Air Shock Filling

[John Croucher]

I have a couple of motorcycles with air shocks.  What type of pump, hand/air compressor should be used to fill to the recommended pressures?

The front tubes can easily be filled to 60 psi with a small bicycle hand pump in two strokes.  But when removing the air chuck off the fill valve, the pressure leaks out faster than I can remove the air chuck.
The volume of air to raise the pressure is so small, it is quickly lost.

I have put the pump on the valve, pumped up, left the pump attached for 2 days and the shock will maintain the starting pressure.  So the shocks are not leaking down. 

When I used the air compressor set at 40 psi line pressure, the shock fills up, but leaks the small amount of pressurized air out instantly when removing the air chuck.

Any suggestion on how to fill and maintain the recommended pressures?  14-28 psi front,  60 psi rear.   

[Cdn850T5NT]

 I have air-filled frt susp. on my T5 (38mm fork tubes) with a cross-over /air pressure equalization tube. Seems to me you'd want to spice into a tube like that, fit a tee with a valve on the tee's branch and a Schrader valve on the other side of the valve. Mount valve solidly to the upper triple clamp... and I believe that'd do the trick.

[Tom H]

Harley has a hand pump for their shocks. My friend says it work great.

I seem to remember a tire valve that had a thumb screw on it. You would attach the valve and then turn in the screw, when done undo the screw and then the valve.

Tom

[John Croucher]

I have air-filled frt susp. on my T5 (38mm fork tubes) with a cross-over /air pressure equalization tube. Seems to me you'd want to spice into a tube like that, fit a tee with a valve on the tee's branch and a Schrader valve on the other side of the valve. Mount valve solidly to the upper triple clamp... and I believe that'd do the trick.

There is a common tube for both front shocks, one fill valve. All freshly rebuilt and as I mentioned, will maintain pressure, until the fill chuck is removed and the small shot of escaping air drops the pressure instantly. 

[John Croucher]

Harley has a hand pump for their shocks. My friend says it work great.

I seem to remember a tire valve that had a thumb screw on it. You would attach the valve and then turn in the screw, when done undo the screw and then the valve.

Tom

Sounds like a solution.  I though about leaving the pump attached and zip tying to the fork.  Allowing for pressure adjustments as needed. 

Any idea where this type of Shrader valve can be found?

[bigbikerrick]

Progressive suspension makes a hand pump that works real well. It has a "zero loss" type of connector ,if I remember correctly, so you dont lose much air when connecting and reconnecting. On a small volume application like  air forks I like to over pressurize it by a few psi, then I would use a small "slime" brand electronic digital gauge to fine tune it to get both sides the same.
I hope that helps,
Rick.

[hauto]

I have one of those HD pumps I'll sell you for $25.

[Tony F]

Look for a mountain bike suspension pump. They come with the zero loss valve and usually a pressure bleed button.

[Tom H]

This is kinda what I was thinking of as well as the no loss valve.

https://www.diymotofix.com/blog/how-to-make-a-shock-fill-tool-and-fill-station

Tom

[Perazzimx14]

You can also get a zero loss Schrader chuck like used for nitrogen filling shocks. 

[Ronkom]

I have air shocks on my Eldorado and had them on the EV I sold. After dealing w/the issues you describe w/my first air shocks years ago, I worked out a solution that has worked well on several bikes over the last 25 years. I mount a 2" 0-100 psi pressure gage and a schrader valve on the bike. both are piped into a line going to both shocks. This gives you more volume to work with (both shocks, piping, fittings & gage)   Pressure adjustment is a simple matter of hitting the schrader valve w/very quick bursts of air from any compressor. You just over shoot a little & bleed back to the exact pressure you want. You know both shocks are at the same pressure and you can check for any pressure loss over time w/a glance at the gage. In the pictures, the schrader valve has a metal cap (I cut a rubber gasket to fit inside)



 & is just above the tool box .
 

[John Croucher]

You can also get a zero loss Schrader chuck like used for nitrogen filling shocks. 

I am assuming this valve gets screwed on to the existing shrader valve.  Then additional plumbing to a second shrader fill valve.  After filling to pressure, the valve is closed and the input line from the second shrader valve is disconnected.  Acting as a manual check/backflow preventer.

The suggested bicycle-Progressive type pump is what I have.  The all have threaded fittings that allow leak down while removing.  The hand pump only requires two pushes of the pump handle to reach 30 psi.  Not very much volume.  It leaks down quickly.  As long as the pump is connected, pressure is retained. 

The above valve is around $25.  Plus additional hardware.  Would need two.  One for front and one for rear.  Space is also an issue on the front.  The valve is very close to the frame at full right lock. 

[Tom H]

John, look at my link on how to build what you need with the no loss valve.

Also do a search for what your looking for. When I did it, they seem to be about $50 to get one like you need ready to use. Ebay and Amazon have them.

Tom

[twowheeladdict]

There is so low volume that using an air compressor is not recommended.

[John Croucher]

Not quite. You only need one as it stay with the air source. You affix the IPS threaded portion to the air supply with a quick connect or threaded coupling. The you screw the other end to the Schrader, turn on the air supply then you screw in the t-handle to depress the Schrader to let the air into the shock. When the shock is filled to the required pressure unscrew the t-handle to close the Schrader unscrew the valve body from the Schrader and remove the assembly. Zero air loss.

