A place for airshox data.

[Captain Ron]

Let's see whatcha got.

I'll post pretty pictures in place of real tech.

:D

--ron

[XJ_ranger]

So...

the Fox 2.5 and 2.0 airshocks take a 1/2" bolt which means that you need a 3/4" wrench and a 3/4" socket for the impact...


'its not summer at Liracon unless ive puled a few airshocks!'

[Captain Ron]

Ok, just for the record...

19mm Bryan....

:D

--ron

[Jump This]

My Fox shocks came with an assortment of eye inserts to run metric or standard hardware!
I can go both ways now...:eek:

[Weasel]

If you don't like the unloading Fox has two different pistons for their air shocks. One has bleed holes, use these. Should help quite a bit. Walker Evans air shocks have bleed holes in their standard piston. That why the Walkers handle of-camber better and don't unload as much. Walkers pistons are linear, Fox's are a non-linear, digressive IIRC. Oil Level is easy, add oil till they don't bottom out. N2 pressure controls the ride height. Zip ties around the shock bodies help determine how far your shaft is compressing before bottoming out. Walkers are lighter then the Foxs. In general the rebound has more damping the compression. What else do you want to know?

[Goatman]

Do they work the same at all altitudes?

[Paul S]

The single bleed piston that works so well is actually a Fox Nitro bumpstop piston, not a single bleed shock piston.

Ron, I took my bumps & shocks apart last night & confirmed that my 2" shocks do have bump stop pistons.

From last week I found the following with the 2" rears:
300cc's & ? PSI: worked really well. Very smooth & bottomed only when hit hard.
I added 10cc's & set the PSI to 180 to take out the little bottoming I had. The ride got a little harsh & it bottomed easier.
I added another 10cc's at 180 PSI thinking this would help. Now at 320cc & 180 PSI it bottomed easily on the trail & on the fast & the ride was very harsh.
My conclusion is that the oil controls the dampning, while the Nitro controls the spring rate.
So, I will go back down to 300cc's & increase the PSI to approximately 215, which is what Ron has & is very smooth without bottoming.

Front 2.5's with 440cc's & 210 PSI work great. I don't think they ever bottom, but they are very smooth.
I'm going to take 10cc's out to soften the ride a little bit, we'll see how it goes.

Still don't know which end, if either, I'll need the bumps on.

P

[Captain Ron]

I'll get some piston pics up in a few hours.

--ron

[xDUMPTRUCKx]

thank you guys for doing all the research and spending all the time and nitrogen on getting the numbers that work so people like me can set up air shocks in a day :D

[Dirk Pitt]

Why don't you guys that have them post up your sprung and unsprung weights, front and rear to establish some relativity???

[Paul S]

Why don't you guys that have them post up your sprung and unsprung weights, front and rear to establish some relativity???

I'm new to airs, but from my limited experience I think the most useful tool for anyone is to know what does what. Once you know what does what it's very simple to make changes.
Takes about 1 minute to add Nitro.
About 5 minutes to add oil.
About 20 minutes to reduce oil.
Once we establish what does what, you could bolt 'um on as is from the factory & tune from there.

P

[Captain Ron]

2.5 Piston, double bleed. The bleeds are .093" dia.

http://www.liracon.com/ron/post/asx01.jpg


The bleeds pass though the rebound ports. What looks like 2 additional bleeds are not drilled though, just spotted.

http://www.liracon.com/ron/post/asx02.jpg


This is the single bleed. .065" dia.

http://www.liracon.com/ron/post/asx03.jpg


2.5 piston, compression side.

http://www.liracon.com/ron/post/asx04.jpg


Rebound side.

http://www.liracon.com/ron/post/asx05.jpg


The rebound and compression ports are the same feature size on both pistons. The are the same piston, except for the bleeds. Rebound is a round port...

http://www.liracon.com/ron/post/asx06.jpg


Compression is a significantly larger obround port...

http://www.liracon.com/ron/post/asx07.jpg

http://www.liracon.com/ron/post/asx08.jpg

--ron

[Captain Ron]

2.0 piston, double bleed, .069" dia ports.

http://www.liracon.com/ron/post/asx09.jpg


Single bleed. Same dia.

http://www.liracon.com/ron/post/asx10.jpg


Rebound side.

http://www.liracon.com/ron/post/asx11.jpg


Compression side.

http://www.liracon.com/ron/post/asx12.jpg


Compression port obround feature.

http://www.liracon.com/ron/post/asx13.jpg

http://www.liracon.com/ron/post/asx14.jpg


Rebound port, round feature.

http://www.liracon.com/ron/post/asx15.jpg


2.0 valving specs. The "S" is where they were at from the factory, the arrow is what I ran last week.

http://www.liracon.com/ron/post/asx16.jpg


Same for the 2.5's.

http://www.liracon.com/ron/post/asx17.jpg


Fun with shims. :D

http://www.liracon.com/ron/post/asx18.jpg

--ron

[XJ_ranger]

make sure to have the shock at full extension when adding nitrogen...

and when removing the shock :D
http://www.opiebennett.com/images/Jeep/Shop82307/stp81923.jpg

Fox 2.5 spacers, schrader valve removed to dump all oil and nitrogen -
http://www.opiebennett.com/images/Jeep/Shop82307/stp81924.jpg

pumped out -
http://www.opiebennett.com/images/Jeep/Shop82307/stp81925.jpg

[Paul S]

Just back from 3 days in JV & I think I've got all 4 airs dialed in as good as they'll get, or close to it.

