Anyone worked with air shocks ?

[rcx132]

I've finally received my Fox 2.0 air shocks and started fitting to my buggy.

I've done some basic reading on how they work but still have a lot to learn about them so this is just the start of the journey.

I had hoped I could depressurise them so that I can cycle the suspension and check nothing interferes (I have 18" travel so things are tight!). But now I'm reading deeper into the subject I'm hearing that I shouldn't depressurise or do anything myself because the oil can cavitate and needs to be factory bled.

Can I at least slightly depressurise them to get the car to sit at ride height so I can continue working on the build?

I bought them from the official UK dealer so I should be able to get official support.

I borrowed nitrogen filling equipment as I thought I could tune the shocks myself.

 

[Shox Dr]

NO,NO NO. I'll regret it.

Edit. Typo YOU'LL regret it

Il

 

[knighty]

how about fit them, and add a small ratchet strap around each one contracting it and reducing ride height?

might have to add some weight or jack each wheel up and you put the ratchet strap on

 

[rcx132]

Edit. Typo YOU'LL regret it

Would you give some insight? What if I depressurise and drain them to do the build and then have them professionally set?

To initially test the suspension I made these fake mock up shocks (attached) so I'm confident the suspension should cycle properly. But a final real test would be nice.

 

[PhillipM]

Would you give some insight? What if I depressurise and drain them to do the build and then have them professionally set?

Filling and bleeding them is the biggest PITA part of assembling a damper - don't drain them if you don't need to. If you've already cycled the suspension with dummy dampers I don't see why you'd need to mess around?
I know you say have them professionally refilled but most places will charge you 50-90 quid per damper just for that...
If you just drop the gas pressure a little, then refill it (with proper fill kit and no loss chucks) then you'll be fine but do NOT empty them and drain any oil out - otherwise they'll need opening up to set the oil levels correctly.

 

[Shox Dr]

Would you give some insight? What if I depressurise and drain them to do the build and then have them professionally set?

To initially test the suspension I made these fake mock up shocks (attached) so I'm confident the suspension should cycle properly. But a final real test would be nice.

View attachment 410067

What @PhillipM says

With respect, you dont know what you are doing, it could cause injury. You dont have to tools, or the knowledge to strip or rebuild them. A rebuild will cost you at least 100quid a damper, even if you *just* let the air out.

 

[rcx132]

What @PhillipM says

With respect, you dont know what you are doing, it could cause injury. You dont have to tools, or the knowledge to strip or rebuild them. A rebuild will cost you at least 100quid a damper, even if you *just* let the air out.

I appreciate your insight into the complexities and risks, that's why I'm asking, to understand my options.

At the moment I'm hearing that small adjustments with the right equipment (eg no loss chuck) might be an option. As it's my first serious buggy build, I'm having to do it in iterations, which might make it expensive to keep going back to a pro.

This is also a knowledge sharing forum whose members are routinely managing to do things that the general public would be advised not to. It's ok to ask. Equipment can be bought or borrowed, skills are learnt.

 

[PhillipM]

I mean they are designed to be user adjustable with pressure changes, just don't drain them down far and definately make sure you don't lose any oil, they're only emulsions so you could lose some if you don't have the schrader at the top or you drop the pressure too far down, make sure you've read through the info to know exactly what you're doing first.

 

[PhillipM]

I will say another thing, if you bought them specced for the car - why do are they not sitting at the correct height? The oil level/gas chamber sizing should have been set with the right spring rate and the gas pressure for the preload to suit the car from the start - or do you not have any weight in the car yet?

 

[rcx132]

I will say another thing, if you bought them specced for the car - why do are they not sitting at the correct height? The oil level/gas chamber sizing should have been set with the right spring rate and the gas pressure for the preload to suit the car from the start - or do you not have any weight in the car yet?

I didn't even know it's possible to buy them specced for the car. I'd been mislead by an article by a popular Pirate4x4 navy engineer who'd written up how he adjusted oil levels and recharged his shocks himself, so I thought I'd be initially doing the same, at least just to the get the car moving. My brother, who's worked on MTB shocks, lent me Nitrogen filling equipment. Until this morning it all sounded fairly simple until I read another source warning about cavitation and other issues I didn't know about.

As far as shocks go, I worked out the travel, checked it cycles, obviously set all the suspension and driveline geometry and clearances, and checked that the shocks would handle the estimated weight.

 

[PhillipM]

I mean you can so long as you know what you're doing with them, the thing with Pirate4x4 is you're generally talking about guys that have been field servicing dampers for years - the reason Fox are so popular is they send out vans and trucks to any sort of decent size event there to revalve and service units there and then and talk people through them.
If you go too low on your initial pressure you'll get cavitation around the main piston, but how much depends on the use, the temperature, the valving stacks, etc. So you need to be aware of all that so you have a rough rule of thumb from experience or work it all out.
Knowing what's in them stock I wouldn't go much below 150psi but it really depends what you're doing, rock crawling it doesn't matter much because the movements are so slow, which is what a huge amount of the info on Pirate 4x4 is aimed at.

 

[Morrisman]

I doubt it's totally relevant to this thread, but I learned long ago that whenever shocks are shipped or stored laid down, you should always cycle them a few times in their final operating orientation, as the damping oil can run around inside and get bubbles trapped in the wrong place.
I found this when I ordered coil overs for my old hot rod, shipped from the US, and once fitted they seemed devoid of any damping. After some research I stripped the springs off, pulled the piston rod in and out a few times, with some erratic resistance, and felt the damping start to work.
Back on the car they were then perfect.

 

[PhillipM]

For some dampers it is, not all, mainly twin tubes, and monotube emulsions a little bit.

 

[roofman]

It's bad enough bleeding a steering damper on a bike, but those bad boys

 

[Shox Dr]

If they are an Emulsion damper, then releasing some but not all the air, to be able to compress the damper fully will not harm it.
If when compressed it does not want to extend under the remaining air pressure. Do not try to pull it apart (extend), slowly add air to allow the damper to extend on its own.

Without knowing the full details of the damper, thats as far I'll comment.

 

[PhillipM]

It's an internal air sprung emulsion damper, hence the big shafts, they use them to have springs and dampers in one unit - unfortunately just means they're a bit poor at both, they suffer with fade/heat and cavitation if you push them - but they're a tidy solution for low speed trails stuff.

 

[rcx132]

It's an internal air sprung emulsion damper, hence the big shafts, they use them to have springs and dampers in one unit - unfortunately just means they're a bit poor at both, they suffer with fade/heat and cavitation if you push them - but they're a tidy solution for low speed trails stuff.

That's it. They aren't great, they also suffer sticksion. Whichever side of the car you get out of, that side will remain lower until the car is moved again. They're compact and used to be low cost, £800 when I first planned my build, but recent economic changes have put the price up to £1300.

 

[PhillipM]

Yea, you can improve that a bit with better oil but it's a consequence of the high pressures needed for the air spring side.

 

[500e]

We re build gas (nitrogen) dampers up to 725psig +-10psig more on bigger machines
You def need the right kit.
If you release gas to fast it aeriates / gasiates the oil then you have a problem, we rebuild totally submerged in oil to stop air entrapment, then remove excess to pre determined level

 

[rcx132]

I called up the dealer and got some advice. He encouraged me to complete my gas kit, saying it's good to be able to set pressure myself with air shocks. He explained how to do it, mainly not to let any oil out, how to purge and equalise pressure, control speed etc. The shocks will have to go back at the end of the build for valving, it's £60 per shock, which seems very reasonable.