S212 Airmatic Calibration?
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2011 E350 Sport Wagon
S212 Airmatic Calibration?
Just had the rear air springs replaced by a local independant on the rear of my 2011 E350 4S wagon due to a leak. Doesn't leak anymore, but it's riding about an inch higher than than it had been and is quite a bit stiffer (talking Honda Fit territory in terms of ride quality). Is there a calibration routine that needs to be run on these simplified SLS systems on the wagons like on the full Airmatic?
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2010 E550, 273 Engine: 2012 S550, 278 Engine
Just had the rear air springs replaced by a local independant on the rear of my 2011 E350 4S wagon due to a leak. Doesn't leak anymore, but it's riding about an inch higher than than it had been and is quite a bit stiffer (talking Honda Fit territory in terms of ride quality). Is there a calibration routine that needs to be run on these simplified SLS systems on the wagons like on the full Airmatic?
What comes to calibration, you don't need one unless you replace level sensor(s). The Airmatic spring system does not care what is lifting the car up. Level sensors tells it where it is and controls air in the springs accordingly..
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2011 E350 Sport Wagon
Ride being an inch higher and feeling stiffer does not make sense other than the height is so high it pulled the shocks all out. Adding right height to air springs makes them softer unless the springs push against a stop, i.e. against fully extended shock or other mechanical limitation. My car easily extends an inch past normal height without bottoming out in the shocks so I really don't understand why it would feel harder unless the car is way higher than normal bottoming out the shocks.
What comes to calibration, you don't need one unless you replace level sensor(s). The Airmatic spring system does not care what is lifting the car up. Level sensors tells it where it is and controls air in the springs accordingly..
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Hmmm.... Your answer confused me on this issue. The increased ride height is the result of increased air pressure in the spring. Assuming the spring is obeying the laws of physics, this additional air pressure by definition makes the spring stiffer and more resistant to deformation or it wouldn't increase the height of the car. You don't have to fully extend the shocks to notice this in the ride quality.
This was spot on and didn't need to be calibrated. Turns out that one of the two ride height sensors had frozen -- perhaps getting jammed when they were yanking on the strut trying to remove the spring. This left the ride height on the driver's side just under two inches higher on the driver's side and about 3/4" higher on the passenger side. Surprising to me was that this didn't break the links. The shop was able to unfreeze the sensor without replacing it and it's back to normal ride height and ride quality now. It'll probably return to haunt me later and I'll end up replacing one or both sensors, but it's working again for now. Thanks for the help!
This was spot on and didn't need to be calibrated. Turns out that one of the two ride height sensors had frozen -- perhaps getting jammed when they were yanking on the strut trying to remove the spring. This left the ride height on the driver's side just under two inches higher on the driver's side and about 3/4" higher on the passenger side. Surprising to me was that this didn't break the links. The shop was able to unfreeze the sensor without replacing it and it's back to normal ride height and ride quality now. It'll probably return to haunt me later and I'll end up replacing one or both sensors, but it's working again for now. Thanks for the help!
Normal coil spring also gets more load from more weight in the car and for this reason car goes down some. Beauty if the Airmatic system is that it adds air in springs to keep the car at set height but adding air does not increase pressure as the needed pressure is the result of the weight of the car.
As I explained in my post earlier the spring pressure would increase if the travel of the shocks would bottom out. In this case car would not be able to raise any further no matter how much pressure is present in the spring.
In short, as long as there is nothing mechanical holding the car down the amount of air pressure in each air spring results from the weight of the car. The springs are in place to carry the car, not forces against mechanical stops (shocks) that limit the upward movement of the car.
Last edited by Arrie; Dec 11, 2021 at 02:10 PM.
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2011 E350 Sport Wagon
The vehicle's ride height is determined by the resistance to deformation of the spring against the load applied. Doesn't matter if it's a steel spring or an air spring. In a steel spring that's largely determined by the mass of the material in the spring and a heavier steel spring will result in a stiffer ride due to that increased resistance to deformation. The air spring is nothing more than a balloon and a balloon's resistance to deformation is largely determined by the pressure in the balloon pressing against the material of the envelope of the balloon and that material's resistance to being deformed by the pressure acting upon it by both the internal air pressure pushing it out and the pressure from the outside trying to collapse it -- in this case, mostly the vehicle weight.
This is something you can easily test for yourself if you wish just using a balloon. It's not magic, it's physics. Believe what you wish, but I assure you that my vehicle is now at the correct height and the ride quality I expect out of it has returned to normal without increasing the weight of the vehicle (the external force). Likewise, the material of the envelope and its resistance to deformation hasn't changed, only the pressure inside of the balloon.
This is something you can easily test for yourself if you wish just using a balloon. It's not magic, it's physics. Believe what you wish, but I assure you that my vehicle is now at the correct height and the ride quality I expect out of it has returned to normal without increasing the weight of the vehicle (the external force). Likewise, the material of the envelope and its resistance to deformation hasn't changed, only the pressure inside of the balloon.
Last edited by maddenma; Dec 11, 2021 at 11:03 AM.
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'11 E350, '11 E550, '98 M3, '95 E320
^ Correct... statically the load is constant, to change ride height requires a change in spring rate, which is achieved with more or less air pressure. Higher (static) ride height = stiffer ride.