Fronts worked well form the beginning, but I took 10cc's out to soften them up a tad, which worked great. They ride great in all conditions & never bottom.

I took about 25cc's out of the rear & increase the psi by about 40. This puts them at 305cc's & about 220psi. I can't believe the difference this made. They're are silky smooth & only bottomed 3 times in 3 days, & only lightly at that.

P

[Captain Ron]

Just back from 3 days in JV & I think I've got all 4 airs dialed in as good as they'll get, or close to it.

Fronts worked well form the beginning, but I took 10cc's out to soften them up a tad, which worked great. They ride great in all conditions & never bottom.

I took about 25cc's out of the rear & increase the psi by about 40. This puts them at 305cc's & about 220psi. I can't believe the difference this made. They're are silky smooth & only bottomed 3 times in 3 days, & only lightly at that.

P

I hear God only bottomed out 3 times, in the first 6 days, surely you can do better than that.

Without geometric tolerancing, your data is irrelevant.

Please post current info only.

Thanks.

:D

--ron

[Paul S]

I hear God only bottomed out 3 times, in the first 6 days, surely you can do better than that.

Without geometric tolerancing, your data is irrelevant.

Please post current info only.

Thanks.

:D

--ron


Alright smarta$$, ? for ya: now that I've got the spring rate where I want it, how do I change the ride height without screwing everything up?
I've got about 7.5" of rear shaft at ride hight, I want to lower it to a little less than 7", any ideas?

P

[Captain Ron]

Alright smarta$$, ? for ya: now that I've got the spring rate where I want it, how do I change the ride height without screwing everything up?
I've got about 7.5" of rear shaft at ride hight, I want to lower it to a little less than 7", any ideas?

P

This is where I think I was going in the wrong direction the last height adjustment I made. I went down about a half an inch like you want to, added oil, and reduced pressure. I'd been working that trend for a few adjustments, and the front started bottoming.

--ron

[Goatman]

I've never messed with these, but from a total lack of knowledge perspective it would seem that if you removed oil and kept the pressure the same that the ride height would be lower.

Or do you have to mess with both and tune them over again?

[Captain Ron]

You can add or remove pressure for ride height, but it comes with a change in rate.

If it's a small change in pressure, no big deal. The problem is that it's rarely a small change, smaller than 5 psi. 10 psi is alot of change and has a noticable impact.

It's a treadmill. When you gettin on? :D

--ron

[Goatman]

I'm not. :D



I'm liking my coilovers just fine, especially when the air bumps go in the front next week. I'm taking some time to get the valving and spring rates dialed in on the rears, but once it's done it will be done for good. The fronts are great, moving the secondary collar down an inch last weekend helped nicely to keep the bottoming to a minimum and the air bumps will take care of the rest.

[Paul S]

I've never messed with these, but from a total lack of knowledge perspective it would seem that if you removed oil and kept the pressure the same that the ride height would be lower.

Or do you have to mess with both and tune them over again?

That's exactely what I just did. I took out 10cc's & filled back to 220psi. This lowered it about 1/2"
Tradeoff? We'll see...

P

[vetteboy]

You can add or remove pressure for ride height, but it comes with a change in rate.

If it's a small change in pressure, no big deal. The problem is that it's rarely a small change, smaller than 5 psi. 10 psi is alot of change and has a noticable impact.

It's a treadmill. When you gettin on? :D

--ron

So wherever your ride height is, you have a fixed spring rate to go along with it? There's no way to mix & match to tune it to your rig?

Weird.

[Goatman]

So wherever your ride height is, you have a fixed spring rate to go along with it? There's no way to mix & match to tune it to your rig?

Weird.

No, the ride height and spring rate have virtually endless possibilities. I see the guys messing with it all the time. The hard part it seems is that on a C/O you can clearly deal with spring rate, ride height, and shock valving all seperately, and on the air shocks all those are interrelated.

[Weasel]

No, the ride height and spring rate have virtually endless possibilities. I see the guys messing with it all the time. The hard part it seems is that on a C/O you can clearly deal with spring rate, ride height, and shock valving all seperately, and on the air shocks all those are interrelated.


Yep pretty much. But really like vetteboy suggested you are pretty much limited to your spring rates. There is only a certain amount you can do with the oil, and that determines where you shock will bottom or hydrolock.

