Air Suspension on 3500

[AH64ID]

Here again, I must be missing something, how do bumps become less "harsh" when you've added spring rate? Unless your definition of harsh is different than mine?

Having the right amount of spring rate for the weight will always ride the best. Too much spring rate, or too little spring rate won't ride as nice. Too much is jarring and harsh while too little is spongy and harsh when you bottom out or move excessively for the road conditions.

So if the OEM springs are withing their capacity but they are near the top of that capacity the added spring rate will result in a better ability to support the load and that in turn creates a better riding truck.

If you take a 1/2 ton and a 3/4 ton and put them both at 3,900 on the rear axle the 3/4 ton will ride better, even thou it has a stiffer spring rate.

 

[kthaxton]

Agreed, I understand that perfectly. I guess this comes down to our definitions of "harsh" being different.

 

[AH64ID]

Agreed, I understand that perfectly. I guess this comes down to our definitions of "harsh" being different.

Not sure what the difference would be. Harsh means rough or jarring. Airbags on stock springs do a great job of reducing the rough and jarring ride, if you inflate them properly.

 

[kthaxton]

Not sure what the difference would be. Harsh means rough or jarring. Airbags on stock springs do a great job of reducing the rough and jarring ride, if you inflate them properly.

To me, rough, harsh and perhaps jarring is what you get with a stiff suspension, similar to what it would be like to ride around with 80 psi in your tires all the time. I don't see how it could less harsh, when the suspension has been stiffened.

 

[PT02063]

"I aired the bags to 30# LOADED it did not change the ride height but made a HUGE difference in the ride.

I believe this is where the conversation goes sideways...you have the ability to variably add/remove air whereas the stock 2500 system is a sealed system which has one button and two specific settings - Normal Load Leveling and Alternate Ride Height mode.

Normal Load-Leveling Mode.
In this mode, the system monitors the ride
heights on both sides of the vehicle, adjusting for shifts in the load or
changes in road surfaces; you’ll welcome the constant level load profile and
proper headlamp-to-road angle, especially during heavy hauling assignments.

Alternate Ride Height Mode.
This mode lowers the rear suspension about
an inch—just right to keep the hitch/trailer alignment even. It also establishes
capable and comfortable towing by creating a parallel and level relationship
between the vehicle and the trailer, ensuring an even “rake” from the front
of the pickup through the trailer.

And it is this system to which I'm referring (on my 2017 2500 and available on the 2017 3500 also) which does not ride as nicely because one can't vary the pressure in the bags for ride as it is only for leveling purposes. Both you and AH64ID are able to vary the amount of air in your bags whereas the new factory version don't give you that option. Granted, I can vary tire pressure to achieve a little better ride but one can only do so much with it before it becomes a detriment to the tire and the tire monitoring system.

 

[kthaxton]

You said it yourself, here:

Having the right amount of spring rate for the weight will always ride the best. Too much spring rate, or too little spring rate won't ride as nice. Too much is jarring and harsh while too little is spongy and harsh when you bottom out or move excessively for the road conditions.

How could adding spring rate make it less harsh?

I understand that bottoming out would be considered harsh, but I normally don't consider bottoming out a typical situation when describe how something rides....because if you are bottoming out reasonably often, something needs to be corrected.

 

[AH64ID]

I believe this is where the conversation goes sideways...you have the ability to variably add/remove air whereas the stock 2500 system is a sealed system which has one button and two specific settings - Normal Load Leveling and Alternate Ride Height mode.

Normal Load-Leveling Mode.
In this mode, the system monitors the ride
heights on both sides of the vehicle, adjusting for shifts in the load or
changes in road surfaces; you’ll welcome the constant level load profile and
proper headlamp-to-road angle, especially during heavy hauling assignments.

Alternate Ride Height Mode.
This mode lowers the rear suspension about
an inch—just right to keep the hitch/trailer alignment even. It also establishes
capable and comfortable towing by creating a parallel and level relationship
between the vehicle and the trailer, ensuring an even “rake” from the front
of the pickup through the trailer.

And it is this system to which I'm referring (on my 2017 2500 and available on the 2017 3500 also) which does not ride as nicely because one can't vary the pressure in the bags for ride as it is only for leveling purposes. Both you and AH64ID are able to vary the amount of air in your bags whereas the new factory version don't give you that option. Granted, I can vary tire pressure to achieve a little better ride but one can only do so much with it before it becomes a detriment to the tire and the tire monitoring system.

