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understanding the RockShox suspension pump and valve



 
 
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  #1  
Old November 6th 18, 08:45 PM posted to rec.bicycles.tech
Emanuel Berg[_3_]
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Posts: 31
Default understanding the RockShox suspension pump and valve

When I first got the pump, I filled the chamber
to exactly 120psi. The release button and the
gauge on the RockShox suspension pump makes
this easy to do to a high degree of precision.

The other day I thought I'd try it again and
I noticed it took four strokes to get it up to
120psi again!

Is this some property of the gauge?

How much psi enters the chamber for
every stroke?

Or did the seemingly (?) missing amount leave
the chamber when connecting the pump to
the valve?

Or is there a small-but-steady leak from the
chamber from normal usage?

--
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  #2  
Old November 15th 18, 10:11 PM posted to rec.bicycles.tech
Gregory Sutter
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Posts: 164
Default understanding the RockShox suspension pump and valve

On 2018-11-06, Emanuel Berg wrote:
When I first got the pump, I filled the chamber
to exactly 120psi. The release button and the
gauge on the RockShox suspension pump makes
this easy to do to a high degree of precision.

The other day I thought I'd try it again and
I noticed it took four strokes to get it up to
120psi again!

Is this some property of the gauge?


I have the same pump. It's a common one, resold under many
brand names, probably because it's inexpensive and works well.

Possibilities:

- loss of a small amount of air when disconnecting pump
- shock--pump pressure equalization when connecting pump
- slow leak from shock
- gauge hysteresis or inaccuracy

At a guess, I'd rate them in that order of likelihood.

--
Gregory S. Sutter Mostly Harmless

http://zer0.org/~gsutter/
  #3  
Old November 16th 18, 12:45 AM posted to rec.bicycles.tech
[email protected]
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Posts: 16
Default understanding the RockShox suspension pump and valve

Thanks!
  #4  
Old November 26th 18, 10:41 PM posted to rec.bicycles.tech
Emanuel Berg[_3_]
external usenet poster
 
Posts: 31
Default understanding the RockShox suspension pump and valve

Gregory Sutter wrote:

I have the same pump. It's a common one,
resold under many brand names, probably
because it's inexpensive and works well.

Possibilities:

- loss of a small amount of air when disconnecting pump
- shock--pump pressure equalization when connecting pump
- slow leak from shock
- gauge hysteresis or inaccuracy

At a guess, I'd rate them in that order
of likelihood.


I think you are right because "slow leak from
shock", wouldn't that mean the chamber would be
*empty* pretty soon?

So if we believe in your reasons 1 and 2, what
is the implication of that? Say you want
120psi, maybe you should put in 120psi and then
some - 125psi?

--
underground experts united
http://user.it.uu.se/~embe8573
  #5  
Old November 26th 18, 11:05 PM posted to rec.bicycles.tech
Sir Ridesalot
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Posts: 3,819
Default understanding the RockShox suspension pump and valve

On Monday, November 26, 2018 at 4:41:42 PM UTC-5, Emanuel Berg wrote:
Gregory Sutter wrote:

I have the same pump. It's a common one,
resold under many brand names, probably
because it's inexpensive and works well.

Possibilities:

- loss of a small amount of air when disconnecting pump
- shock--pump pressure equalization when connecting pump
- slow leak from shock
- gauge hysteresis or inaccuracy

At a guess, I'd rate them in that order
of likelihood.


I think you are right because "slow leak from
shock", wouldn't that mean the chamber would be
*empty* pretty soon?

So if we believe in your reasons 1 and 2, what
is the implication of that? Say you want
120psi, maybe you should put in 120psi and then
some - 125psi?

--
underground experts united
http://user.it.uu.se/~embe8573


Sometimes a slow leak in a bicycle tire will only drop pressure to a certain point wherein the pressure is now low enough that the slow leak stops until the pressure is topped up by the user again. Perhaps the same thing is happening with your shocks?

Cheers
 




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