So for instance on our baja shocks we set them up so they bottom with 1/8"- between the body and end of the shaft. And from there we are pretty much stuck with the spring rate at a certain height. It works well fro us so we havn't had any issues.

You can change oil wieghts but that just plays into the damping.

[Matt S.]

So wherever your ride height is, you have a fixed spring rate to go along with it? There's no way to mix & match to tune it to your rig?

Weird.

the real kicker is that depending on where you are in the travel of the shock, the spring rate progressively changes... even with everything else the same...

PV=nRT...

F=PA...

[Weasel]

the real kicker is that depending on where you are in the travel of the shock, the spring rate progressively changes... even with everything else the same...

PV=nRT...


actually the spring rate is progressive throughout the entire range of travel. And the above equation doesn't apply. It doesn't account for the oil/nitrogen interaction, gasification (not sure if thats the correct term can't think of it right now). I tried a ton of calculations to try and predict the spring rate but no luck. Something funky happens, I suppose it could be figured out but you reach a point that it's not worth the time.

[XJ_ranger]

actually the spring rate is progressive throughout the entire range of travel. And the above equation doesn't apply. It doesn't account for the oil/nitrogen interaction, gasification (not sure if thats the correct term can't think of it right now). I tried a ton of calculations to try and predict the spring rate but no luck. Something funky happens, I suppose it could be figured out but you reach a point that it's not worth the time.

the emulsion technology takes the nirogen away from the ideal gas, but the concept is the same... the equation doesnt work, but the concepts are good...

more good airshock data here:
http://pirate4x4.com/tech/billavista/PR-Airshox/index.html

AndI accidently posted as SCRAPPY AGAIN above... stupid shared computers... :confused1

[Weasel]

the emulsion technology takes the nirogen away from the ideal gas, but the concept is the same... the equation doesnt work, but the concepts are good...

more good airshock data here:
http://pirate4x4.com/tech/billavista/PR-Airshox/index.html

AndI accidently posted as SCRAPPY AGAIN above... stupid shared computers... :confused1

Emulsion, that what I was looking for.

[vetteboy]

So aside from weight. (edit: and price)

What advantages are there to running airshox vs. coilovers? Doesn't seem like simplicity is one of them, but I don't know much about them.

I've driven maybe 4-5 airshox rigs, and I've not driven one that I liked better than comparable coilovered rigs. But I can't say for sure that the airshox ones were set up 'properly' either.

[Captain Ron]

...
PV=nRT...


As you already know, this does not account for emulsification, at a major simplification.

Of course, maybe you have not changed my ratios yet this season.

Wait, that'll be Scrappys job...

:D

--ron

[Paul S]

So aside from weight. (edit: and price)

What advantages are there to running airshox vs. coilovers? Doesn't seem like simplicity is one of them, but I don't know much about them.

I've driven maybe 4-5 airshox rigs, and I've not driven one that I liked better than comparable coilovered rigs. But I can't say for sure that the airshox ones were set up 'properly' either.

I don't think there are any advantages, even the cost is within $100 when you go to 2.5's. But, there's just something about 'um.
I was100% set on F/R coilovers for my Summer remodel, but after driving Matt's car half way up Jack & driving Ron's car through the desert & up/down part of Resolution I couldn't get it out of my head how much I liked the feel.
I don't have the experience with coilovers to know whether or not you can get the same kind of feel, I just really like the smooth, progressive feel of airs.
I think it's definitely a little more tricky setting them up though, as with the wrong pistons, oil level, etc., they're terrible, while coilovers work alright with things not perfect.

Paul

[Weasel]

So aside from weight. (edit: and price)

What advantages are there to running airshox vs. coilovers? Doesn't seem like simplicity is one of them, but I don't know much about them.

I've driven maybe 4-5 airshox rigs, and I've not driven one that I liked better than comparable coilovered rigs. But I can't say for sure that the airshox ones were set up 'properly' either. Depends on the brand, which have you ridden with? I know from talking with Jason Paule that the Walker Air shocks seem to ride/work better then the Fox air shocks. I would say it's due to the bleed holes that are in the Walker pistons.

Piston design is going to be what makes the largest difference. The walkers are a linear with bleed holes. Fox's tend to be a progressive, bleed holes are not standard but you can get them. They also have digressive pistons which i don't think you would want. For the difference between the two, airshocks are pretty simple. You put oil in them till they bottom where you want and the air them up to the ride height you want. Coilovers are the best as far a tune-ability. You can change ride height, spring rate and progressive pretty independently of each other.

The biggest pro for airshocks is weight. The biggest con would probably be keeping them cool and tune-ability. For fast stuff and large bumps they will probably start fading depending on the weight of the rig. Jason's comp buggy doesn't take the huge jumps and hits as well as the rock race buggy with C/O.

And valving is just valving. It's tricky no matter what kind of shock it's in.

[vetteboy]

Mostly Fox. I don't think I've driven any Walkers.

Coilover experience is both Fox and Racerunner for the most part.

