School Me on Bagged Cars

OK I bought a 50 Olds that was built 30 years ago. It has a Ride Tea compressor and tank in the truck, and a gauge with 2 needles mounted under the dash. I can raise the front or the rear separately. How do you know at what height to have the car when you align the car. Also after the alignment how do you get it to the correct height so the alignment is correct for hi way driving? If you go by the pressure gauge for height, how do you compensate for extra people in the car? All of this bagged stuff is new to me.

 

Two things. First, dont overinflate the airbags or it will ride like it doesn't have any springs. Experiment and maybe measure.

Second, those older systems like that dont really work that well. Today's systems have individual control valves for each bag. Having two bags controlled by one valve allows air to move from one side to the other. So, when you go around a curve the air in the outside bag isn't trapped and can't load up the bag like a spring would which is what you want. Do some Google searches.

 

Familiarise yourself with Boyle's Law.

Pressure is a function of the car's weight and the effective piston area of the bags. The latter isn't something you can measure directly simply, and it doesn't remain constant over the bag's stroke. It can however be deduced from load and pressure at any given height.

Ride height varies with the amount of gas (air) at a (pretty much) constant pressure. To raise the car you add air to maintain the same pressure. It is only when the bag is completely extended, and pressurised against the tensile elasticity of the bag envelope, that the pressure will rise above that needed to carry the car. That is to be avoided.

Ride height appears to vary with pressure because to have an increased amount of air available it is necessary to increase the pressure in the receiving vessel from which the air is supplied.

Spring rate varies with gas (air) volume, again not with pressure. The greater the volume, the softer the spring rate, and the less pronounced the rising-rate characteristics of the bag. And vice versa. You can always soften a stiff bag by adding a small tank or air vessel between the bag and its control valve. You can't stiffen a bag by any comparable means, so if tunability is an issue it's best to start with the smallest safely viable bag, and then add volume as necessary.

Material hysteresis in the bag envelope becomes negligible, and air has much less internal friction than any form of steel spring, so bags require ample damping. Dampers should be as close as possible to absolutely parallel to airbags (i.e. they should match the bag's stroke or motion as closely as possible) and not in series as with a properly designed hydraulic setup.

Air is a proper spring medium with certain characteristics, of which some can be very useful. It is far more than a way of adjusting ride height. Fixed-height air suspension might be perfectly sensible for some builds.

 

Is there a way to add solenoid valves or something else into my system to fix this problem, without replacing the whole system? Here is a picture of what's in the trunk. I forgot to take a picture of the control panel, but it's an air gauge with 2 needles and a rocker switch on each side of the gauge. One rocker switch controls the front bags, the other the rear bags
.

 

I am considering doing that, but I thought I would drive the car with the bags first. Spring pockets are a little hacked with a cutting torch. Not sure if the stock springs will still work. Almost have to remove the bags to find out.

 

You could add another one of those gauges and switch panels then you have 2 dual gauges and 4 switches. You could then use one switch for each corner along with the corresponding needle in the gauge. Easy and cheap like me!!!

 

^^^^^^^^What SS327 said. That's your least cost option. You'll have to experiment with pressures but generally you would run the same in each front bag and the same in each rear bag.

 

If you don't want to lower it on command, look into a set of mechanical height control valves and install them at each corner. They are found on all air ride big trucks, and because of that fact are generally pretty cheap. Set the valve and linkage to the ride height you want, and the valve will automatically fill or release air from the bags to match the load conditions in the car. You can add a couple of solenoid valves to release the air if you still want to power park at a car show.

You can get away with just one HCV on a solid rear axle, just need a couple of one-way valves installed inline to prevent air from flowing between the bags during cornering.

 

The truck in my avatar is on airbags. Frankly, it is a PITA. When new, it would hold air pressure for a couple of weeks. Five years in, it won't hold air pressure for more than a day, so every time you want to drive it and it has been sitting more than a day you have to wait 5 minutes for the tank to build pressure and get the truck off the ground. The truck's air bags are hard-plumbed in -4AN line. There's a set of springs in a box in the shop ready to install (have to fab a "hat" for the spring I took out for the air bag)

Then there's the ride quality issue. For most coil springs the spring rate is linear. For air bags the spring rate is progressive. My truck's air bag spring rate is less than the factory coil spring at ride height, but at a few inches of travel and the effective spring rate is like 2x the factory coil spring. The result is the truck rides very well with the suspension only has minor bumps to contend with but when it hits a pothole, it is jarring. To control the rapid rise in spring rate, you need a shock with a lot of rebound control adjustment - a shock for a coil spring won't damp well enough in rebound. Good adjustable shocks from QA1 for air bags are about $300 a corner.

The tank/compressor/relief pressure switch shown in your photo are ok, but they are 'entry level' components made to a price point. Higher quality components from Viair, Accuair, SLAM and AirLift are considerably more expensive - you get what you pay for. I can't tell from your photo, but you should be using DOT-approved hose and fittings at a minimum, not for compliance, but because they are much less prone to leak long-term.