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2010 E550, 273 Engine: 2012 S550, 278 Engine
Ride height increase does not increase air pressure inside the spring. It increases volume of air and makes the spring longer as it cannot get any bigger in diameter. Longer air spring gives softer ride as the pressure inside the spring is the same resulting from the weight of the car.
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Ride height increase does not increase air pressure inside the spring. It increases volume of air and makes the spring longer as it cannot get any bigger in diameter. Longer air spring gives softer ride as the pressure inside the spring is the same resulting from the weight of the car.
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And I leave it in here...
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I think the balloon analogy introduces confusion. A balloon has similar resistance to inflation in all directions, but these air spring have different behavior vertically vs diametrally. Vertically it offers zero resistance when sitting on closed shock, car's weight when inflating, or infinity when extended to the maximum allowed by the shocks.
First one is irrelevant since the car shouldn't be driven, the last one offers poor ride when returning from compression since it will hit the shock limits.
The second one, and only useful setting, defines the ride comfort since the pressure in the spring is nearly constant for any height between shocks limits. Any minor increase in pressure, dynamic, like the car coming down is controlled by the bag's elastic resistance itself (ignoring extra plenum/dampers)
My , perhaps incorrect, understanding
First one is irrelevant since the car shouldn't be driven, the last one offers poor ride when returning from compression since it will hit the shock limits.
The second one, and only useful setting, defines the ride comfort since the pressure in the spring is nearly constant for any height between shocks limits. Any minor increase in pressure, dynamic, like the car coming down is controlled by the bag's elastic resistance itself (ignoring extra plenum/dampers)
My , perhaps incorrect, understanding
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2010 E550, 273 Engine: 2012 S550, 278 Engine
I think the balloon analogy introduces confusion. A balloon has similar resistance to inflation in all directions, but these air spring have different behavior vertically vs diametrally. Vertically it offers zero resistance when sitting on closed shock, car's weight when inflating, or infinity when extended to the maximum allowed by the shocks.
First one is irrelevant since the car shouldn't be driven, the last one offers poor ride when returning from compression since it will hit the shock limits.
The second one, and only useful setting, defines the ride comfort since the pressure in the spring is nearly constant for any height between shocks limits. Any minor increase in pressure, dynamic, like the car coming down is controlled by the bag's elastic resistance itself (ignoring extra plenum/dampers)
My , perhaps incorrect, understanding
First one is irrelevant since the car shouldn't be driven, the last one offers poor ride when returning from compression since it will hit the shock limits.
The second one, and only useful setting, defines the ride comfort since the pressure in the spring is nearly constant for any height between shocks limits. Any minor increase in pressure, dynamic, like the car coming down is controlled by the bag's elastic resistance itself (ignoring extra plenum/dampers)
My , perhaps incorrect, understanding
You are correct. The car floats on the air springs (like any car floats on the coil springs) without hitting the shock limits so the pressure in the air springs comes from the weight of the car. Of course, when the wheel hits a bump and wheel moves up very quickly the pressure in the spring goes up accordingly like when the wheel drops in a pothole pressure goes down for that time of the impact, but without counting for these the spring pressure is the result of the weight of the car regardless of the ride height.
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You obvious;y don't know how the air spring system in our cars is built. The pressure in the springs does not change with ride height, at least not in my car and I think they are all built the same way. Pressure would chanhge if the car would raise so high the shocks would have to hold it down, which would be way higher than the "high" setting is.
And I leave it in here...
And I leave it in here...
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1 - Air in and pressure value increasing and the car still down
2 - Air in and tire start expanding, pressure increasing and the car still down
3 - Air in, the tire continues expanding and the car suddenly start rising
4 - Air in, the car continues rising, and (here is the issue) the pressure remains the same
5 - Air in, car no longer rises, tire shape seems fixed ( still a bit of a bulge, more at the front than the rear for the same pressure), and the pressure starts increasing again until the valve is closed.
There are equivalent steps on the air spring. When the air spring reaches the maximum length of the shocks (tire at the maximum visible final shape), the pressure starts to increase to whatever you want (and the bags supports).
Equivalent exercise is before installing inflate two tires to a fixed pressure, install one in the rear and one in the front. Same pressure, correct? Same bulge when installed? Hope not, otherwise, your car would be missing the transmission+engine unit. Measure with an accurate manometer the tire pressures on both tires. Same as before installation? Nope. Same value for both front and rear? Nope. How much is the difference? Minor, but different. Splitting hairs? Possibly, but the conversation is already there.
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I'm gonna eat my words, pull out SDS and record the pressures in the springs and associated ride height.... your argument would be like the pressure in tires is only a result of the car's weight. Can you put more or less pressure in a tire? Not the best example/visual, but when a tire is severely under-inflated and the sidewall is bulged a bit, one can notice the wheel rise when inflating to proper pressure.
The car floats on the springs and the force of the springs is just the counterforce to the weight of the car on the spring. As long as you don't fill the springs to reach the travel limit of the shocks the pressure in the spring stays at what the weight of the car gives it and nothing more-nothing less.
You are so lost with this it is unreal. Unbelievable indeed.
And for your info - there is no individual pressure sensors for each air spring. Only one in the reservoir.