Not so much interested in the differences as the advantages. What will an airshock do for me that a coilover with equivalent spring rate won't? Assuming at least a dual-rate coilover, more than likely a dual rate with a tender as that's what I'd run.

I've crawled a few airshock rigs that really had issues with going back to neutral after being flexed out, or off-camber. Like I'd come off a large boulder on one side and the rig really didn't want to balance like it would with a regular coil spring setup. Is this a problem with airshocks in general, or just one that didn't dial in the spring rate properly?

[Weasel]

Thats probably a problem with the piston. One of the reasons most guys run a sway bar with them to provide some force to get the fluid flowing back through the piston.

The way to fix this without using a sway bar is to get a piston with bleed holes or drill them in the piston it's self. That why the walkers do better with the off camber as they have the bleed hole.

Bleed holes will allow fluid flow through the piston. You could also include a bleed disc which would be installing a disc slightly smaller then the largest disc on the bottom of the stack. This will also allow fluid to flow accrossed the piston in low velocity situations but will effect high speed vavling charcteristics. The bleed holes will "choke off" at a certain velocity allowing the valve stack to due the work.

I don't know really what a air shock will give you over a coilover except for weight savings. I guess if you don't want to mess with spring rates, but you do need to make sure the air shock is rated for the weight of the vehicle.

[Paul S]

Depends on the brand, which have you ridden with? I know from talking with Jason Paule that the Walker Air shocks seem to ride/work better then the Fox air shocks. I would say it's due to the bleed holes that are in the Walker pistons.

Piston design is going to be what makes the largest difference. The walkers are a linear with bleed holes. Fox's tend to be a progressive, bleed holes are not standard but you can get them. They also have digressive pistons which i don't think you would want. For the difference between the two, airshocks are pretty simple. You put oil in them till they bottom where you want and the air them up to the ride height you want. Coilovers are the best as far a tune-ability. You can change ride height, spring rate and progressive pretty independently of each other.

The biggest pro for airshocks is weight. The biggest con would probably be keeping them cool and tune-ability. For fast stuff and large bumps they will probably start fading depending on the weight of the rig. Jason's comp buggy doesn't take the huge jumps and hits as well as the rock race buggy with C/O.

And valving is just valving. It's tricky no matter what kind of shock it's in.

Go back & read page 1. Fox's do come with bleed holes, 2 of 'um. The key to making Fox's work is throwing the standard 2 bleed hole pistons in the trash & replacing them with the single bleed hole 'bumpstop' pistons. I can't even describe how much difference this makes.

Paul

[Paul S]

Mostly Fox. I don't think I've driven any Walkers.

Coilover experience is both Fox and Racerunner for the most part.

Not so much interested in the differences as the advantages. What will an airshock do for me that a coilover with equivalent spring rate won't? Assuming at least a dual-rate coilover, more than likely a dual rate with a tender as that's what I'd run.

I've crawled a few airshock rigs that really had issues with going back to neutral after being flexed out, or off-camber. Like I'd come off a large boulder on one side and the rig really didn't want to balance like it would with a regular coil spring setup. Is this a problem with airshocks in general, or just one that didn't dial in the spring rate properly?

Sounds like a valving issue, as I've never noticed that with Mine, Matt's, Ron's, Rick's or Dave's car.
There is however enough stiction that if you push down / pull up on a corner it will stay there.

BTW, non of us run sway bars. Matt & Ron both ran sway bars for awhile, but took them off & prefer it without.
I fully planned on putting one, as I'm more of the pro swaybar, anti big travel type, but it's so stable there's absolutly no need. Interestingly, it's much more stable than it was with rear leaves/front coils.

Paul

[Weasel]

Go back & read page 1. Fox's do come with bleed holes, 2 of 'um. The key to making Fox's work is throwing the standard 2 bleed hole pistons in the trash & replacing them with the single bleed hole 'bumpstop' pistons. I can't even describe how much difference this makes.

Paul But they are not standard with air shocks. You have to buy the piston. Walkers come with the shocks.

[Weasel]

There is however enough stiction that if you push down / pull up on a corner it will stay there.

BTW, non of us run sway bars. Matt & Ron both ran sway bars for awhile, but took them off & prefer it without.
I fully planned on putting one, as I'm more of the pro swaybar, anti big travel type, but it's so stable there's absolutly no need. Interestingly, it's much more stable than it was with rear leaves/front coils.

Paul Sounds like you have your pretty well tuned then.

[Paul S]

But they are not standard with air shocks. You have to buy the piston. Walkers come with the shocks.

The 2 hole piston is standard with Fox.
I ordered the single bleeds seperatly.
Dave ordered his shocks with the single bleeds & they screwed-up & sent him the dual bleeds. He called Fox directly to straighten it out & was told that they had never built them with singles, but it was not a problem for them to do it for him.