You do realize we are discussing the 3500 air-assist and that Cummins12V98 owns one right?

I’m talking about mine because a side topic got started about airbags in general.

You said it yourself, here:



How could adding spring rate make it less harsh?

I understand that bottoming out would be considered harsh, but I normally don't consider bottoming out a typical situation when describe how something rides....because if you are bottoming out reasonably often, something needs to be corrected.

Because it’s the proper spring rate for the weight. Proper spring rate will handle the best. As rear axle weight increases it may take more spring rate to obtain the best handling and ride.

The same thing can be said for stiffer shocks. Stiffer shocks can ride better when they are properly matched to the load/spring rate.

That’s the great thing about the OEM system is it adjusts for every load and will create a better ride and handling without driver input, aside from possibly pressing the alt ride height button.

 

[kthaxton]

Because it’s the proper spring rate for the weight. Proper spring rate will handle the best. As rear axle weight increases it may take more spring rate to obtain the best handling and ride.

Again, agreed, I understand this, I just wouldn't refer to supporting the load better (i.e. because of increased spring rate to handle such load) as making the ride less harsh. I think our definitions just differ.

The same thing can be said for stiffer shocks. Stiffer shocks can ride better when they are properly matched to the load/spring rate.

I agree with that too, but we are talking apples and oranges now. Soft shocks would give a poor ride with a heavy load because they wouldn't control the suspension well, it would be bouncy and spongy. I would not describe that type of ride as harsh. Stiff shocks would give a better ride with a heavy load because they control the weight better and stop the bouncing sooner.

 

[AH64ID]

Again, agreed, I understand this, I just wouldn't refer to supporting the load better (i.e. because of increased spring rate to handle such load) as making the ride less harsh. I think our definitions just differ.

You said you understand how it works on the OEM setup, but you don't understand it on an aftermarket airbag setup. That's confusing, as they both work on the same principle. As air pressure in the bags increases the spring rate increases, regardless if they are aftermarket or OEM airbags.

To me the benefit of air suspension, weather complete or supplemental, is all about variable spring rate. Lower spring rate when empty and heavier spring rate when loaded.

In terms of the definition of harsh I am having The Princess Bride flashbacks, so I have to ask... what do you think harsh means?

It sounds like you think something can be harsh and properly handle the load.

I agree with that too, but we are talking apples and oranges now. Soft shocks would give a poor ride with a heavy load because they wouldn't control the suspension well, it would be bouncy and spongy. I would not describe that type of ride as harsh. Stiff shocks would give a better ride with a heavy load because they control the weight better and stop the bouncing sooner.

Improper shocks can very easily give a harsh ride, just like improper spring rate. Unfortunately I have experience with both.

 

[kthaxton]

You said you understand how it works on the OEM setup, but you don't understand it on an aftermarket airbag setup.

I said I understand how the factory air ride gives a better overall ride. It is less harsh because it can have only the spring rate that it needs. That is not the same as saying you can add airbags to an existing truck, and somehow have a less harsh ride.

so I have to ask... what do you think harsh means?

I already explained what it means to me.

Improper shocks can very easily give a harsh ride, just like improper spring rate.

Yes, but adding stiffer shocks, won't make the ride LESS "harsh".

This is getting muddled up, just to clarify, with the typical definition of a harsh (stiff) ride, I don't see how you can make it LESS harsh, by INCREASING the spring rate.

 

[AH64ID]

I said I understand how the factory air ride gives a better overall ride. It is less harsh because it can have only the spring rate that it needs. That is not the same as saying you can add airbags to an existing truck, and somehow have a less harsh ride.

That's the exact same way aftermarket airbags work. The spring rate is adjusted for each load, somewhere from 5-100 psi. It's up to the end user to determine the proper air, which is where most people screw up and add too much and make the ride more harsh by having too much spring rate for the weight.

It's exactly the same principle, zero difference.

The OEM setup needs more air for the same rear axle weight due to a softer spring pack, but otherwise it works the same by adding air to increase spring rate.

Yes, but adding stiffer shocks, won't make the ride LESS "harsh".

They can if the first ones weren't valved properly. Stiffer doesn't mean harsher if you were too soft at first.

This is getting muddled up, just to clarify, with the typical definition of a harsh (stiff) ride, I don't see how you can make it LESS harsh, by INCREASING the spring rate.

