# Shock Pumps for low pressure



## jm2e (Mar 26, 2012)

Not going to post this thread in the suspension forum, because 99.9% of them won't understand/care.

Riding at 125lbs, my forks are set below 50psi. All shock pumps seem to be calibrated to go up to either 400psi or 300psi and if you look closely, they don't even have the correct number of hash marks below 50psi. (ie, there are 4 hash marks between 50psi and 100psi, each one representing 10 psi. Between Zero psi and 50psi there are only 3 hash marks). This makes it really confusing to figure out what pressure you're at. 
Meanwhile, My hubbie and I just noticed that in the 100-150 range, our two shock pumps (one Fox and one XFusion) read very similarly. Below 50psi though, and they're totally different. The Fox pump basically registers Zero pressure when there's still quite a bit left in there.

All this leads to a big frustration. Trying to dial in a fork can be pretty hard when very small differences in pressure are very discernible but your pump doesn't allow fine tuning or accurate measurement.

Wondering if anyone has thought much about this or noticed it or found a good solution.

Forks currently in use:
Fox Float 34 150mm
XFusion Sweep 160mm


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## JackJr (Sep 24, 2007)

My shock pump is just like yours. When I was setting up a fork for my 50lb son, I had to empty air out of the fork, compress it with the valve open to bleed all the air out, and then count the pumps as I filled it up - 10 - 20 pumps was about the range on that fork for him. The pressure really low - below 5lb - nothing on the gauge at all. This was a large volume Marzocchi fork that used low air pressures even with adult riders. Another option, you could replace the gauge, they are replaceable so you just need to find one that registers pressures in your range. Good luck.


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## supersedona (Dec 17, 2012)

Good idea(slapping forehead, really  ), why didn't I try that one sooner lol  Low(like tire range) gages are really common and generally cheap...


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## gmats (Apr 15, 2005)

Aloha, great question. I've faced this kind of stuff for work from time to time when the readings are not "mid scale" for the pressures I was interested in measuring.

You might try changing the shock pump's gauge.

The issue will be finding one small enough in size with the right fitting.

You can start here:

Utility Pressure Gauges, Air pressure gauge, Water Pressure Gauge

Good luck.


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## jeffscott (May 10, 2006)

jm2e said:


> Not going to post this thread in the suspension forum, because 99.9% of them won't understand/care.
> 
> Riding at 125lbs, my forks are set below 50psi. All shock pumps seem to be calibrated to go up to either 400psi or 300psi and if you look closely, they don't even have the correct number of hash marks below 50psi. (ie, there are 4 hash marks between 50psi and 100psi, each one representing 10 psi. Between Zero psi and 50psi there are only 3 hash marks). This makes it really confusing to figure out what pressure you're at.
> Meanwhile, My hubbie and I just noticed that in the 100-150 range, our two shock pumps (one Fox and one XFusion) read very similarly. Below 50psi though, and they're totally different. The Fox pump basically registers Zero pressure when there's still quite a bit left in there.
> ...


The simple answer is to put say a little bit of tape on the dial widow....the mark the tape with a pen, where you pump up to. If you think the shock needs more or less air than you can pump it up a bit more or less and mark that spot on the tape....

That method is the source of the saying dailing it in....

Anyway another way MAYBE to remove the hose and connection from the shock pump and simple attach the hose and fitting to a lower pressure floor pump....(depends on fittings)...

I would try dialing it in first.


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## miamia (Sep 6, 2014)

Hi
I have Marzocchi low pressure shock pump which max pressure is only 100 psi. I don't if they sell it anymore but with it you can dial the fork pressure quit accurately even near 20 psi mark.


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## jm2e (Mar 26, 2012)

Holy Mole!! Thanks a million!
Quick google search found one at Merlin Cycles for $50 bucks. Kinda steep for a shock pump, but worth it to dial in an expensive fork I think. Now, to buy enough other stuff to qualify for free shipping.....


