Lower Self-Level Air Suspension?

[J_Mainie]

Just like the title says, I was wondering if it was possible and if so how? I just bought some Style 63 wheels and wanted to reduce the wheel gap that I had. Thanks in advance.

[4.8isX5]

Do you have just rear bags or do you have 4 corner air equipped and the up/down switch by light switch like so..

[bcredliner]

Short answer is yes. As mentioned, how depends on existing suspension. Spacers will also improve the appearance.

[swell64]

How what's the easiest way with 4 air suspension? Found something in Ebay but its in the UK?? What about here in the states Thanks

[civdiv99]

Change the height calibration through inpa or GT1 or similar.

Set your new fav standard height. Don't get carried away, though.

[swell64]

Originally Posted by civdiv99

Change the height calibration through inpa or GT1 or similar.

Set your new fav standard height. Don't get carried away, though.

THANK you, WILL do some research to see who has those systems here in CHICAGO Area thanks

[J_Mainie]

Originally Posted by 4.8isX5

Do you have just rear bags or do you have 4 corner air equipped and the up/down switch by light switch like so..

I have bags on all 4 corners and the switch but I want it to stay lowered instead of it rising back up.

[civdiv99]

If by stay lowered you mean you want to use your height switch and have it not rise up at applicable speed, I think you are in for a losing battle.

You can set a lower static ride height, by which "normal" can be somewhat lower, and it'll happily do that and still go up and down via your switch (just a net change from that reference point).

You don't want to get real aggressive on that in any case as you can damage your bags going too far into low rider territory and then wailing around. What's safe? Dunno. Wasn't willing to be the guy who learned that first hand.

You will also find your ride characteristics will change, and not n the soft and squishy way. When you run lower, the air volume in the bags is less. When you tag a bump, the suspension compresses and the air volume in the bag decreases. In a lowered status, the amount of that additional decreased volume from the bump is a greater proportion of the static volume than it would be at normal height. The result is an increase in the rising rate compared to normal. You will be able to feel that. That may be ok, just mentioning.

[Helihover]

Originally Posted by civdiv99

If by stay lowered you mean you want to use your height switch and have it not rise up at applicable speed, I think you are in for a losing battle.

You can set a lower static ride height, by which "normal" can be somewhat lower, and it'll happily do that and still go up and down via your switch (just a net change from that reference point).

You don't want to get real aggressive on that in any case as you can damage your bags going too far into low rider territory and then wailing around. What's safe? Dunno. Wasn't willing to be the guy who learned that first hand.

You will also find your ride characteristics will change, and not n the soft and squishy way. When you run lower, the air volume in the bags is less. When you tag a bump, the suspension compresses and the air volume in the bag decreases. In a lowered status, the amount of that additional decreased volume from the bump is a greater proportion of the static volume than it would be at normal height. The result is an increase in the rising rate compared to normal. You will be able to feel that. That may be ok, just mentioning.

Lowering won't ruin the bags. It just puts them in a new posistion. Some older bags (which probaly need replacing anyways) could develop a leak after lowering, due to the new posistion/creases being applied.

The air bags are not shocks, they are springs. Lowering could change your spring rate in therory, but there is still the same amount of air pressure required to hold up the vehiçle. Shocks take care of the damping over bumps and what not.

I see no ill effects of lowering your x this way except, ride quality. Get an alignment afterwards and all will be well. Just ask the ones who have been running this way, you won't be the first guy

[civdiv99]

Well, I don't think it's that simple. We can't use a tire or balloon analogy here. In something like a tire, lower pressure supporting the same weight requires the tire to spread out. That way lower psi has more square inches of area supporting the same weight.

The air suspension on our cars is significantly more restrictive in manner of "ballooning" with pressure changes. Think of it this way - suppose I want to support 1,000 lbs on a hydraulic jack, and I can choose to do so at 6" or 12" of height. In this admittedly extreme example, there is zero "ballooning," and therefore the height is strictly based on the volume of fluid pumped under the piston. The pressure of that fluid, at our example weight, will be exactly the same at 6" or 12" because the supported weight and the piston area supporting that weight are static. We just have more fluid in there.

While the suspension on our cars has some flexibility, it is substantially restricted compared to something like a tire or balloon. The area in sq inches the air can act on to support the weight doesn't materially vary at different heights. Lower the car 2", and you have reduced the static air volume in the bag via the control valve, but the air is supporting the same weight and doing so over "mostly" the same area. In other words, it's not restrictive like a jack cylinder would be, but it's not anything like a tire or balloon that can disburse our given weight over a much larger area. The static pressure will be lower only to the extent that more surface area is available - not in total but with respect to the area supporting the vehicles weight.

Separately from that, an air suspension is rising rate. If the area is fixed, and we force the volume to decrease, the pressure will increase. Air is compressible, of course, so we have a measure of compliance. Here's the point most folks miss - if I start with 100 cu. in. of static volume, and I decrease a given amount (bump), the pressure will rise a determinable amount. We all know that. But if I started instead with only 50 cu. in. of static volume, and I decreased the volume by the same bump, then the pressure delta, the increased pressure resulting from that volume change, would be twice as much. Rising rate characteristic means each subsequent increase in compression (bump) has a much larger effect on my spring rate than had I started with a higher static volume. "Compression ratio" if you will. Our suspension volume isn't that rigid, but it is not entirely flexy/squishy. We're somewhere in between.

Again, if the air suspension had a substantial capacity to balloon out and spread that pressure delta over much more surface area, then out compressed pressure would not spike much - it would disburse over the ballooning area. We don't have that extreme flexibility, though.

The point is that lowering the suspension will have a lower static pressure, just not as much as folks might think, because the surface area remaining to hold up the same vehicle weight is not markedly greater. Same weight, not much more area to apply the pressure to support the weight = small change in the pressure, but mostly a change in the volume via the valve (my jack analogy).

Smaller static volume, compressed a given amount by a bump, will have a correspondingly greater rate increase over that compression cycle vs that with the larger beginning static volume.

Noticeably firmer ride on rough roads.