Paul

[Weasel]

The 2 hole piston is standard with Fox.
I ordered the single bleeds seperatly.
Dave ordered his shocks with the single bleeds & they screwed-up & sent him the dual bleeds. He called Fox directly to straighten it out & was told that they had never built them with singles, but it was not a problem for them to do it for him.

Paul Hmm, didn't know that. Wonder if that is something that has changed recently cause I was told that they didn't come with the typical air shock, but that was sometime ago.

[FarmerMatt]

I know nothing about tuning these things & don't really want to, but here's my experience with them. I run Rock Equipment air shocks all the way around & they came setup nicely. I've never had them apart & never added or subtracted oil. They do not bottom out & I can drive as fast as my 6 squirrels will allow through the desert. I had to swap out one front for a shock that I bought from Poly Performance. It was supposed to be their super secret special "rock crawler" valving. That thing was more wishy washy than an earth worm. I swapped it back out as soon as I could...What paul says is true. My rig is more stable than it ever was on traditional springs & whoops are a blast to drive through. The sway bar is now garage art sitting on the shelf.

[Weasel]

Were the Poly shocks air? Usually they have good stuff.

Half of shock tuning is really driver preference as well. What feels washy to you someone else may love.

I planning on going to air shocks on my XJ.

[FarmerMatt]

Were the Poly shocks air? Usually they have good stuff.

Half of shock tuning is really driver preference as well. What feels washy to you someone else may love.

I planning on going to air shocks on my XJ.

Poly doesn't build their own. They just valve them to the application. I believe it was a Fox, but it also could have been a swayaway. Both are good shocks, but just weren't setup anywhere close to where I think they should have been. Personal preference does play into it some what, but I think most agree on the general ball park. If I was playing baseball @ Dodger Stadium than these shocks were playing Soccer in Pakistan... They would bottom out driving over a pot hole. The appeal of the air shock is supposed to be it's simplisity of setup & use, but that seems to be proving itself false with the problems many are complaining about. I've been happy because I haven't had to worry about the setup. I air them up & go. I've had 2 problems since getting the Rock Equipment shocks. The first was that the shafts started pitting from the rocks getting thrown at the rear shocks from the front wheels. The pitting slowly took out the seals. The second was a blown seal which I believe is because I'm just too heavy in the front for 2" airs (I had the fronts aired up to 380#...). I'm now running 2.5" shocks all the way around along with shock boots to help protect the shafts. With the 2.5's I'm running 240# in the fronts & 185# in the rears & they feel great. There is absolutly nothing like seeing a long series of whoops in front of you & standing on the skinny pedal...

[Captain Ron]

...
The sway bar is now garage art sitting on the shelf.

You must have liked yours more than me. I think I threw mine in the scrap bin. :D

...
The first was that the shafts started pitting from the rocks getting thrown at the rear shocks from the front wheels. The pitting slowly took out the seals.
...

I have a shot you'd be interested in seeing. I was going to show you in November what I think the difference in shock makes are... the pistons, seals, sealing system. My rear 14's have been on for almost 2 years now. Looked it up,well over 25 runs out there. The lower third of the shafts are in atrocious shape, Deep pitts, but no leaks yet. If you remember, I ran the 2.0's in front initially 16's. Beat the hell otta them. I was just looking at them yesterday, they also have major pitting after around 10-15 runs, but, they never blew or leaked.

I just finished blueprinting the pistons. Wire EDM, not just for shafts anymore. Valve shims? That's what God made a punch press for. :D

--ron

[Paul S]

That's exactely what I just did. I took out 10cc's & filled back to 220psi. This lowered it about 1/2"
Tradeoff? We'll see...

P

Well, this didn't work. Bottomed easily on the trail & in the fast. Amazing that 10cc's could make such a difference.
This knida shoots down my notion that more PSI increases the springrate, & confirms what Ron said a few months ago, which in a nutshell was that more/less oil/PSI can increase/decrese springrate in any combination, depending on the combination. At least I think that's what Ron said:doh:
I guess these things really are infinately adjustable & tunable, but someone needs to come out with a tuning airs for dummies book.

Paul

[Weasel]

When you say bottoming do you mean when the shaft contacts the body are how easily the shock will compress, shaft rate?

I'll have to reread this thread when i get home but there is not alot you can do with the oil. All it does is provide a media for the vavling to work. There is a minimum level of oil need to hydrolock the shock at the end of it's travel. If you have more oil then the shock will hydrolock or bottom sooner in its' travel. If you run less then the minmum level of oil then you get some wierd behavior were the piston will be traveling through the gas an oil. At this point you would be relying on the very high spring rate (infinate) to keep the shock from bottoming. I don't know for sure but I would think that this would not be an effective dampening method.

To set them up fill with oil till the shock bottoms out right at full compression or 1/4" before and then add gas until you get your desired ride height or travel ratio.

If you are doing it the other way then I can't even begin to think how to explain whats going on. We did alot of testing different setups when first getting our baja air shocks and never did figure any relationships or good setups out and yes small changes in oil made large differences. We now use the method above with good results.

