2 fox float air pumps, two totally different readings.

[CO 2.0]

So I have a regular style air pump from fox that came with my sno pro. Also have a high flow pump that came with my float evol R's. The high flow pump is showing 55psi while the regular pump is showing 65psi on my front main chambers. Why would this be so different? Guess one of the pumps is jacked up?

 

[boondocker97]

I would guess they are both fine. The reason you see such a large drop on the high volume pump is that when you hook it up to the shock, it takes more air from the shock to fill the pump up initially than the small one. I don't know what the voulume difference is between the two pumps, but It doesn't surprise me that it would drop 10psi. My standard pump drops a couple psi itself. When you are dealing with such small volumes at high pressures, it doesn't take much of a change in voulume to change the pressure significantly.

If you press the air valve on your air shock when it is set at 150psi, you immediately loose most of your pressure. If you did the same to a tractor tire that had 150psi in it (not that it would in the first place) you would be lucky to drop a pound.

 

[mezz250x]

Do both your pumps go up to the same pressure? They have two different styles, one for main chamber pressures that only goes up to 150psi, and one for the EVOL chambers that reads up to 300psi. That will make a difference. Make sure you are using the right one, so if your shock is only sposed to hold 150psi, ONLY use 150psi gauge on it. Also make sure the sled is off the ground when checking/changing air pressures. I see alot of people complaing that there shocks are messed up cause the pressure changes all the time, but they check it in the garage before a ride, then check it on the mountain full of snow and its different.....duh, more weight on the sled will do that.

 

[CO 2.0]

I always check pressure with the sled off the ground. The initial readings show 10psi different between pumps when I hook them both up. Obviously reading from the 150psi side of the hi flow gauge. The main chambers in my shocks only drop a couple psi when I disconnect either pump. Something just doesn't seem right. Gonna grab a buddies pump and check pressure with it to see which of mine is reading different.

 

[ndC7M8]

I always check pressure with the sled off the ground. The initial readings show 10psi different between pumps when I hook them both up. Obviously reading from the 150psi side of the hi flow gauge. The main chambers in my shocks only drop a couple psi when I disconnect either pump. Something just doesn't seem right. Gonna grab a buddies pump and check pressure with it to see which of mine is reading different.

they shouldn't drop when you disconnect the pump. It should drop a pound or two immediately when you hook the pump up as the hose & pump are being filled but the schrader valve shouldn't let any air out when you unhook, since it is re-seating when you unscrew the hose fitting.

As far as changing pressure, are you setting your evol chamber to where you want it first, then checking the main chamber?
Are you using the smaller gauge on the backside of the high pressure evol pump for the main chamber pressure, or are you just using your old Float pump to check main chamber pressure? You should just use the new pump on the high scale for evol chamber, then flip it around to the scale on the back when you set main chamber.
I haven't hooked my regular float pump up to my main chambers on my evols but I'll give it a try, maybe its a difference in the pumps internally, since they're meant for different types of shocks?

 

[CO 2.0]

they shouldn't drop when you disconnect the pump. It should drop a pound or two immediately when you hook the pump up as the hose & pump are being filled but the schrader valve shouldn't let any air out when you unhook, since it is re-seating when you unscrew the hose fitting.

As far as changing pressure, are you setting your evol chamber to where you want it first, then checking the main chamber?
Are you using the smaller gauge on the backside of the high pressure evol pump for the main chamber pressure, or are you just using your old Float pump to check main chamber pressure? You should just use the new pump on the high scale for evol chamber, then flip it around to the scale on the back when you set main chamber.
I haven't hooked my regular float pump up to my main chambers on my evols but I'll give it a try, maybe its a difference in the pumps internally, since they're meant for different types of shocks?

Maybe the pressure drop I'm seeing is the pump letting out pressure and when I reconnect it takes a couple psi from the shock to fill the pump up again? I am starting at the evol chamber, then setting the main.

 

[ndC7M8]

Maybe the pressure drop I'm seeing is the pump letting out pressure and when I reconnect it takes a couple psi from the shock to fill the pump up again? I am starting at the evol chamber, then setting the main.

That should be exactly right. I cant seem to be able to access an online manual for the shocks but I remember reading that you will see a slight drop in pressure when you connect your pump to the chamber. Once you set your pressure it should stay there.

Say you set your main chamber pressure at 90psi. At that point you have 90psi in both the main chamber and the pump. So there is 90psi behind the schrader valve and as long as you unscrew the pump quick so it can re-seat it really wont be releasing any air (maybe just a tiny bit, but it would be in terms of micro-adjustment as far as those shocks go).

The air pressure you're hearing escape would then be the said 90psi that is still in the pump. Its just that quick burst because of how small the pump is.

 

[CO 2.0]

Thanks for the help. Still shows 10psi different between the 2 pumps no matter what. It's pretty obvious if you were here doing it yourself. I've delt with and serviced my fox air shocks for years so I know when there is an air issue with these kind of shocks. I need a third pump to verify. Only thing that is gonna help me at this point.

 

[av8er]

check it with a good tire gauge

those pumps that come with the sno pro are mass produced and cheap, Made in China probably

 

[Johnmaster]

You could try it on a larger volume chamber like a car tire. A little squirt of air released isn't going to change that reading much.