presta valve rocket

may have said:

My father arrived back at the train station today to find that the
front tyre was completely flat and had a pleasant walk home in the
rain. I've just taken the tyre off and the Presta valve is sheered off
about 3mm from the base. The metal tubing is actually fractured. Would
this be something that happens occasionally with these valves.

I assume that the broken-off piece is still present. If it isn't,
then you should immediately suspect vandalism. IMLE, Presta stem
failure is usually found on bikes whose tubes are pumped up using an
old-style hoseless pump. The stem breaks off just above the securing
nut after having been bent back and forth by the surplus motion of the
pump body...but it remains in place, as it must unless the core breaks
as well.

Quoted message said:

Has anyone else had it happen.

If you mean Presta stem fracture, yes, for the reason cited, but only
once as a delayed event.

Quoted message said:

I thought that the 60 psi pressure might be
too much for the tube.

Not bloody likely. I've got well over 100psi in some of mine. That
stem would be proof to a much higher pressure than the tire, and the
tube will withstand whatever the tire can hold.

Quoted message said:

Seems pretty hairy though, if it had shot off
during riding it could of had someone's eye out.

The risk from stem failure is miniscule, nearly zero in fact with the
Presta where the fractured stem will remain in place due to the core
not being able to blow out. If the core failed as well, the velocity
of ejection would not be great, though.

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Werehatrack said:

I assume that the broken-off piece is still present.  If it isn't,
then you should immediately suspect vandalism.

As i understand it, the bike was locked in one of those bike kennels,
which have fortunately been installed at some UK train stations in
order to stop the little rascals supplementing their welfare payments.
I installed a spare wheel last night which did the trick for today. He
came back tonight with the said Presta valve in hand, so obviously it
had gone bang inside the kennel during the day. I think, looking at
the old tube, it might be the original Raleigh rube, so it probably
has had it's fair share of hoseless pumps during its faithful
lifetime. I tried to get a Presta valved tube today and two shops said
that they no longer carry them because they just don't get asked for
them. That seems a bit funny to me, i thought the Presta was the
modern valve. The rim is drilled for a Presta only, but the bike shop
advised drilling it, but my drills are allergic to stainless steel.
I've found another Presta at my local Halfords, so it's all fixed and
the the Atom Maillard hub spins for 9 minutes, so the tube and tyre
are well balanced. Thanks for the reply.
all the best, Nick. �