[vetteboy]

I will add this...two weekends ago I had an opportunity to bomb around in a buddy's rig, with 2.5" airshocks up front and regular coils in the rear.

I'm much more impressed with the 2.5s. I guess everything else I've tried so far had been 2". The 2.5s had a pretty neat balance between stiffness and compliance, and even without any additional air bumps they never bottomed.

I'm back to reconsidering them for the front of my rig, I may still just try some air bumps first. Lots less reconstruction if I go that route as I'm already happy with my spring rate up there.

[Weasel]

I've seen quite a few rigs with front air shocks and rear coilovers or coils, why not run them all the way around or on the rear and the others on the front?

[Captain Ron]

...
To set them up fill with oil till the shock bottoms out right at full compression or 1/4" before and then add gas until you get your desired ride height or travel ratio.
...

I'm missing something here.

--ron

[David Taylor]

To set them up fill with oil till the shock bottoms out right at full compression or 1/4" before and then add gas until you get your desired ride height or travel ratio.



Fox will tell you not to do that.

[Weasel]

Fox will tell you not to do that. What does Fox recommend. Thats what I have been told by Randy at Walker Evans and that is how Fox told Twisted Customs to set theirs up. ??

[Weasel]

I'm missing something here.

--ron Another way at looking at it would be fill the shock full of oil and no gas, open the valve and compress the shock until there is 1/4"-1/8" shaft showing. Then measure the oil left.

[XJ_ranger]

When you say bottoming do you mean when the shaft contacts the body are how easily the shock will compress, shaft rate?

I'll have to reread this thread when i get home but there is not alot you can do with the oil. All it does is provide a media for the vavling to work. There is a minimum level of oil need to hydrolock the shock at the end of it's travel. If you have more oil then the shock will hydrolock or bottom sooner in its' travel. If you run less then the minmum level of oil then you get some wierd behavior were the piston will be traveling through the gas an oil. At this point you would be relying on the very high spring rate (infinate) to keep the shock from bottoming. I don't know for sure but I would think that this would not be an effective dampening method.

To set them up fill with oil till the shock bottoms out right at full compression or 1/4" before and then add gas until you get your desired ride height or travel ratio.

If you are doing it the other way then I can't even begin to think how to explain whats going on. We did alot of testing different setups when first getting our baja air shocks and never did figure any relationships or good setups out and yes small changes in oil made large differences. We now use the method above with good results.
thats not right Craig...

The more oil you have, the less volume of N2 at the same ride height - right?

nitrogen being the compressable thing in the shock, the more you have, the more 'compressable' the shock is, the lower the spring rate, the better chance of bottoming at the same speed... etc...

the more oil you have, the less n2 you have at the same ride height, the higher the spring rate...

section view of an airshock...
http://www.pirate4x4.com/tech/billavista/PR-Airshox/%21%20internal%20small.jpghttp://www.pirate4x4.com/tech/billavista/PR-Airshox/!%20internal%20small.jpg (http://www.pirate4x4.com/tech/billavista/PR-Airshox/%21%20internal%20small.jpg)

of course a change in valving can effect the feel more than a change in spring rate, but you cant 'valve out' bottoming...

what valving did you run in your airshocks for the Baja? factory Fox valving for the 2.0 is WAY tooo stiff for baja weights... we found that last year, but didnt have time to fawk with it and got beat to shit in the endurance race :shiver:

[Weasel]

Yeah thats right. But there is a point at which you do not have enough oil for the piston to travel in. I will have to look at our shock specs but I thought there was a minimum oil level. Above that you can mix and match oil and pressures all you want for which ever combination you like. Everyone already knows this. We played with amounts below the recommended oil levels and got pretty odd ride characteristics. Not recommended, which is what I though Paul had.

For some reason I got it my head that Paul was running below that level but rereading I don't think that is the case.

To find our levels we started at the oil level walker gave us and worked downwards 10cc's at a time adjusting the N2 to get the desired ride height and then testing it. Once we reached a point were we felt the ride was diminishing then we reduce it 20cc more to be sure there the ride was decreasing, then went back to the first decrease value and increased by 5cc. And this was done with the lightest driver for the following reasons.

We run the same amount of oil for every driver but we vary the amount of gas so the car will sit at the correct ride height given the weight increase/loss. But it does not matter what the N2 level is the shock will bottom at the same point regardless. This works very well as we can adjust the spring rate per event and driver without worrying about damaging the shocks without changing the oil level. But thinking about it with a rig you probably are not adjusting the pressure as much as we do. So your oil level would not be as critical as you can rely on the extra spring rate to keep the shock from fully bottoming.

What I wrote above is what has been suggested to me to do. And should give you the minimum oil level you can run, which I don't think is the issue. However if you want to get a starting point that would be it and work your way up trying increasingly oil levels and varying psi's.

