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· Registered
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Discussion Starter · #1 ·
I am tired of my Giant brand shock pump. I've been using it for years. It releases too much air on release and the pressure gauge seems off.

I've searched the forum and looked on Amazon. Nothing blows me away -- ha!

Does anyone have one that they just love? Doesn't release too much air and has an accurate gauge?

Thanks in advance!
 

· All Mountian Destroyer
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that pressure release when you disconnect isn't actually releasing air from your fork's air chamber. I'll look for the article I read but let me see about explaining the order of operations myself...

Screw nozzle at end of pump hose onto schrader valve on fork air chamber ->

Seal is created between o ring on pump screw nozzle and valve stem ->

Screw the pump on further to open the Schrader valve and pump allows air in from air chamber and displays pressure as one large air chamber, this could be lower by a few PSI from when you last pumped up because the pressurized air had to fill the new regular atmosphere pressurized volume in the hose and pump body ->

You pump up to the proper PSI with the pump body and air chamber fully connected as one air chamber ->

Unscrew the pump and the first thing that happens is the Schrader valve closes before the exterior o-ring seal is broken, you now have the exact psi you pumped up to in the air chamber sealed by the schrader valve, and the pump body at the same pressure sealed by the o-ring on the nozzle ->

as you unscrew the remaining amount you will hear a puff of air but this is simply from the air inside the pump and tube venting as it is at a high PSI and once the O-ring seal is broken it needs somewhere to go, this air does not come from the fork air chamber since the schrader valve was closed first ->

as i mentioned earlier you will lose a few PSI when you put the pump back on because the pump itself adds volume to the system and needs to equalize the pressure.

I completely understand if the gauge is off and you want to replace for that reason, I've loved my Fox brand one, it has more metal and less plastic than some of the other ones and has held up well. I do wish i had a digital gauge sometimes though.

If you truly are losing pressure maybe check the schrader valve core, could be gunked up or old. Perhaps replaceable during suspension service.

Let me know if this made any sense, i'll look for the article in the meantime.
 

· Registered
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433 Posts
Discussion Starter · #6 ·
that pressure release when you disconnect isn't actually releasing air from your fork's air chamber. I'll look for the article I read but let me see about explaining the order of operations myself...

Screw nozzle at end of pump hose onto schrader valve on fork air chamber ->

Seal is created between o ring on pump screw nozzle and valve stem ->

Screw the pump on further to open the Schrader valve and pump allows air in from air chamber and displays pressure as one large air chamber, this could be lower by a few PSI from when you last pumped up because the pressurized air had to fill the new regular atmosphere pressurized volume in the hose and pump body ->

You pump up to the proper PSI with the pump body and air chamber fully connected as one air chamber ->

Unscrew the pump and the first thing that happens is the Schrader valve closes before the exterior o-ring seal is broken, you now have the exact psi you pumped up to in the air chamber sealed by the schrader valve, and the pump body at the same pressure sealed by the o-ring on the nozzle ->

as you unscrew the remaining amount you will hear a puff of air but this is simply from the air inside the pump and tube venting as it is at a high PSI and once the O-ring seal is broken it needs somewhere to go, this air does not come from the fork air chamber since the schrader valve was closed first ->

as i mentioned earlier you will lose a few PSI when you put the pump back on because the pump itself adds volume to the system and needs to equalize the pressure.

I completely understand if the gauge is off and you want to replace for that reason, I've loved my Fox brand one, it has more metal and less plastic than some of the other ones and has held up well. I do wish i had a digital gauge sometimes though.

If you truly are losing pressure maybe check the schrader valve core, could be gunked up or old. Perhaps replaceable during suspension service.

Let me know if this made any sense, i'll look for the article in the meantime.
This is very interesting and makes sense. The thing that concerns me is say I pump to 220 in psi on the pump gauge. Then because I'm cautious I check that pressure with my Topeak digital gauge and it says 208. Is the pump gauge inaccurate, air released when I disengage the pump, air lost when I engage the Topeak gauge, or all of the above?
 

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You lose air when engaging the hose and shock. Air from your shock fills the hose and pump, typically about 10 psi worth. After you pump it up, when you unscrew it, you just hear the air from the pump and hose being released. It disengages from the shock before the seal to the pump hose is broken.

FYI - You can screw your pump on until it almost engages with the shock (enough to make a seal, but not enough to engage)... and then pre-pressurize your pump to the amount of air that should be in your shock. Then when you fully screw it on, you don't lose air from your shock.

I've got a Giant and a Shimano shock pump that are decade + old, and still work just fine. I guess I never cared how accurate they were. I just keep pumping until it feels right, and that's the psi it is. Consistency is all I care about. Same with tire pumps. I go by feel.

Lezyne is probably the gold standard for most pumps.
 

