1" threaded steertube snaps in two

kwalters said:

Fortunately, I was moving slowly, and no face plant ensued.
The front wheel went to the left, the bars went to the right,
and I just sort of stumbled forward to a surprised toptube-
into-crotch stop.

FWIW:
The bike is an old 22" Univega Alpina Pro XT 6-speed used as a
commuter, original owner, purchased maybe 20 years ago. No use
more rugged than commuting and an occasional county gravel road.

Original chrome plated fork with "Cro-mo" stamped on the steertube.
Steertube is ~185mm long with ~110mm of thread. Failure
occured at the very base of the threads. Fairly clean break.

My weekend plans are to remove and check the 1" threaded forks
on the three other 1" threaded-fork bikes in the garage.

Was the stem pulled up high enough that the expander plug acted on the
threads? --D-y

On Fri, 04 Aug 2006 12:35:10 -0600, kwalters <[email hidden]>

Quoted message said:

Fortunately, I was moving slowly, and no face plant ensued.
The front wheel went to the left, the bars went to the right,
and I just sort of stumbled forward to a surprised toptube-
into-crotch stop.

FWIW:
The bike is an old 22" Univega Alpina Pro XT 6-speed used as a
commuter, original owner, purchased maybe 20 years ago. No use
more rugged than commuting and an occasional county gravel road.

Original chrome plated fork with "Cro-mo" stamped on the steertube.
Steertube is ~185mm long with ~110mm of thread. Failure
occured at the very base of the threads. Fairly clean break.

110mm of thread on a 185mm steer tube? That sounds like the wedge was
just about guaranteed to be above the end of the threads, which is not
a good thing. The threads should ideally end above the wedge so that
the most likely failure mode becomes one where the upper bearing flops
around but the fork and bars remain connected.

Quoted message said:

My weekend plans are to remove and check the 1" threaded forks
on the three other 1" threaded-fork bikes in the garage.

I think you're going to find that the threads on the rest are shorter.

--
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