I valved all our shocks. We run Walkers and they came with a flutter shim stack that took out right away. I can take see if I can find a picture of them as I don't remember exactly what the shims were. Against the face of the piston on the compression side I placed a shim one size smaller then the largest to create a bleed shim of sorts. This year I will be eliminating it and drilling another bleed hole.

[XJ_ranger]

This is all based on Mini Baja junk, but the process is the same.

So after you spend all the time making your link suspension work, and making the tabs and mount your air shocks, and cycle the suspension, making sure the suspension doesn't bind, Take it out for a spin, and see what you think you need to do.
Keeping in mind that nitrogen is compressible, and oil is not. More oil = stiffer spring rate, less oil = softer spring rate. there is a recommended oil level for each different shock, Polyperformance lists these for Fox Air Shocks on their web page here:
http://polyperformance.com/shop/Fox-2.0-Air-Shocks-p-102.html

We are tuning 8.5" travel 2.0 Airs -

Part Number: 980-99-016-A Travel: 8.5 A/S Extended: 24.09 Collapsed:15.59 8.5 Oil Level: 200 cc Price:$225.00

This is the oil level they come from the factory with, and the recommended oil level.

Knowing this will allow you to tune - either adding oil or subtracting it to match your needs. Start with large, drastic changes (20-30cc's of oil level) and then you get a ball park, rather than making 5cc changes right away. 5cc's makes a large difference in the feel of the shocks, and generally I end up tuning to about the 2cc amount. Adding oil is MUCH easier than subtracting.

Oil is set to determine the spring rate, nitrogen is set to provide the ride height.

any way, we installed ours, and drove them, and felt that the front end was WAY too stiff, so we knew that we needed to take oil out.



http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82898.jpg

after jacking the vehicle up, and taking all the weight off the air shock, bleed the nitrogen out - the schrader valve works well... Draining quickly can cause the shock to burp oil, draining slowly keeps the oil in the shock
http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82899.jpg

then you want to invert the shock, and drain all the oil into a container, and measure the volume -
http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82901.jpg

This allows you to verify the number listed on PolyPerformance, and gives you a baseline to compare too.

slowly depressing the shock makes the shock oil come out....
http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82902.jpg

after you've got most all the oil out, and measured, pull the whole shcrader valve off, and clean the whole area - this will make adding oil easier.

To determine the MAXIMUM amount of oil your shock can take, compress the shock all the way, fill with oil till it wont take anymore, then dump it out, and measure the volume. Any more oil than this, and your shock wont have full travel, and will hydro lock. This will also be the stiffest spring rate you can run... (keeping in mind that the spring rate is not linear, but progressive through the travel)

I have approx 215CC's of oil here (measured in a graduated cylinder later) and guessed that I burped out and lost to the floor from overzellous shock compressing about 5cc's more, so 220cc's.
http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82906.jpg

Knowing that I needed less, I got new, clean shock oil, poured our 180cc's into a beaker, and used a syringe to insert the oil into the shock.
I used the graduations on the syringe to verify my amounts -
http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82908.jpg

http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82909.jpg

http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82911.jpg

after getting all the oil into the shocks, put the valve back on, put the shock back in the vehicle, (still fully extended), and get your nitrogen source ready.
http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82912.jpg

We found our Nitrogen regulator to stop getting higher pressure at 150psi, so note that regulator selection is important - High pressure regulators are required for the 0-550? psi range the shock can take. Also expect to be doing this MANY times, so buying a Nitrogen kit from Poly Performance isn't a bad idea...

Select the amount of nitrogen to put into your shocks - kinda arbitrary in the beginning, but after a short while, you'll get good a guessing.

We use a Fox Shock charging tool with a built in gauge -
http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82918.jpg

This screws onto the outside of the schrader valve and allows the user to 'overcharge' the shocks, then finely bleed down the pressure to the desired pressure.

NOTE: always charge shocks at full extension with no load on them -any other way will give you bad readings, and you wont be able to baseline the number...

Charge the shock, then put the weight of the vehicle on it, jump up and down, shake the rig around, then look at it. Measure your ride height. More nitrogen will make it higher, less will make it lower. Jack it back up, and add or remove as necessary...

Then repeat on the other side.

http://www.opiebennett.com/MiniBaja/CSUSMiniBaja51408/stp82919.jpg

Re check that all your bolts are tight, that your limit straps are bolted tight, go for a spin around the driveway, up the block and back. Hit a curb at speed, crawl up your trailer, then pull back into the garage, tear it all down, and re-do it till you get an acceptable spring rate....

very much an iterative process.

[vetteboy]

Nice tech Opie.

Car's looking pretty cool too, I miss doing that stuff (been out of it since '05).

Our team that year was the first at our school to use air shocks instead of coilovers. IIRC we used the same Fox ones you've got. We didn't have a damn clue how to tune them, so we basically bolted them in and ran it. It did OK but I never liked them as much as the coilover setup we ran the previous years. Somewhere I've got a jump video of a perfect front cartwheel in the air because the rear just liked to rebound up and over everything.

