silca super pista: should wheel pressure show?

[Gbgbgbgb]

Hi,

I just got a (sort of) new silca super pista pump. It came without a manual - but Silca, Italy have
graciously offered to send me one. (I have another thread here with that ordeal)

My question, while I wait for the manual - after some tweaking with the presta valve I manage to
pump it up.

However, neither the white nor red niddle at any point show me the air pressure of the wheel
i'm pumping.

I set the red needle to, say 45 PSI, and start pumping. The white needle just jumps up and settles
back to zero every stroke. I pump until it "seems" right.

Is this how things should be or did I get a defective pump ?!

Thank you! -Gill

 

[Harris]

gbgbgbgb <[email protected]> wrote:

> I just got a (sort of) new silca super pista pump. It came without a manual - but Silca, Italy
> have graciously offered to send me one. (I have another thread here with that ordeal)

> My question, while I wait for the manual - after some tweaking with the presta valve I manage to
> pump it up.

> However, neither the white nor red niddle at any point show me the air pressure of the wheel i'm
> pumping.

> I set the red needle to, say 45 PSI, and start pumping. The white needle just jumps up and settles
> back to zero every stroke. I pump until it "seems" right.

> Is this how things should be or did I get a defective pump ?!

The red needle is just a visual aid; you set that to the desired pressure, and then pump until the
white needle is coincides with the red.

If the tire is inflating, but the white needle stays at zero, you may have a bad check valve.

Art Harris

 

[Michael]

[email protected] wrote...
> I just got a (sort of) new silca super pista pump. It came without a manual - but Silca, Italy
> have graciously offered to send me one. (I have another thread here with that ordeal)

How did you contact them? I couldn't find them anywhere on the web, and my pump didn't come
with a manual.

<snip>
> neither the white nor red niddle at any point show me the air pressure of the wheel i'm pumping.

I had the same problem after I disassembled my pump to lubricate everything (although in my case the
white needle would rise with the pump, but not hold the pressure in the gauge). In my case the
grease I used in the pump shaft got pushed into the check valve, causing it to be stuck open.

Take apart the check valve (it's in the module that contains the gauge) - it's just a disk on a
stick with a spring. Clean the parts, lubricate it lightly with oil, and put it back together.
Should solve your problem.

Michael

 

[Gbgbgbgb]

> > That is true, but unless your pump is leaking, the needle should hold at the last pressure
> > reached (or close to it, anyway) because of air trapped in the hose between the tire valve and
> > the check valve in the pump cylinder. That's what mine does; the pressure indicating needle
> > gradually drops if I stop pumping, but it's slow enough that I don't have a problem seeing the
> > reading. The peak of the needle's movement is approximately your tire pressure. If it drops off
> > quickly, you probably have a leaking check valve or a leaking connection.
>
> The pump is leaking somehow. Usually it's just around the valve stem. Switching to tubes with
> smooth (non-threaded) valve stems might help, or you might need a new pump head or O-ring. As
> David says, just look at the highest reading before the leakdown starts. The tube itself isn't
> leaking, because of the one-way Presta valve -- just the air in the pump and hose.
>
> Matt O.

Thanks for both clarifications. Seems to me that my pump is leaking because the needle does drop
very rapidly. It also seems that I can tip it to any "height" I want by just stroking harder, so I
guess you both mean read the needle as you apply measured pumping strokes.

Now, I am left wnodering whether the rapid drop is not to blame on my ignorance. I have just
recently figured out how to handle the presta valve itself - ie, to loosen it so it releases air
upon slight tapping on head before inserting into pump head. Now I'm thinking maybe im not placing
the pump head properly on the valve. I do seem to struggle a lot with the pump head before it is
resting in a position that is both not leaking air from the wheel and allowing for pumping. I'll
have another look in the morning.

 

[Matt O'Toole]

"gbgbgbgb" <[email protected]> wrote in message
news:[email protected]...

> Thanks for both clarifications. Seems to me that my pump is leaking because the needle does drop
> very rapidly. It also seems that I can tip it to any "height" I want by just stroking harder, so I
> guess you both mean read the needle as you apply measured pumping strokes.