· All Mountian Destroyer
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This is very interesting and makes sense. The thing that concerns me is say I pump to 220 in psi on the pump gauge. Then because I'm cautious I check that pressure with my Topeak digital gauge and it says 208. Is the pump gauge inaccurate, air released when I disengage the pump, air lost when I engage the Topeak gauge, or all of the above?
I would guestimate the pump gauge is innacurate. What I do is find 2-3 sag settings that I like for different scenarios and make a small mark with a sharpie on the dial of my shock pump. Even if the number of the dial is "wrong" I still get the same pressure every time for predefined ride characteristics. Although this is not the best when trying to dial things in or transfer settings to other forks.

220 psi is a lot of pressure, and the air cartridges in all honesty aren't large. If you let air escape even in the small amount of time it takes for the topeak gauge to make a firm seal I could see you losing some PSI in the process. What PSI is your topeak gauge good up until? I'd imagine most of the non-road ones would max out around 80?
 

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Discussion Starter · #9 ·
I would guestimate the pump gauge is innacurate. What I do is find 2-3 sag settings that I like for different scenarios and make a small mark with a sharpie on the dial of my shock pump. Even if the number of the dial is "wrong" I still get the same pressure every time for predefined ride characteristics. Although this is not the best when trying to dial things in or transfer settings to other forks.

220 psi is a lot of pressure, and the air cartridges in all honesty aren't large. If you let air escape even in the small amount of time it takes for the topeak gauge to make a firm seal I could see you losing some PSI in the process. What PSI is your topeak gauge good up until? I'd imagine most of the non-road ones would max out around 80?
The max pressure on the Topeak is 250. But yes I'd imagine even a split second will allow 10-20 lbs escape under such high pressure.
 

· high pivot witchcraft
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If you are still looking for a new pump, the old mantra here is that all of them come out of the same factory and are basically the same.

I have a 4 or 5 year old digital RockShox, which is identical to the Fox version, save and except for the logos. It’s worked well so far for me. Pretty much flawless. Nothing bling except perhaps the digital readout but I would not hesitate to buy it again. I think it was $100 CDN less 25% = $75 CDN. Light, stealth, carryable, accurate (as far as I know), and still using the original battery through annual 4 season usage.
 

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This pump is the ultimate. I bought it as a home shop pump and planned to take mini pumps with me away from the house but I like it so much that I'll transport it just in case. After using a floor pump it'll make your mini pumps feel silly.

 

· Elitest thrill junkie
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41,081 Posts
I hate shock pumps, they all suck. Stupid flexible hose that eventually breaks over time. Hard as hell to pump when the pressure gets high (so you try to grip it harder and break said hose). Most of them are all the same ones, with different pressure ranges.
 
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· Registered
Beers. Bikes. Battlestar Galactica.
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I recently bought a Topeak DXG XL (with the braided hose). Used to have the smaller one with the rubber hose and that worked great but was really hard to pump up at higher pressures. The bigger one makes things much easier and it's still small and light enough to chuck in a bag if you need to.

The "Pressure-Rite" connector works well and is really simple. The thumbscrew controls the position of the needle inside the pump. You wind it all the way off (anti-clockwise) and screw the nozzle onto the shock valve. At this point, even with the nozzle fully tightened, the shock valve is still closed but the pump has created an airtight seal around it. Now you tighten the thumbscrew (clockwise), which moves the needle down the nozzle until it pokes the shock valve open and you get a reading on the guage. When you're done pumping just undo the thumbscrew to close the shock valve again and then unscrew the nozzle. The only air that escapes is whatever is left inside the pump.

You can even buy service kits/spare parts for them, so not something you'll need to throw away in a year or two. I think £50 is pretty reasonable too.
1944378
 

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I hate shock pumps, they all suck. Stupid flexible hose that eventually breaks over time. Hard as hell to pump when the pressure gets high (so you try to grip it harder and break said hose). Most of them are all the same ones, with different pressure ranges.
Agree... most kinda suck, and yeah, most are the same pump. I've even interchanged parts between three different pumps once to get one working one... one branded Fox, one RockShox, and one no name that came with a bike. Tubes, handles, and gauges looked different, but internals 100% identical. Wound up with a Fox gauge on a RockShox tube and no name internals.
 

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I am tired of my Giant brand shock pump. I've been using it for years. It releases too much air on release and the pressure gauge seems off.
As others said, the air you hear is air escaping the tube and pump, not the shock or fork itself. As for the gauge being off, it's irrelevant really. You add or remove air to reach a particular sag on your shock and forks, not to reach a specific pressure. Set you sag, and take note of the pumps reading for future checks. It's just a reference point.
 

· Out spokin'
In cog? Neato!
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I've owned quite a few... maybe a dozen over the years... Rock Shox, Marzocchi, Fox, BikeYoke, others.
Here's the one I carry in my Wingnut: the Birzman Macht. It's tiny & weighs only 84g yet the gauge seems accurate enough and the air release valve (button on the back of the gauge) works a charm.
1944391

But this is really just for on-bike use. At home I use the larger, heavier duty shock pumps.
=sParty
 
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