In MiniBaja East we never had the rock crawling either, we just had to make the damn thing float. :(

What's your front center section from?

[vetteboy]

Actually, they've still got the video on the server from '05.

http://www.tcnj.edu/~minibaja/baja2005/baja2005lo.wmv

There's some decent footage of how the car handled with the airshocks as received, and the last 3rd of the video shows how bad the rear rebound situation was. Real bad.

edit: 2:58 is where the fun stuff happens.

In retrospect, after watching that video again, it's not surprising that we smoked the CVT at the east comp that year.

[Weasel]

Keeping in mind that nitrogen is compressible, and oil is not.
Oil is set to determine the spring rate, nitrogen is set to provide the ride height.



:confused: The nitrogen is the spring rate? You can run less nitro with the same amount of oil and your static spring rate will change. If you run less oil then what the shock will take at ful compression what is your piston going to travel through and give you damping? Piston won't work in nitrogen, I don't think, so it would seem you would loose damping at some point in your travel.

[XJ_ranger]

:confused: The nitrogen is the spring rate? You can run less nitro with the same amount of oil and your static spring rate will change.

Changing the nitrogen level while keeping the same oil level will drop the ride height, and yes - change the spring rate - but generally when ive been tuning these, we've wanted a specific ride height, and had to tune to that... so more oil, less nitrogen = same ride height as less oil, more nitrogen... BUT! this isnt linear - note that Paul S earlier mentioned adding 10cc's and dropping the pis by some, and had unexpected results - this isnt going to be a set it once and its perfect the first time thing - the problem with suspension tuneing, is that its all based on driver preference... what I think feels great, might feel WAY too stiff for you...

If you run less oil then what the shock will take at ful compression what is your piston going to travel through and give you damping? Piston won't work in nitrogen, I don't think, so it would seem you would loose damping at some point in your travel.

that kinda makes sense, but kinda doesnt...

I know that the AS that I posted about had 220cc's of oil in them, and they got to full compression with that ammount of oil in there...

The reccomended oil level for a 8.5" travel A/S (according to Poly) is 200cc... and that is supposedly what Fox ships them with...

I doubt that fox would ship an airshock without enough oil in it to have valving through the enture travel...

thoughts?

from here:
http://www.pirate4x4.com/tech/billavista/PR-Airshox/index.html

http://img241.imageshack.us/img241/1112/internalmediumjp7.jpg
http://www.pirate4x4.com/tech/billavista/PR-Airshox/%21%20internal%20medium.jpg

[Weasel]

We run the Walkers and tune by driving and also by a shock dyno we built and yeah you can't really spreadsheet it. Have to tune by driver and everyone like something different.

Early when we started using these AS (three years ago) we tried running low oil levels and more nitrogen and had some odd shock behavior due to what we guessed is that there was not enough oil for the piston to travel in.

As shown above in the picture, that oil level would seem to be the minimum you would want to run, less and would your damping suffer at some point?

No I doubt Fox would ship with no enough oil.

[Weasel]

I bet the shock body is longer the the shaft travel, allowing some room at the top of the shaft at full compression that you can vary the oil/N amounts?

That would keep your piston in the oil medium throughout the travel.

[XJ_ranger]

I bet the shock body is longer the the shaft travel, allowing some room at the top of the shaft at full compression that you can vary the oil/N amounts?

That would keep your piston in the oil medium throughout the travel.

Id put money on that...

ive noticed 'weird' behavior from the shocks at anything over about 220psi? - but that was back when Ron was running Fox 2.0's in the front of the MJuggy...
I dont remember the exact pressure we started noticing the differences, but the Airs like to be at 'lower' pressures...

[Weasel]

And the relationship between the spring rate and oil level might be linear but I'd bet the rate of change is pretty large as you only have probably 1" to vary the oil/N levels, so 10cc would give a fairly large change. We don't come close to running those kinds of pressures in the baja rig.

[Paul S]

Well, it's been just over 1 year since I first went to airs & I've finally get 'um figured out.
In the end I did a 180 from everything I had been trying to make work.

I found that the single bleed piston in the rear (at least in my light weight car) simply couldn't flow enough oil fast enough & therefore didn't allow me to run enough oil. On my last run of last season I tried duel bleed hole pistons
with much more oil & it worked much better, but by then I was totally burnt on tuning the 2.0's.

I switched to 2.5's in the back. I first tried them with near stock oil & single bleed 'shock' pistons (as opposed to the single bleed bump stop pistons that I run up front). This was way too harsh. I switchwed them out for duel bleed pistons & it smoothed right out.
The benchmark to meet in our group was Dave's rear coilovers with air bumps & mine is now equally smooth/fast.

The front 2.5's have been great since day 1, but I figured out how to make them substantially better this weekend. Dave's going to do the same with his, but since he's running the KOH LCQ, he might want to keep this little mod underwraps for now:shhh:

Paul