Yes, as you come to the end of the stroke, the reading will peak, and then fall as the air leaks out
of the pump.

> Now, I am left wnodering whether the rapid drop is not to blame on my ignorance. I have just
> recently figured out how to handle the presta valve itself - ie, to loosen it so it releases air
> upon slight tapping on head before inserting into pump head.

Yes, they tend to stick unless you loosen them this way first. I don't know why.

If everything's working properly, you can feel the pressure build inside the pump, and then lessen
as the valve opens and the air rushes into the tube.

> Now I'm thinking maybe im not placing the pump head properly on the valve. I do seem to struggle a
> lot with the pump head before it is resting in a position that is both not leaking air from the
> wheel and allowing for pumping.

Smooth (non-threaded) valve stems help here. Look for Continental and Michelin tubes, which have
smooth stems.

Matt O.

 

[Gbgbgbgb]

> > Now I'm thinking maybe im not placing the pump head properly on the valve. I do seem to struggle
> > a lot with the pump head before it is resting in a position that is both not leaking air from
> > the wheel and allowing for pumping.
>

Hey, today I managed to battle the pump head into place - on both wheels. And then I finally got the
desired behaviour you were describing - needle was practically standing in place at given pressure.
I guess I learned how to place the head thing, although I am not quite sure what the trick was.
Either way - lots of thanks you guys!!!

> Smooth (non-threaded) valve stems help here. Look for Continental and Michelin tubes, which have
> smooth stems.
>

I suppose you mean after I've done this tube in? I'll remember to enquire about that next visit
to my LBS.

Thanks again! -Gill

 

[Hugh Fenton]

"gbgbgbgb" <[email protected]> wrote in message
news:[email protected]...
> > > Now I'm thinking maybe im not placing the pump head properly on the valve. I do seem to
> > > struggle a lot with the pump head before it is resting in a position that is both not leaking
> > > air from the wheel and allowing for pumping.
> >
>
> Hey, today I managed to battle the pump head into place - on both wheels. And then I finally got
> the desired behaviour you were describing - needle
was
> practically standing in place at given pressure. I guess I learned how to place the head thing,
> although I am not quite sure what the trick was. Either way - lots of thanks you guys!!!
>
> > Smooth (non-threaded) valve stems help here. Look for Continental and
Michelin
> > tubes, which have smooth stems.
> >
>
> I suppose you mean after I've done this tube in? I'll remember to enquire about that next visit
> to my LBS.
>
> Thanks again! -Gill

This of course raises the question of what is wrong with Schrader type valves. Looking at the
construction I guess they would easily handle 120psi - and are used on heavy trucks at high
pressures.

I've always been a presta user myself - but except for weight and status - why? Hugh Fenton

 

[David Kerber]

In article <[email protected]>, [email protected] says...
>
> "gbgbgbgb" <[email protected]> wrote in message
> news:[email protected]...
> > > > Now I'm thinking maybe im not placing the pump head properly on the valve. I do seem to
> > > > struggle a lot with the pump head before it is resting in a position that is both not
> > > > leaking air from the wheel and allowing for pumping.
> > >
> >
> > Hey, today I managed to battle the pump head into place - on both wheels. And then I finally got
> > the desired behaviour you were describing - needle
> was
> > practically standing in place at given pressure. I guess I learned how to place the head thing,
> > although I am not quite sure what the trick was. Either way - lots of thanks you guys!!!
> >
> > > Smooth (non-threaded) valve stems help here. Look for Continental and
> Michelin
> > > tubes, which have smooth stems.
> > >
> >
> > I suppose you mean after I've done this tube in? I'll remember to enquire about that next visit
> > to my LBS.
> >
> > Thanks again! -Gill
>
> This of course raises the question of what is wrong with Schrader type valves. Looking at the
> construction I guess they would easily handle 120psi - and are used on heavy trucks at high
> pressures.

Nothing wrong with Schrader's. I use them with 120psi tires on my old bike, which has
Shrader-drilled rims, and they work fine. Those tubes don't seem to hold pressure quite as well as
the presta tubes on my other bike, but I don't know if that's a function of the tube or the valve.

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