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SCHOCKPUMPS!

MikeD

MikeD

Leader and Demogogue of the Ridemonkey Satinists
Oct 26, 2001
11,690
1,735
chez moi
So I keep reading people YELLING IN ALL CAPS ONLINE that no shrader valve shock pumps lose air when removing them.

This is odd, because if I unscrew the plain old shrader-thread head from my shock/fork using my Fox shock pump, the shock will fully deflate. So there's a demonstrable point of being partially engaged and losing pressure as I unthread it, fast as I might try to unthread quickly to avoid it.

I looked at a few fancy and not-fancy adapters supposed to cure this, but not sure more potential points of failure make sense. Plus there are new Topeak and other pumps with such features built in, and digital readouts that kinda make sense given the necessary precision with all this.

What do you guys use/think?
 
Nick

Nick

My name is Nick
Sep 21, 2001
24,064
14,711
where the trails are
I have an older DT Swiss zero-loss shock pump that is awesome. If they were still available I'd buy a spare. See if you can find one of these?
 
Jm_

Jm_

sled dog's bollocks
Jan 14, 2002
18,995
9,655
AK
There is a spring loaded valve in the shock, that’s what traps the pressure. It could be damaged.
 
Westy

Westy

the teste
Nov 22, 2002
54,440
20,244
Sleazattle
There is a critical dimension between where the seal on the pump seals and when the valve is pushed open. A worn seal will let air pass before the valve can close, as will a weak spring in the valve.
 
rideit

rideit

Bob the Builder
Aug 24, 2004
23,342
11,511
In the cleavage of the Tetons
I have used all manner of shock pumps, new, old, cheap expensive. As a rule, I just always pump up a few PSI higher than where I want it to settle. Seems to be one of those 'just the way it is' things, but I sure would love a more accurate way.
 
canadmos

canadmos

Cake Tease
May 29, 2011
20,501
19,505
Canaderp
Most shock pumps out there seem to all be the same rebranded one...

I always find that the pressure changes when I attach the pump, not when I remove it.

But as jm mentions, maybe it's the valve in your shock that is bad?
 
canadmos

canadmos

Cake Tease
May 29, 2011
20,501
19,505
Canaderp
rideit said:
I have used all manner of shock pumps, new, old, cheap expensive. As a rule, I just always pump up a few PSI higher than where I want it to settle. Seems to be one of those 'just the way it is' things, but I sure would love a more accurate way.
Click to expand...
Shockwiz, but apparently that's what's wrong with the industry :p
 
6thElement

6thElement

Schrodinger's Immigrant
Jul 29, 2008
15,967
13,220
canadmos said:
Most shock pumps out there seem to all be the same rebranded one...

I always find that the pressure changes when I attach the pump, not when I remove it.

But as jm mentions, maybe it's the valve in your shock that is bad?
Click to expand...
The air in the shock has to pressurize the pump when you attach it.
 
MikeD

MikeD

Leader and Demogogue of the Ridemonkey Satinists
Oct 26, 2001
11,690
1,735
chez moi
Well my issue happens across two shocks and a fork and has always been this way, so I am guessing a new pump or adapter is what I need.

I have always just overpressurized and tried to unscrew it past the critical point as fast as possible; have used a lot more coil than air in my time tho, so I have apparently been doing something wrong and never known.
 
Last edited:
HardtailHack

HardtailHack

used an iron once
Jan 20, 2009
6,749
5,641
The valve core isn't loose? Maybe you can fit one with a shorter pin.

Also, why do people assume a digital gauge is better than an analogue one?
 
canadmos

canadmos

Cake Tease
May 29, 2011
20,501
19,505
Canaderp
HardtailHack said:
The valve core isn't loose? Maybe you can fit one with a shorter pin.

Also, why do people assume a digital gauge is better than an analogue one?
Click to expand...
Moar money = moar better, I'm guessing.

On the other hand, the measurement increments on some pumps is pretty garbage. I had a Pro (Shimano?) pump that had increments of 10psi. It was a wild guess as to what the actual pressure was.
 
