I have written 125psi in my notes, most likely from a Fox rebuild guide.

 

Bike Help Center | FOX

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I had the 2021 x2 up, that one is 100psi

 

Thanks for your reply guys. I'm guessing this is filled up with regular old free air and not organic, small batch, free range, halal nitrogen?

 

If you want air to be ingested into the damper then use 125psi, if you don't then go higher.

 

Well I was running it 60PSI for a long time =/. Also it looks like I'm loosing 25PSI each time I disonnect my pump so gonna set it to 150 before I take the pump off.

 

The recommendations are silly low and one of the main reasons these shocks suck in air.

 

Does a higher IFP pressure result in any firmer damping?

 

No, it will make a fraction more spring force but that's it

 

Why would FOX reccomend such low ifp pressure in the first place ?

What pressures are you all using ?

Thanks

Richie

Higher IFP pressures prevent cavitation and air ingress into the damper. But they cause more seal friction and more preload. The effect on spring-rate is minor. The one I measured was 10lb/in.

Lower IFP prssure makes them feel all nice and smooth and sensitive in a push test. That is all.

 

Why would FOX reccomend such low ifp pressure in the first place ?

What pressures are you all using ?

Thanks

Richie

 

2016-2018 is 125 psi
2019-2020 is 125 psi
2021 is 100 psi

You can find that info in the Float X2 rebuild guides for the model year of the shock - Bike Help Center | FOX

The PSI values for the piggyback are a little hard to find in the documents based on how Fox lays it out but if you Ctrl+F/search in browser for 'IFP' you will find it.

 

So what do you fellas think the 2021 shocks should have if 100psi is too low?

 

2019-2020 FLOAT X2 Rebuild | Bike Help Center | FOX

www.ridefox.com

Step 12 - Release the nitrogen charge by depressing the Schrader valve within the reservoir.
Step 29 - Fill the IFP chamber to 125 psi (8.6 bar) with your shock pump, then install the reservoir end cap, tightening to 30 in-lb (3.4 Nm) with your 6mm hex wrench.

So it comes from the factory with nitrogen but you refill it with air after servicing? What's the purpose of nitrogen, does it really matter?

 

2019-2020 FLOAT X2 Rebuild | Bike Help Center | FOX

www.ridefox.com

Step 12 - Release the nitrogen charge by depressing the Schrader valve within the reservoir.
Step 29 - Fill the IFP chamber to 125 psi (8.6 bar) with your shock pump, then install the reservoir end cap, tightening to 30 in-lb (3.4 Nm) with your 6mm hex wrench.

So it comes from the factory with nitrogen but you refill it with air after servicing? What's the purpose of nitrogen, does it really matter?

Nitrogen is way more convenient on a production line. That's it.

 

What was the reason for older shocks like the DHX 5.0 to feel so drastically different with higher IFP pressure? I'm not sure about how much noticeable affect ifp pressure has on newer shocks but certainly my old dhx where you adjust the ifp pressure with a shock pump made huge difference to feel...what felt like more damping...all the way through the stroke.

 

The DHX5 ran a "Boost Valve" which was like the SPV that Manitou (and CVT that 5th Element) ran back in the mid 2000's. It was pressure sensitive damping. More pressure closed the base-valve more.

 

2022, 175 psi. Fox numbers are stupid low.

 

Does this also remain true for IFP pressure within a DHX2?

 

Wouldn't think so, as there's no pressure on the other side of the shaft seal. I think that's the worry with the FX2, since the max air sleeve pressure is so much higher than the IFP pressure.

 

Not correct. The IFP separates oil and the air / nitrogen charge in the damper so regardless of what spring is used, air or coil, damper function will be the same during compression and rebound.

My experience is that lower IFP pressure will lead to lower lockout force, softer compression damping but also more movement of the IFP, which will eventually cause wear and leaking of the IFP seal.

 

and since the X2 and Float X2 are twin tube shocks, none of your points apply in this case. Besides that, what @seitenryu said.

 

Sorry, should have red seitenryu’s post more carefully. I have not played with IFP pressure in a twin-tube shock, but I can see how the shaft seal could potentially leak though wouldn’t this only happen if the IFP pressure was much higher than the air spring pressure, so not really an issue on the X2 but could be on the DHX2?

 

Everytime the main shaft seal gets a pressure reversal it can pump some air.