Dicky prestas

DeF said:

The odd thing is that often, the valves on my steel roadie act as if I
haven't unseated them. The pressure in the pump reaches 200psi then,
bang, the valve releases the pressure into the tire and I can pump up as
normal. This doesn't happen with my "good" bike.

This happens on some of our bikes occasionally, but I don't
remember if the pressure ever goes that high before it cracks.

I always figured it was due to moisture or something.
*shrug*

-kt

--
Kingsley Turner,
(mailto: [email hidden])
http://MadDogsBreakfast.com/ABFAQ - news:aus.bicycle Frequenly Asked Questions

DeF said:

The odd thing is that often, the valves on my steel
roadie act as if I haven't unseated them. The pressure
in the pump reaches 200psi then, bang, the valve
releases the pressure into the tire and I can pump up
as normal. This doesn't happen with my "good" bike.

I have a similar problem with some of my Presta's. I find I have to get
the lock nut in the right position on the screw before I can get any air
into the tube. Sometimes it's too high, sometimes it's too low. Not
sure if this is for the same reason you've had your experiences but I
just assumed it was something to do with the relative position of the
pump components and whether or not the valve has been released. Too
high and the pump head won't engage properly, too low and the valve
won't release. Perhaps you're avoiding these potential problems by
applying enough pressure to shift the valve??

Quoted message said:

Something to do with age of tubes/valves? They're
pretty old as I've not punctured for ages (damn it,
I've mentioned the p-word and will no doubt get one
next time I'm out).

No need to worry here. My last two rides home have given the puncture
gods enough to keep them satisfied for a while.

--
Bean

Remove "yourfinger" before replying

DeF said:

As I'm sure most of us do, I pump up my tires
before I head out, if only to use the gauge on
my floor pump to check the pressure.

Procedure is to first loosen lock nut, tap valve
to unseat it then attach pump head and start pumping.

The odd thing is that often, the valves on my steel
roadie act as if I haven't unseated them. The pressure
in the pump reaches 200psi then, bang, the valve
releases the pressure into the tire and I can pump up
as normal. This doesn't happen with my "good" bike.

Something to do with age of tubes/valves? They're
pretty old as I've not punctured for ages (damn it,
I've mentioned the p-word and will no doubt get one
next time I'm out).

You may find that the valve pin is bent - it happens over time. Don't
worry about it...

happens to me too.
I thought it was a 'feature'. 😕

Bleve said:

DeF said:

As I'm sure most of us do, I pump up my tires
before I head out, if only to use the gauge on
my floor pump to check the pressure.

Procedure is to first loosen lock nut, tap valve
to unseat it then attach pump head and start pumping.

The odd thing is that often, the valves on my steel
roadie act as if I haven't unseated them. The pressure
in the pump reaches 200psi then, bang, the valve
releases the pressure into the tire and I can pump up
as normal. This doesn't happen with my "good" bike.

Something to do with age of tubes/valves? They're
pretty old as I've not punctured for ages (damn it,
I've mentioned the p-word and will no doubt get one
next time I'm out).

You may find that the valve pin is bent - it happens over time. Don't
worry about it...

As per usual for USENET, I posted before doing
a more thorough examination. Now that that has
been done, there is another feature of the valves.
The locknut does not screw down tight onto the body
of the valve. I can see that when it is tightened,
there is more thread above the locknut than on my
new tubes. Thus, I think that the rubber seating
(assuming there is such a thing) inside the valve has
worn out. I might even speculate that whereas it was
originally a flattish cone, it is now a more tapered
cone that more easily jams.

So, solution is to replace the tubes with new ones.
Also, I may have been over tightening the locknuts
thus contributing to the shortening of the valve life.
When I've pulled the old tubes off, I'll pull apart
the valves to test the above hypothesis.

LAL. (*)

DeF.

(*) Live and Learn

--
e-mail: d.farrow@your finger.murdoch.edu.au
To reply, you'll have to remove your finger.

DeF said:

So, solution is to replace the tubes with new ones.

That would be a bit rash for me. I usually keep tubes until there's
more patch than not, and they fail completely one way or another!

Donga