MikeD

MikeD

Leader and Demogogue of the Ridemonkey Satinists
Oct 26, 2001
11,690
1,735
chez moi
HardtailHack said:
The valve core isn't loose? Maybe you can fit one with a shorter pin.

Also, why do people assume a digital gauge is better than an analogue one?
Click to expand...
Everyone seems bent on proving what shouldn't be happening, but absolutely and demonstrably does. I've never found a pump that can't drain the shock of air if you unscrew it to the right position and leave it there as the air passes out. There's *always* a point where the shraeder is held open slightly as it disengages. You can try to minimize it or ignore it, but it's there. Maybe every single valve I've ever used has been out of spec, but I doubt that.

The pump head with the lever in it makes the disengagement cleaner, near-instant, and very consistent.

And as 6th points out, the digital gauge is precise over any range of pressure where an analog is forced to compromise between range and precision (ed: and/or size of gauge face...). I don't need a digital because nothing I do is that precise, but there is a difference and it's not hard to understand.
 
6thElement

6thElement

Schrodinger's Immigrant
Jul 29, 2008
15,967
13,220
I like the lever to engage/disengage against the schrader that's a neat feature.

Okay, so now I need a digital with the lever.
 
R

roflbox

roflborx
Jan 23, 2017
3,163
834
Raleigh, NC
MikeD said:
So I keep reading people YELLING IN ALL CAPS ONLINE that no shrader valve shock pumps lose air when removing them.

This is odd, because if I unscrew the plain old shrader-thread head from my shock/fork using my Fox shock pump, the shock will fully deflate. So there's a demonstrable point of being partially engaged and losing pressure as I unthread it, fast as I might try to unthread quickly to avoid it.

I looked at a few fancy and not-fancy adapters supposed to cure this, but not sure more potential points of failure make sense. Plus there are new Topeak and other pumps with such features built in, and digital readouts that kinda make sense given the necessary precision with all this.

What do you guys use/think?
Click to expand...
I have one of these, they are quite nice:
www.topeak.com

POCKETSHOCK DXG

A precision fork and shock pump with an easy-to-read dial gauge for accurate pressure readings up to 360 psi / 24.8 bar. An air release button and Pressure-Rite connector makes setting proper pressure easy and eliminates air loss when disconnecting, while the flexible hose takes stress off the...
www.topeak.com www.topeak.com

There is a 2nd valve / connection that allows you to disconnect the pump with tiny tiny amounts of airloss
 
HardtailHack

HardtailHack

used an iron once
Jan 20, 2009
6,749
5,641
MikeD said:
Everyone seems bent on proving what shouldn't be happening, but absolutely and demonstrably does. I've never found a pump that can't drain the shock of air if you unscrew it to the right position and leave it there as the air passes out. There's *always* a point where the shraeder is held open slightly as it disengages. You can try to minimize it or ignore it, but it's there. Maybe every single valve I've ever used has been out of spec, but I doubt that.

The pump head with the lever in it makes the disengagement cleaner, near-instant, and very consistent.

And as 6th points out, the digital gauge is precise over any range of pressure where an analog is forced to compromise between range and precision (ed: and/or size of gauge face...). I don't need a digital because nothing I do is that precise, but there is a difference and it's not hard to understand.
Click to expand...
I think the only one I ever had a problem with was a lever type but it was a very old Topeak, I do agree that that is a good way to activate the valve.
Surely there is a screw down type that allows you to remove the Chuck in two stages?
 
MikeD

MikeD

Leader and Demogogue of the Ridemonkey Satinists
Oct 26, 2001
11,690
1,735
chez moi
I'm sure there is--do the newer topeaks have that? I'm pretty sure some of the external adapters do it just that way.
 
MikeD

MikeD

Leader and Demogogue of the Ridemonkey Satinists
Oct 26, 2001
11,690
1,735
chez moi
Guy I work with was an Air Force metrologist but specialized in electonics vice physical measurement.
 
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