The same way the OEM air-assist does, but increasing spring rate to handle increased load. It's about maintaining a constant ratio of weight to spring rate, and when that ratio is met the ride is less harsh. Empty is going to be the harshest ride in a HD pickup as the spring rate is much higher than the weight, which is why people recommend the ALT ride height on the air-assist and to let the rear sink 1" or so on aftermarket airbag setups.

At this point all I can say is that it's something you would have to experience first hand to understand.

 

[kthaxton]

It seems I need to back up again, and get more detailed.

That's the exact same way aftermarket airbags work. The spring rate is adjusted for each load, somewhere from 5-100 psi. It's up to the end user to determine the proper air, which is where most people screw up and add too much and make the ride more harsh by having too much spring rate for the weight.

The OEM setup needs more air for the same rear axle weight due to a softer spring pack, but otherwise it works the same by adding air to increase spring rate.

Again, it seems our definitions of "harsh" differ, and I am not contradicting myself.

In regards to how the factory air ride fits into this discussion....it really doesn't. I was merely clarifying that I understand the concept of how it allows the right spring rate, for varying loads, therefore a better ride. There was NO comparison made with the factory air ride under to two conditions, i.e. adding or lowering pressure to make the ride more or less harsh. This was not brought up as a means of comparison....which it would have to be if we were to apply my understanding of that, to be a parallel discussion to the actual discussion, or at least, where I came into it to disagree (wow, that sentence almost confuses me!).

With the factory leaf sprung truck, with aftermarket air bags, a comparison was made. This is where I disagree.

First, say we have a DRW factory leaf sprung truck with a 3000 lbs load, and we drive it, it's likely not very harsh but lets pretend it was. Now, we add air bags.....even at the lowest pressure (and yes, I understand the operator has the ability to adjust this and should, properly), the spring rate can only go up, not down. It would still have an increased spring rate vs this truck prior to the air bag install.

When we make THIS comparison, I do not see how with an increased spring rate, that the ride would be LESS harsh than with just the factory leafs (if it would even be able to be described as harsh beforehand, because to me, it would be harsh unloaded, but not loaded). Yes, it would handle the load better, give better manners in corners and just all around have a better ride....but I don't see how it could be deemed less "harsh" (again, going with my description of what harsh means, which you haven't actually said you disagree with). If the ride was harsh before, it certainly couldn't be less harsh because we've increased the spring rate, it would actually be more harsh, assuming it was harsh to begin with.

My understanding of how a factory air ride would ride better in all conditions, does not contradict my not understanding that you say it would be less harsh with a higher spring rate.....so we can keep that out of the discussion.

It's exactly the same principle, zero difference.

No, it's not. In this case we are talking about the right pressure, under all circumstances (factory air). With the addition of bags to a factory leaf sprung vehicle, the spring rate can ONLY go up, not down. There is no scenario where adding more spring rate, will make a given load less harsh to haul. It will make it ride better, of course, but not make a harsh ride less harsh.

Empty is going to be the harshest ride in a HD pickup as the spring rate is much higher than the weight,

See, you get it here. If you have a harsh ride already, increasing the spring rate under a given load will only make it harsher, not less. Think of it this way, with an empty HD truck with aftermarket bags, would adding more air to the bags make the ride LESS harsh? No, it would not.

 

[MarkEagleUSA]

I don't have a dog in this fight nor do I have (or have ever used) air bags, but wouldn't they act as a damper and remove some of the "harshness" even if the spring rate is increased?

 

[AH64ID]

Again, it seems our definitions of "harsh" differ, and I am not contradicting myself.

I'm using the Websters definition to try to take any "assumption" of meaning out of it. From the dictionary harsh is "unpleasantly rough or jarring to the senses"

When we make THIS comparison, I do not see how with an increased spring rate, that the ride would be LESS harsh than with just the factory leafs (if it would even be able to be described as harsh beforehand, because to me, it would be harsh unloaded, but not loaded). Yes, it would handle the load better, give better manners in corners and just all around have a better ride....but I don't see how it could be deemed less "harsh" (again, going with my description of what harsh means, which you haven't actually said you disagree with). If the ride was harsh before, it certainly couldn't be less harsh because we've increased the spring rate, it would actually be more harsh, assuming it was harsh to begin with.

What you claim your definition of harsh is and how you use the word appear to be two very different things.. hence me asking how you define it even thou you already had.