You also have the option of fitting nitrogen bolts and in stead of using the zero loss chuck you use a hypodermic needle connected to the air supply to pierce a bolt with a rubber insert in it and inject the air in. Pull the need out and it self sealing. Needles are $3 for 6 at tractor supply and a 1/8" compression x 1/4" female adapter and a compressed air quick connect are all you need.


You can also add an inline pressure gauge with some pipe nipples and a tee or simply affix the zero loss chuck to one of these that has a screw threaded air chuck.












 

Got it.  I did not think about the t handle pushing in and releasing the shrader valve sealing plunger.  So the only air lost is the small amount inside the valve body after the t handle is screwed out and the fill valve released.   I will order one of these today and give it a try.  Thanks for the help. 

With the very small volume of air required to fill a shock, it make me wonder how many riders "thought" they were filling and "retaining air" in the shock.  It was very obvious to me that there was pressure with the pump attached and no pressure when it was removed and the small "pisssss" was heard.  And obvious with the amount of sag. 

[Dukedesmo]

Quote from: Tony F on February 23, 2020, 06:14:38 PM

Look for a mountain bike suspension pump. They come with the zero loss valve and usually a pressure bleed button.

___________________ ___________________ ___________________ ___________________ ___________________ _____

Agreed, unless the volume of air is so much greater than a bicycle pump can deliver?

I have a couple of MTBs with air shocks/forks and it takes no time at all to accurately get 100+ psi into them, I did consider using the compressor but it would likely overfill too easily.

The pumps are also small enough to carry on the bike and are inexpensive.

[Vagrant]

when I had them I just filled the air compressor tank to the PSI I wanted then filled the fork with a standard chuck. virtually no loss but you need to be home to do it.

[Perazzimx14]

There is so low volume that using an air compressor is not recommended.

Volume and pressure are not the same. Also how would you get air into the shock if you did not use some some of air compressor? 

[twowheeladdict]

Volume and pressure are not the same. Also how would you get air into the shock if you did not use some some of air compressor?

You know what I am talking about, but I will humor you. Pulling up to a gas station air compressor where it puts in air until you let go could easily overfill the shock because it will take less than a second to exceed the recommended psi. Same for a home compressor. Now a portable digital compressor with an automatic stop when the desired psi is reached might work, but then there is the loss when disconnecting. Not as critical with one full for both shocks, but not a good way to fill individual shocks accurately.

[Perazzimx14]

You know what I am talking about, but I will humor you. Pulling up to a gas station air compressor where it puts in air until you let go could easily overfill the shock because it will take less than a second to exceed the recommended psi. Same for a home compressor. Now a portable digital compressor with an automatic stop when the desired psi is reached might work, but then there is the loss when disconnecting. Not as critical with one full for both shocks, but not a good way to fill individual shocks accurately.

I'm guessing you are not familiar with pressure regulators?






 

[twowheeladdict]

I'm guessing you are not familiar with pressure regulators?

I am, but would rather follow the manufacturer recommendations about using a zero loss hand pump than an electric compressor.

I have also adjusted my shocks on the road because of changing conditions. Do you carry your pressure regulator to the gas station?

[Vagrant]

going back in time assuming my memory is correct the same shocks were used on an HD and a wing. one was a max of 20# one 40# so I wouldn't be too concerned about blowing them up.

[Perazzimx14]

I am, but would rather follow the manufacturer recommendations about using a zero loss hand pump than an electric compressor.

I have also adjusted my shocks on the road because of changing conditions. Do you carry your pressure regulator to the gas station?

Wow I cannot imagine how much riding time you lose if you stop to adjust the suspensions air pressure everytime the road surface changes. Be glad you don't live in Pennsylvania you never get anywhere because you'd be continually adjusting the suspension

Riding on/off pavement highway or single track loaded or unloaded I don't even adjust the air pressure in my tires let alone fool with the suspension settings. I just ride.   

[twowheeladdict]

Wow I cannot imagine how much riding time you lose if you stop to adjust the suspensions air pressure everytime the road surface changes. Be glad you don't live in Pennsylvania you never get anywhere because you'd be continually adjusting the suspension

Riding on/off pavement highway or single track loaded or unloaded I don't even adjust the air pressure in my tires let alone fool with the suspension settings. I just ride.

That explains a lot.

[Perazzimx14]

That explains a lot.

 

[Ncdan]

I dealt with this issue for years with the CB Honda’s which had air assist forks with a 14lb max and one could easily blow out the seals.
Simple fix. I set my compressor for a 20lb max limit and just bump the chuck to the air fitting until when I checked with the gauge I had the amount I wanted. The secret to the process is when checking to make a good solid connection as to not lose and air during the checking process.

[John Croucher]

 A soda/beer can has 40-50 psi before opening.  The fast pop lets the small volume of pressure out very quickly.  Using a zero loss air chuck looks like the best option to get a good fill.  There are several bicycle air shock pumps available with the zero loss valves.  Have to get one and try it out. 

[Ncdan]

A soda/beer can has 40-50 psi before opening.  The fast pop lets the small volume of pressure out very quickly.  Using a zero loss air chuck looks like the best option to get a good fill.  There are several bicycle air shock pumps available with the zero loss valves.  Have to get one and try it out.

Issue with the bike pumps is getting to the valves location on a MC can be impossible to get to. It’s that way on my Honda CB1000c with air assist shocks and forks.