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Trying to get more air in my shock and forks as I'm a fat biffer now and I can't unscrew the pump from the valve fast enough to not lose the air.
Is there a shock pump with some sort office release connection like you get on a lot of tyre pumps?
I'm definitely losing pressure from shock as when I then check sag it is more than before I started trying to add more...about 1 in 5 times I get enough air back in to be back to what it was, but I can't add more air.
Ta.
Can't believe folks still think it's air in the shock escaping. The valve closes before you get anywhere near taking the end off. The only air escaping is from the tube.
When you put a pump on and the pressure seems low, it's because air has filled the tube.
Unscrew at your leisure fam. Makes no odds. 👍
Sure you're losing air from the shock and its not just the pressure in the pump releasing?
Syncros has a screw on the adaptor to seal the rest of the tube off
https://images.app.goo.gl/npfVyhVTnPBrdAUu5
We have had one for a few years and it works well
Going by the amount of sag before and after, definitely from shock not pump.
Are you exceeding the max pressure of the shock?
Topeak make a nifty little check valve for just such a purpose.
BETO do a pump with a dual stage head. You screw the main attachment on and then screw in a red dial to press the valve plunger.
My old Bos shock was a pita for letting air out when detaching the hose and the BETO pump solved the problem
I have the same as Tracey and it works really well.
I have the Beto and I can't seem to get that unscrewed quick enough...it is stiff/tight...I'm just unscrewing should I be doing something as well as unscrew? Maybe push pump head down on shock valve?
DickBarton
Member
I have the Beto and I can’t seem to get that unscrewed quick enough
Nothing to do with speed, there's 2 steps to it. You unscrew the middle knob and that closes the valve. Then when you unscrew the pump from the valve you'll hear some air escape, but it's not escaping from the shock- it's already sealed. It's escaping from teh pump, which was at the same pressure as the shock.
All shock pumps worthy of the name do something like this. And those aftermarket add-ons are absolute bullshit, for the same reason.
Topeak make a nifty little check valve for just such a purpose
I've got one but I found I couldn't trust the pressure the gauge was reporting and sometimes I'd barely put any air in and it was reporting very high pressure. Take it off and seemed normal.
And then realised the air releasing was just coming out of the pump anyway.
As for OP, if the shock has more sag than when started, then you have a leak in the shock, in my opinion. When was it last serviced?
Can’t believe folks still think it’s air in the shock escaping. The valve closes before you get anywhere near taking the end off. The only air escaping is from the tube.
When you put a pump on and the pressure seems low, it’s because air has filled the tube.
Unscrew at your leisure fam. Makes no odds
My shocks disagrees 100% with the above, removing the pump drops 7-8psi. I have no reason to doubt it.
How are you measuring a 7/8psi loss in your shock over this event ?
As above, when you unscrew the pump, the air in the hose and the pressure gauge escapes. That's the hiss that you hear. It's not air escaping from the shock.
Then, when you reattach the pump, some air is released from the shock to pressurize the hose and gauge. This means that the pressure reading will be lower after you reconnect a pump than when you previously removed it.
This is completely normal and has been explained on forums over and over again for decades.
A quick release fitting will not help because you still need to pressurize the hose and gauge before you can use it, so the pressure has to drop in order to connect a gauge, that's just basic physics. Problem with a quick release is that it probably wouldn't fit a lot of forks where the valve is recessed into the fork crown.
My shocks disagrees 100% with the above, removing the pump drops 7-8psi. I have no reason to doubt it.
How do you measure this drop in psi? By attaching a shock pump again or some kind of pressure gauge?
That's where you lose your pressure as the air has to charge the system/fill the hose to work.
You cannot measure the air pressure with a shock pump attached, remove the shock pump, then reattach the shock pump and expect to get the same reading. The hose has to fill with air from the shock in order to work.
As you unscrew the head, the Schrader valve pin moves outwards and seats in the valve body thereby stopping any airflow from the shock(or inner tube). The air loss you then get(the pressure in the hose is the same pressure as the shock/inner tube) is the air escaping from the hose, not the shock/inner tube.
Sometimes you can have a bad connection where the valve pin is slightly depressed but the connection isn't airtight, but that is really only in the realm of quick release valve attachments. Screw attachments should make this impossible.
Surely it's easy to check where the air is coming from.
Screw the pump on, set your shock to a normal pressure, then unscrew it to the point where you hear air escaping and leave it to do so until the hissing stops. If the air's only escaped from the pump, it should only hiss briefly and your shock should support your weight. If if's escaped from the shock then you should hear rather more air escaping and your shock should end up completely flat.
Have you tired turning the whole pump / hose / connector rather than just the connector?
That’s how I connect / disconnect my shock pump.
How do you measure this drop in psi?
The shockwiz dynamically shows the pressure, when you remove it the pressure drops via the App.
Sometimes you can have a bad connection where the valve pin is slightly depressed but the connection isn’t airtight, but that is really only in the realm of quick release valve attachments. Screw attachments should make this impossible.
have had this happen on forks with a screw on shock pump.
Bez the killjoy, ruining my favorite internet argument with completely logical way to test the hypothesis.
Air shocks / forks with negative chambers will reduce the positive air pressure once +/- are equalised.
My BETO extra screw thing pump works very well.
So if you have live data.....put in an extra 8psi.
Another point in The more info you have the less you know
Going by Bez's suggestion, the hissing doesn't stop quickly. I'm convinced I'm not getting the connector unscrewed quickly enough to get the pin reset to seal the shock.
Likely to be my technique in unscrewing the pump.
It could be the valve core in the shock is knackered?
The pin should disengage before the seal to outside is broken .
One of my pumps has an adjustable pin.
Other option is as Phil says the shock valve core could be damaged or not quite fully screwed in.