I have explained, many times, how increased spring rate can reduce harshness. It comes down to the meaning of the word, and why I quoted the dictionary.

My understanding of how a factory air ride would ride better in all conditions, does not contradict my not understanding that you say it would be less harsh with a higher spring rate.....so we can keep that out of the discussion.

It is absolutely contradictory. If the ride is better it is less harsh.

No, it's not. In this case we are talking about the right pressure, under all circumstances (factory air). With the addition of bags to a factory leaf sprung vehicle, the spring rate can ONLY go up, not down. There is no scenario where adding more spring rate, will make a given load less harsh to haul. It will make it ride better, of course, but not make a harsh ride less harsh.

The factory setup does not constantly change pressure as you hit a bump or a rut going down the road at 70. It has a time delay to maintain pressure based on load an not on road conditions.

I'm curious how you think the spring rate of the OEM air-assist can go down? At curb weight the truck is at it's lowest spring rate, it can ONLY go UP... which is the basis of your argument for why it can only be harsher with an aftermarket setup.

As Cummins12V98 mentioned it takes a load of approx 500lbs to be able to remain in ALT ride height, this is becuase without the added weight of 500 lbs there isn't enough weight on the rear axle to allow the springs to sag the 1" and maintain minimum pressure in the bags... i.e. spring rate cannot go down from the base setting without any weight in the bed.

The principal is IDENTICAL..only a truck that starts without OEM air-assist begins with a higher spring rate and thus should wait until a higher rear axle weight is obtained to add air pressure, but how they work is identical.

See, you get it here. If you have a harsh ride already, increasing the spring rate under a given load will only make it harsher, not less. Think of it this way, with an empty HD truck with aftermarket bags, would adding more air to the bags make the ride LESS harsh? No, it would not.

No it doesn't. Proper spring rate will absolutely reduce jarring and unpleasant roughness...which is the definition of harsh. It's not my definition, but the definition.

 

[AH64ID]

I don't have a dog in this fight nor do I have (or have ever used) air bags, but wouldn't they act as a damper and remove some of the "harshness" even if the spring rate is increased?

Absolutely, as long as they are not overinflated for the load.

 

[zb39]

I have plenty of experience with both. I drove my 2011 DRW 3500 45k miles empty, hauling my AF TC, or my 5th wheel. I then got the 2016 DRW 3500 with factory air. It rode better in all 3 modes. Empty, with TC, or with 5th wheel. 22k miles so far. In fact it rode so much better my wife is upset I ordered a 5500 C & C. But thats another story. Think what you want but my 2 trucks were quite similar and the Air ride rode better and still does. When you look at the 2 different spring packs it's obvious why one rides better than the other.

 

[Cummins12V98]

I don't have a dog in this fight nor do I have (or have ever used) air bags, but wouldn't they act as a damper and remove some of the "harshness" even if the spring rate is increased?

YES, they absorb some of the impact. I think of it as if you stomp your foot on the ground you will feel the impact to a certain degree. Now lay a firm 1" thick sponge on the ground and stomp just as hard, the impact you "FEEL" will be less.

 

[kthaxton]

I'm using the Websters definition to try to take any "assumption" of meaning out of it. From the dictionary harsh is "unpleasantly rough or jarring to the senses"

Yep, that's pretty much what it means to me. I suppose none of the rest of what you typed on this particular subject is worth rebutting because it appears we are at an impasse and we'll have to agree to disagree....because I cannot fathom how the ride for a given load would be LESS "rough or jarring" by adding more spring rate.

It is absolutely contradictory. If the ride is better it is less harsh.

No, it is not (contradictory). You are using harsh and ride interchangeably. I am not.

The factory setup does not constantly change pressure as you hit a bump or a rut going down the road at 70. It has a time delay to maintain pressure based on load an not on road conditions.

I did not say this. I said it will have the right pressure under all circumstances (meaning the load). I know it doesn't change constantly. When you add or remove weight, it adjust to the right pressure.

I'm curious how you think the spring rate of the OEM air-assist can go down? At curb weight the truck is at it's lowest spring rate, it can ONLY go UP... which is the basis of your argument for why it can only be harsher with an aftermarket setup.

You totally missed what I am saying.....and am tired of repeating myself.

The principal is IDENTICAL..only a truck that starts without OEM air-assist begins with a higher spring rate and thus should wait until a higher rear axle weight is obtained to add air pressure, but how they work is identical.

