- Location
- Billings MT/Rapid City SD
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.Paul S said:
A place for airshox data.
- Thread starter Captain Ron
- Start date
FarmerMatt
NAXJA Forum User
- Location
- Down on the Farm
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.
- Location
- Billings MT/Rapid City SD
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.
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
NAXJA Forum User
- Location
- Down on the Farm
Weasel said:
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
NAXJA Forum User
- Location
- On the horizion
FarmerMatt said:
You must have liked yours more than me. I think I threw mine in the scrap bin.
FarmerMatt said:
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.
--ron
Paul S
NAXJA Member #103
- Location
- Woodland Hills, CA
Paul S said:
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
- Location
- Billings MT/Rapid City SD
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.
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
NAXJA Forum User
- Location
- morganville, nj
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.
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.
- Location
- Billings MT/Rapid City SD
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
NAXJA Forum User
- Location
- On the horizion
Weasel said:
I'm missing something here.
--ron
David Taylor
NAXJA Member #570
- Location
- San Marcos, Ca
Weasel said:
Fox will tell you not to do that.
- Location
- Billings MT/Rapid City SD
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. ??David Taylor said:
- Location
- Billings MT/Rapid City SD
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.Captain Ron said:
- Location
- Port Orchard, WA
thats not right Craig...Weasel said:
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...
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:
- Location
- Billings MT/Rapid City SD
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.
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.
- Location
- Port Orchard, WA
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.
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
then you want to invert the shock, and drain all the oil into a container, and measure the volume -
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....
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.
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 -
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.
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 -
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.
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.
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.
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
then you want to invert the shock, and drain all the oil into a container, and measure the volume -
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....
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.
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 -
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.
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 -
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.
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
NAXJA Forum User
- Location
- morganville, nj
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?
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
NAXJA Forum User
- Location
- morganville, nj
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.
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.
- Location
- Billings MT/Rapid City SD
XJ_ranger said:
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.
- Location
- Port Orchard, WA
Weasel said:
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...
Weasel said:
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
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