When I go over a sidewalk, the marker ring on my shock goes all the way down the shock, so I think I need air.

I bought a Giant "shock pump" that supposedly goes up to 400 psi. I screwed it onto my read Fox Shock, on my 2019 Giant Trance 2. The gauge on the pump reads 0. Shouldn't it be reading some air pressure, if there was air in my shock?

Then I started giving it some pumps. It resisted quite a bit. One pump it went up to 50 psi on the gauge. 2 pumps and it went up to 100. Then I can pump all day and it won't move beyond 100.

I don't think air is actually going into the shock. Is there some trick to this? I read over the manual and it just tells me to fill it with air, but there are no specifics.

Screenshots of my attempt: enter image description here enter image description here

  • The red thing seems to spin.
  • The blue thing seems to have 3 positions: down, right and left.
  • Where the pump is connected is the only place I see to make such a connection. * If I screw it SUPER tight, I read 200 psi on the gauge, but it will still not accept more air no matter how much I pump.
  • Can you please add a photo of the shock, with your pump attached? I have a suspicion you're into the negative air side of the shock. A shock pump is the right tool here, so good start.
    – Criggie
    Jun 16, 2019 at 1:09
  • 1
    @Criggie Added screenshots and a bit more description following another attempt. Jun 16, 2019 at 2:21
  • Did you have to remove a cap/lid to access that valve ? Or has it always been open and exposed ? Maybe there's mud/grit in the valve ?
    – Criggie
    Jun 16, 2019 at 20:45
  • It had a cap that I put in my pocket Jun 16, 2019 at 23:15

1 Answer 1


The blue thing is a 3 position lever, which controls how fast the air moves between the two chambers. Looking at it directly,

  • LEFTmost position is FIRM, ie pointing at your drive side.
  • MIDDLE position (ie straight down) is MEDIUM
  • RIGHTmost position is OPEN, ie pointing to your left while riding.

(There's a chance I have that backward. Test it out first)

So you need to set the lever to OPEN, and set the sag on your rear to about 25% when you're sitting still on the bike, with all your normal riding gear. This is easier with 2 people.

You can press the small black nubbin on your pump to release air from the shock. Its straight below your gauge in the first photo. A brief press should make a Hiss and allow air out.

Some shock pumps have a two-stage connector, where the first thread engages the outside of the schrader connector, and then the second slowly lowers a "presser" into the release in the middle of the valve. This is to minimise pressure loss when connecting and disconnecting the pump.

At this point you should be able to release air from the shock, and add more by pumping.

I can't find your pump model - the nearest Giant is https://www.giant-bicycles.com/nz/control-mini-shock-1 but that looks quite different.

The manual for your shock is at https://www.ridefox.com/dl/bike/605-00-139-FLOAT-DPS-Tuning-Guide-white-revB.pdf

  • 1
    I had similar on a tire not so long ago, after checking with 3 different pumps it turned out to be Schrader valve at fault. Wouldn't let air in or out. Had to get a valve tool and unscrew the valve. Might not be the issue the OP has but Schrader's are prone to this for some reason
    – Dan K
    Jun 16, 2019 at 8:19
  • 1
    I put the position level to the right. i.e the left side of the bike while riding and tried to pump more air in and the pressure wont go up. it just makes it harded to unscrew the pump from the valve, and it lets a little "pff" out when I do. I think the air is only in the pump hose and not going into the shock. I'll bring it to the shop tomorrow. They are closed today :/ Jun 16, 2019 at 15:24
  • 2
    Store switched out the pump. A different one worked fine. Jun 18, 2019 at 3:34

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