tange fork on the Panasonic-made frame of a 1976 Schwinn Super Le Tour 12.2. My darling baby, which I bought brand-new with my paper route money. Many tens upon tens of thousands of miles on the old girl. I bought a NOS Tange fork with the standard stem diameter so I can get away from the dumb Schwinn-specific stem diameter. Glad I did, now that I discovered this damage.

FBinNY 

Not to worry, that simply wouldn't have happened. the quill stem extends well below the affected area, so if/when the top failed, the top bearing would become very obviously loose, but the fork, steerer, stem has no place to go and would allow you to maintain control and even ride the bike home (as long as you take it easy and don't have far to go)

Love or hate various bike designs, but most of the older systems evolved when materials and processes were less reliable and so had a certain amount of redundancy and safety built in. I think back to vintage fork steerers that had a safety device in the form of a wooden dowel plug extending from the fork crown to well in to the lower bearing. Steerer snaps, and the plug prevents a face plant.

Wilfred Laurier

cromo steel has very good mechanical properties
but is not exceptionally hard or immune to scratching or grinding

fietsbob

At least you caught it before it broke off .

replacing it .. Good plan ...

leob1

It happened to me. Luckly I knew something was wrong, so I was almost stopped when it broke. I landed in front of an ice cream place, on my face. All those folks wating to get ice cream cones saw me leave half my face in the street. It hurt.

Grand Bois

It must have sheared of at the bottom.