Exactly! It's already at a higher spring rate, add air bags and it can ONLY go up. If the ride is already "harsh" because of the stock spring rate and the load it has (small or no load obviously), it will only get MORE harsh by adding air bags. I cannot figure out why this is so hard to understand?

No it doesn't. Proper spring rate will absolutely reduce jarring and unpleasant roughness...which is the definition of harsh. It's not my definition, but the definition.

Ugh.....see, here you are saying "proper" spring rate will reduce jarring and unpleasantness...I am not arguing about "proper" spring rate, I am talking about an existing harsh ride, will not get less harsh by adding spring rate. It will be less harsh by REDUCING spring rate. It's like you are purposely ignoring the terms I am using.

 

[NIsaacs]

Supplemental air bags on a spring equipped vehicle don't really add spring rate, they alternate the spring rate. They remove weight off the springs and add it to the bag. The weight is now divided between the springs and the bag, but the weight is the same. The "spring rate" changed but didn't increase. The spring rate is now different in how it is controlled. The way a spring handles the weight is different in how a bag handles it. Springs in general have a lot of compression movement, not so with the air bag. So too much air will give a rough ride. They are not as forgiving as you would think.

On an air bag "only" equipped vehicle (no springs) more air in the bag means a higher spring rate. More air in the bag to supplement the springs just changes where the weight is carried. If I add air to a supplemental bag to raise the vehicle level, it is no different than adding a 2x4 between the springs and axle, the spring rate did not increase, just the height where it is carried.

An air bag also changes it's given air pressure based on load or bump. If I put 10# of air in empty, then add 2 ton of weight, the air pressure will go up. So even tho they are similar to a tire, they are different. When you add weight to a tire the pressure don't change.

Does this make sense or am I off in La La land

Nick

 

[AH64ID]

because I cannot fathom how the ride for a given load would be LESS "rough or jarring" by adding more spring rate.

It's obvious you've never done it....

I've explained it to you, several times. Overall spring rate does increase, as you aren't sagging as hard, but the way the weight is carried is different and produces a less harsh ride.

No, it is not (contradictory). You are using harsh and ride interchangeably. I am not.

Absolutely contradictory. I'm not using them interchangeably. I'm simply stating that by definition if the ride is better it is less harsh. You cannot have a better ride be harsher.

Exactly! It's already at a higher spring rate, add air bags and it can ONLY go up. If the ride is already "harsh" because of the stock spring rate and the load it has (small or no load obviously), it will only get MORE harsh by adding air bags. I cannot figure out why this is so hard to understand?

All I can guess is you've never used airbags, and if you have you haven't used them properly.

Look at it this way, I think we're all on the same page that a level truck rides the best and is the least harsh.

If I put 6K on my rear axle with the stock springs I'm going to sag below level, and the rear springs will be riding on the thick lower overload which increases spring rate but does not raise the vehicle, it also reduces available spring movement. I then add air into the airbags (just like the OEM setup will) until I have raised the truck back to level, which is ~1.5" below my empty ride height. I have increased the ride height so I've increase spring rate, but I have also put the truck in a level position and it's no longer completely sitting on the thick overload. The spring rate is now being shared between the springs and the airbags, and neither one is maxed out. This gives a better, less harsh, ride by allowing the spring/bag more movement as the spring has less weight on it. When all the weight is on the spring it doesn't have the ability to move as much over rough conditions which makes it more harsh. Also as pointed out the volume of air adjusts as the suspension cycles up and down, so over really rough terrain the spring rate is more variable and helps control the load better.

More control and a better ride will reduce the rough/jarring feeling and thus it's less harsh.

If that doesn't help then I have nothing else to add. It works, we're telling you that, so trust us that do it on a regular basis.

Ugh.....see, here you are saying "proper" spring rate will reduce jarring and unpleasantness...I am not arguing about "proper" spring rate, I am talking about an existing harsh ride, will not get less harsh by adding spring rate. It will be less harsh by REDUCING spring rate. It's like you are purposely ignoring the terms I am using.

If you agree that proper spring rate will reduce jarring and unpleasantness then you agree that proper spring rate will reduce harshness. This is where it gets contradictory.

Too little spring rate can create a harsh ride, which is why adding spring rate will reduce harshness. I've said this several times.

NIssacs comment on how the load is carried, even with the increased spring rate, is very valid as well.

Does this make sense or am I off in La La land

Why can't it be both :-laf