A step up from the needle valve air regulation system is a good set of manual air valves from AirJax (https://www.airejax.com/) There's no wires or solenoids - it is all pneumatic - about $300

The best ride-height system is from Accuair, but you need to splash out $2-3K for a setup. Accuair went bankrupt in 2000 and was aquired by Arnott, a reputable air bag/coil over suspension componet manufacturer (I have some Arnott's on my Jag and they work well)

You can experiment with a HCV (height control valve) from Haldex and others, but in my opinion you're just creating a 'science project' to try and get it to work. (there's a couple HCVs in my junk drawer that I've never tried) It will never have the level of control that an ECU in a Accuair system will give you out of the box.

Again, it is just my opinion, but about 99% of the DIY air bag systems were fabricated to 'lay frame' or achieve a 'stance' the owner wanted and there's little regard for reliability, ride quality or safety. They spent a lot of money at the factory getting the coil spring suspension to work and it is very difficult for a DIYer to achieve an acceptable airbag conversion without spending a boat-load of money

 

My truck has a Jag suspension under it. When I installed it I made sure that the desired ride height of the truck was at the factory ride-height of the Jag's suspension. To align it, I set a board under the front cross-member to hold it at the factory ride height while I align it. If I am an inch above or below after I've aligned it, I'm still pretty close to the factory alignment specs. As far as compensating for extra p***engers, it doesn't make much difference to the front air bags and I'll tweak the pressure in the rear bags to level out the truck.

 

The more replies I get for this thread, (which I appreciate) the more I am thinking of replacing the air bags with springs. I will drive it this summer and see how it drives. If it is as bad as I think it will be, next winter it will get springs. Remember, I didn't put the bags in it, I bought it that way.

 

I see you're in Minnesota. This is taken from https://airride.co.uk/air/cold-weather-and-air-suspension-systems-what-you-need-to-know/


"Air suspension systems enhance ride comfort and vehicle adaptability but face challenges in extreme temperatures. In cold weather, moisture can freeze within the system, causing blockages in airlines, valves, and fittings. To prevent this, it's essential to drain the air tank regularly, use airbrake antifreeze, and install water traps or air dryers to remove moisture. Additionally, rubber components like air bags become less elastic in low temperatures, increasing the risk of cracks or brittleness. Utilizing subzero-rated air bags and conducting regular inspections can mitigate these issues. Conversely, hot weather can accelerate rubber degradation and cause compressors to overheat. To address this, ensure proper ventilation for the compressor, inspect rubber components for heat-related damage, and minimize prolonged heat exposure by parking in shaded areas. Regular maintenance and seasonal adjustments are crucial to maintaining the reliability and performance of air suspension systems year-round.

Key Challenges and Solutions
1. Moisture Freezing Inside the System

Condensation is a natural by-product of air compression, but in cold weather, any moisture inside your system can freeze, leading to blockages in airlines, valves, and fittings.

How to Prevent Freezing Issues:

Drain the Air Tank Regularly: Water ac***ulates in the tank over time. Draining it monthly - or more often in humid climates - prevents water buildup that could freeze.
Add Airbrake Antifreeze: Specifically designed for pneumatic systems, airbrake antifreeze can be added to the airlines to prevent freezing in extreme conditions. This is especially important if your vehicle is used in subzero climates.
Install a Water Trap, Dryer, or Cooling Coil: Water traps capture condensation before it enters the airlines, while air dryers actively remove moisture. Cooling coils can also help by condensing and collecting water vapor before it freezes. These are effective upgrades to ensure a dry air supply year-round.

2. Reduced Elasticity of Rubber Components

At low temperatures, rubber becomes less elastic, which can impact the flexibility and performance of air bags.

How to Maintain Rubber Components:

Use Branded, Subzero-Rated Air Bags: Most high-quality branded air bags are rated for temperatures between -30° C and 70° C, making them suitable for year-round use. Choose air bags with these ratings to ensure durability in freezing conditions.
Inspect Regularly for Damage: Check for cracks, hardening, or brittleness in the air bags and hoses. Catching issues early can save you from unexpected failures in extreme weather.

Real-World Examples: Cold Climates and Air Suspension Success

Air suspension systems are not limited to mild climates. Vehicles like Range Rovers and Bentleys, which often come with factory-installed air suspension, are designed to operate in freezing conditions. Additionally, many buses, lorries, motorhomes, and 4x4s use air suspension in cold environments, such as Russia, the Baltic States, and ski resorts.

The key to reliability in these conditions is proper moisture control and quality components. With regular maintenance, freezing issues can be entirely avoided - even in temperatures as low as -30° C."

 

Time to update the management something like Airlift 3p or 3h I daily drive a VW Golf on air ride even in the winter ( just had 20 inches of snow ) and have absolutely no problems ! Align the car at ride height park it on the frame

 

Thanks for the winter update, but the car will never be driven in the winter due to all the salt used on the roads around here. My black daily has white sides on it now due to the salt. Gotta get to the car wash soon.