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Shock Pump Newbie Question



 
 
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  #1  
Old August 20th 04, 12:34 PM
Tony Scilipoti
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Default Shock Pump Newbie Question

I've just gone from a hardtail with a coil fork to a new FS with air
shocks on both ends, and I must be missing something because I can't
get air into the shocks. I have a brand new SKS shock pump with a
screw-on fitting for the Schrader valves on the shocks. I pump up the
shock to the desired pressure (or a bit over). Then when I go to
unscrew the pump fitting, most - not just some, but most - of the
pressure escapes from the shock while I'm unscrewing it. Like, for
example, it will go down from 8 bar to 2 bar. In the case of the small
SPV chamber on my Swinger rear shock, it ALL escapes. (I press on the
pin in the center of the valve and no hiss.) Reminds me of the useless
tire pumps of my childhood.

I have read some other posts on this and everyone says "Oh, you're
just hearing the leftover air in the pump hose escaping." No. When I
check the pressure using a tire gauge, or by observing sag, I can see
that there's hardly any air in the shock. So I have two questions:

1) With a screw-on fitting like this, why WOULDN'T you expect all the
air to escape as you're unscrewing it, given that there is a
significant period of time during which the valve is still depressed
(allowing air out of the shock) but the fitting is already loose
enough to let air escape around the threads of the valve stem? Isn't
this precisely why all tire pumps now have the flip-a-lever style of
seal?

2) Is there some special technique that I'm supposed to use to keep
this from happening? What am I missing? What's the secret formula?

Thanks!
- Tony
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  #2  
Old August 20th 04, 01:58 PM
Michael Dart
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Default


"Tony Scilipoti" wrote in message
om...
I've just gone from a hardtail with a coil fork to a new FS with air
shocks on both ends, and I must be missing something because I can't
get air into the shocks. I have a brand new SKS shock pump with a
screw-on fitting for the Schrader valves on the shocks. I pump up the
shock to the desired pressure (or a bit over). Then when I go to
unscrew the pump fitting, most - not just some, but most - of the
pressure escapes from the shock while I'm unscrewing it. Like, for
example, it will go down from 8 bar to 2 bar. In the case of the small
SPV chamber on my Swinger rear shock, it ALL escapes. (I press on the
pin in the center of the valve and no hiss.) Reminds me of the useless
tire pumps of my childhood.

I have read some other posts on this and everyone says "Oh, you're
just hearing the leftover air in the pump hose escaping." No. When I
check the pressure using a tire gauge, or by observing sag, I can see
that there's hardly any air in the shock. So I have two questions:

1) With a screw-on fitting like this, why WOULDN'T you expect all the
air to escape as you're unscrewing it, given that there is a
significant period of time during which the valve is still depressed
(allowing air out of the shock) but the fitting is already loose
enough to let air escape around the threads of the valve stem? Isn't
this precisely why all tire pumps now have the flip-a-lever style of
seal?

2) Is there some special technique that I'm supposed to use to keep
this from happening? What am I missing? What's the secret formula?

Thanks!
- Tony


The fitting on a shock pump is designed to close the schrader valve before
the o-ring breaks it's seal. And true the hissing you hear should only be
the air escaping from the pump. If this isn't happening either the valve
core in the schrader isn't screwed in all the way or the o-ring seal is bad
in the pump. Also on some pumps the part that presses down on the valve is
adjustable with a small flat bladed screwdriver. You're right that your are
dealing with such a small volume of air it doesn't take much of a leak to
let it all out. Take the bike to your LBS and see if they'll let you try
another pump.

A tip if you get this working only thread the pump on until the gauge
registers pressure. This prevents the o-ring in the pump from getting
damaged. Also if you are using the pump for your fork with a adapter, don't
leave the adapter in the pump. This will leave the o-ring compressed.

Mike


  #3  
Old August 21st 04, 06:37 AM
ZeeExSixAre
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Default

example, it will go down from 8 bar to 2 bar. In the case of the small
SPV chamber on my Swinger rear shock, it ALL escapes. (I press on the
pin in the center of the valve and no hiss.) Reminds me of the useless


My shock pump for my Swinger 4-way rear rear always had that problem.

2) Is there some special technique that I'm supposed to use to keep
this from happening? What am I missing? What's the secret formula?


Different shock pump. We have several at the shop so it didn't matter.

--
Phil, Squid-in-Training



  #4  
Old August 21st 04, 10:41 PM
Tony Scilipoti
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Default

"ZeeExSixAre" wrote in message . ..
example, it will go down from 8 bar to 2 bar. In the case of the small
SPV chamber on my Swinger rear shock, it ALL escapes. (I press on the
pin in the center of the valve and no hiss.) Reminds me of the useless


My shock pump for my Swinger 4-way rear rear always had that problem.

2) Is there some special technique that I'm supposed to use to keep
this from happening? What am I missing? What's the secret formula?


Different shock pump. We have several at the shop so it didn't matter.


Can you (or anyone) make a specific pump recommendation? Thanks. - Tony
  #5  
Old August 23rd 04, 07:47 AM
ZeeExSixAre
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Posts: n/a
Default

Tony Scilipoti wrote:
"ZeeExSixAre" wrote in message
. ..
example, it will go down from 8 bar to 2 bar. In the case of the
small SPV chamber on my Swinger rear shock, it ALL escapes. (I
press on the pin in the center of the valve and no hiss.) Reminds
me of the useless


My shock pump for my Swinger 4-way rear rear always had that problem.

2) Is there some special technique that I'm supposed to use to keep
this from happening? What am I missing? What's the secret formula?


Different shock pump. We have several at the shop so it didn't
matter.


Can you (or anyone) make a specific pump recommendation? Thanks. -
Tony


The one that screwed up was called the "Pollinator" or something along those
lines. The one that worked was a generic silver one with no brand name. It
is likely you can grind down the post in the center of the screw-on part so
that it doesn't press the valve in when it becomes unsealed. It certainly
wouldn't hurt, as it seems that you've got the product and all you need is a
little modification. Plus, you have nothing to lose, since you're just
going to continue to lose air if you don't do anything

--
Phil, Squid-in-Training



 




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