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## Julie (Jul 26, 2005)

As a sub 130 lb rider, fully loaded, my biggest frustration has been finding a fork that performs well with less than 50lbs pressure without a $200 custom tune.


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## Brisco Dog (Nov 5, 2009)

I have this one and it works pretty well.

Fox Shox Digital Shock Pump > Accessories > Inflation > Pressure Gauges | Jenson USA


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## umicheng (Mar 24, 2011)

any ladies running a 150mm pike? would be curious of your settings...im sub130 too and am running 45psi with the rebound full out/fastest.


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## jewels (Mar 17, 2004)

on a 2015 pike dual air. (130 and 150mm) I'm 125, but prob 135lbs with camelback etc. I run 45 psi with rebound at 4 clicks out from the fastest. I tried at 50 psi, but prefer to run it at 45psi and use compression if I need it uphill, which I really never do. I try to match my front and rear shock about the same 'bounce/rebound' test. o ring shows good amount of travel used. Btw, Julie, this may be a fork to look at. It doesn't dive into corners with low pressure like some other air forks. Holds up nice and firm in corners but supple over bumps, I love this fork.


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## gmats (Apr 15, 2005)

jewels said:


> on a 2015 pike dual air. (130 and 150mm) I'm 125, but prob 135lbs with camelback etc. I run 45 psi with rebound at 4 clicks out from the fastest. I tried at 50 psi, but prefer to run it at 45psi and use compression if I need it uphill, which I really never do. I try to match my front and rear shock about the same 'bounce/rebound' test. o ring shows good amount of travel used. Btw, Julie, this may be a fork to look at. It doesn't dive into corners with low pressure like some other air forks. Holds up nice and firm in corners but supple over bumps, I love this fork.


This illustrates why having a gauge with enough resolution is helpful because there can be a difference at this kind of rider weight and shock pressures. Very minute adjustments can make a whole world of difference. I have seen applications (not bikes) where a large, 6" diameter gauge is used that sweeps from 0 to 10 psi because that kind of resolution is necessary.

And for others, this could/might be a need to put a shim into a shock to "lesson" the volume of the air chamber to prevent bottoming. The shim allows the lower pressure settings and the spring rate to ramp up quicker.


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## gsa103 (Sep 1, 2014)

Why not just use a standard floor pump? One of the main reason for a shock pump is that floor pumps start getting challenging to inflate at 140 psi. 

If you use short pump strokes you won't add a lot of volume and should be able to get closer with pressure. 

Alternatively, a standard automotive tire pressure gauge goes to 60 psi, and many have small bleed buttons. Inflate with any pump then bleed down.


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## miamia (Sep 6, 2014)

Hi
Bos Deville has quite large pressure range. Of course it depends what kind of bike you are putting the fork.
Floor pump won't work because when you remove the hose from the shock valve all the air will come with floor pump. That is reason why shock pumps have different kind of connection at the end of the hose.


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## umicheng (Mar 24, 2011)

thanks! I'll try that this weekend. I wasn't even aware of the dual air. I run the solo air...any performance gains other than the ability to ride at 130 or 150?


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## jewels (Mar 17, 2004)

I had the dual position air on my 26" revelation and was stoked to see it in the pike version. No performance differences inside, I also use an old marzocchi pump w/ low pressures.


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## Julie (Jul 26, 2005)

Great information Jewels. I've had my eye on one of those but figured it was just another "Holy Grail" as my friends that love the Pike are 200 lb guys. And I already know..just because it works for them doesn't mean it will work for me!


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## umicheng (Mar 24, 2011)

Hi Ladies - Hoping a couple of you could chime in to my latest post...potential issue with the pike? Thoughts? Not sure...I'm running 45psi and it's my first longer travel fork...but my 100mm locked out pretty solid and this pike is compressing about 30% if I stand up and bounce on the front of the fork....

Pike '14 - 150mm RCT3 - Not locking out?

Thanks!
Michelle


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## jm2e (Mar 26, 2012)

Took about a week to arrive from Merlin. Wonders of the modern world!


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