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  1. #1
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    Pumping Up Brain Shock

    Is this typical when putting air into brain shock? Say I pump the shock up to 200 lbs with Fox pump, I then unscrew the pump off the schrader valve. I immediately screw the pump back on and it's like 15 lbs less. Does the air escape when screwing off the pump? If so then it means you always have less air than you think in shock? Or does it mean you have to add like 15 lbs extra to it?

  2. #2
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    I believe what you're seeing is the air flowing into the pump and tube when reattaching it to the shock. I see the exact same thing when attaching my Fox pump to my Reba.

    IE: pump the shock to the pressure you want and no worries.

  3. #3
    PVR
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    It is much easier if you have a shock pump with a pressure relief valve. This prevents the air from escaping when you unscrew the valve.

  4. #4
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    That is common of any air shock not just a brain.

    Try one of these...

    http://www.topeak.com/products/Mini-...PocketShockDXG

    Cheers!

    Edit: Guess I need to type quicker!

  5. #5
    DGC
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    shock pumps

    Quote Originally Posted by socal59
    Is this typical when putting air into brain shock? Say I pump the shock up to 200 lbs with Fox pump, I then unscrew the pump off the schrader valve. I immediately screw the pump back on and it's like 15 lbs less. Does the air escape when screwing off the pump? If so then it means you always have less air than you think in shock? Or does it mean you have to add like 15 lbs extra to it?
    If I remember right, on Fox pumps this is close to normal.
    What is happening is when you put a shock pump on a small volume high pressure bicycle shock, the pump gets filled with air and this is where the the pressure reading drops. The longer the hose and longer distance to the guage area, the more the drop in reading.
    If you want better readings, get a pump designed to lose minimal to no air.
    I have the Topeak DXG and use them in our shop all the time. This pump has a lock nut that keeps air from seeping out at the valve at any time, all that comes out is what is inside the pump. I usually run my shock about 165 psi., with my Topeak pump I get a 7 psi. lower reading if I put it back on right after setting it at 165. There are other pumps out there that may drop even less than the Topeak DXG.

    Finally, no matter the pump, go off of sag check first, ride feel second, pump reading third.
    OUCH...!!!!!!

  6. #6
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    Quote Originally Posted by Sid Nitzerglobin
    I believe what you're seeing is the air flowing into the pump and tube when reattaching it to the shock. I see the exact same thing when attaching my Fox pump to my Reba.

    IE: pump the shock to the pressure you want and no worries.

    ^
    +1

  7. #7
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    I guess I'll just go my ride feel. I think when you unscrew the pump you can't do it fast enough, although I would think the valve in the pump would just close up quicker than you can unscrew the pump. I figured a Fox pump for Fox shock would work perfect, but I guess not.

  8. #8
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    Quote Originally Posted by socal59
    I guess I'll just go my ride feel. I think when you unscrew the pump you can't do it fast enough, although I would think the valve in the pump would just close up quicker than you can unscrew the pump. I figured a Fox pump for Fox shock would work perfect, but I guess not.
    My experience so far has been that I'm not loosing any significant amount of air when disconnecting the Fox pump. The majority of the air you hear escaping when disconnecting is coming from the pump body and the hose not the shock (same as any tire pump I've used). When you reconnect the pump, the valve opens and air from the shock fills the pump body and hose causing a drop in pressure read at the gauge. Same thing happened w/ the Fox Float and Brain shock on the SJ Test Bike I had over the weekend.

    Anyway, yeah, the best approach is probably to pump it up to the pressure you think you need, ride it and adjust up or down from there. As long as you have a consistent reading before you start disconnecting the pump and a consistent amount of "missing" pressure when you reconnect it you're golden.

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