Attention: TDR Forum Junkies 
grabinov
TDR MEMBER
Hey Gents,
Sorry for the long post. Hoping to help expand the knowledge base for the 2500 factory rear air ride.
In another installment (sorry, it's been a while) of: "Try to better understand and control your 2500 factory rear air suspension system", I've got an update on a project that it about a year in the making. About a year ago I installed a Thuren "leveling kit" on the front of my 2014 Ram 2500 with the goal of improving the ride in normal driving situations. I changed Springs, the Track Bar and King Shocks, and got exactly the improvement I wanted. The truck performs worlds better over everyday dips in intersections, local street speedbumps, parking lot square-edged speedbumps, etc. Incidentally, I had a similar (Kore Suspension) kit on my '04 with the same result - vastly improved performance for everyday driving. I have towed the same 12,000lb, 33 foot fifth wheel with both, and found the suspension upgrades only improved the performance even under heavy loads. BTW I added the rear track bar and King shocks in the rear too. More on that later.
Both trucks have/had rear air bags. The '04 had aftermarket Firestone bags and the current one has the factory air system. Interestingly, both trucks required the same adjustments in the rear in order to make the leveling kit effective. That is, when you put longer (taller) springs on the front level the truck, you can have the reverse occur when the truck is loaded - the back is now LOWER than the front. So what do you do if you want the truck level without the trailer and level with it? Again, in the '04 it was easy. You add air to the Firestone bags when the trailer is on.
The new truck is, well, weird. Stock, it runs with the rear higher than the front as is typical for most heavy duty pickups. That is in the "normal ride height" mode. For driving purposes, there is only one other mode, called "alternate ride height". (there are other modes for trailering the truck, doing wheel alignments, etc. but they are not used when moving). In the Alternate Ride Height mode, the truck sits level, and it stays that way if you add the weight of a trailer or weight in the bed, and I mean a lot of weight. It works.
So why not just leave it in that mode all the time? Legitimate question. Well some us can't leave well enough alone. We want our trucks lifted a little, and we want the improved performance of the aftermarket springs. I'm telling you, if you haven't ridden in a truck with Kore, Carli or Thuren springs, try it. You'll wonder why you didn't make the change the day you bought the truck. So I went looking for a way to do this with a factory air ride truck.
Well Thuren figured out the answer first as far as I can tell. And it was simple. The rear ride height (within limits) is controlled by two sensors which are moved by rods which "connect" the axle to the chassis. The truck senses the relationship between the axle and the chassis, and, in Alternate Ride Height mode, if that distance gets smaller, it adds air to the rear bags to get the height back to stock "level". Well that's not high enough anymore. Easy. Put in a longer sensor rod (from Thuren) so the truck thinks it's lower, and it will add air to push the back end up again. If you're thinking "That's not a leveling kit. It's a lift kit", you're exactly right. In Standard Ride Height, the truck sits with the bed slightly higher than the front, but it's much less noticeable that stock. The whole truck is lifted. The suspension is better, and in Alternate Ride Height mode, the truck is leveled, and stays that way under load. If you want your truck level, just run it in Alternate Ride Height all the time. Truck lifted. Truck Level. Works perfectly. BUT:
The pressure in the air bags is higher. In Alternate Ride Height mode the rear height is where it once was when in Standard mode, achieved by increasing pressure in the bags (all done automatically by the truck). The truck was designed to run this way in terms of both pressure and height, so no real harm is likely to come from this change.
In Standard mode the rear height is now higher than the stock Standard mode was, again achieved by increasing pressure in the bags (all done automatically by the truck). THIS, the truck was not designed for. The pressure to achieve this is well below the pressures the bags experience when loaded, so that's no big deal either. But the height of the bag is greater than as designed. Does this matter? I don't know, but from an engineering perspective, it's probably less than ideal. I had no solution until recently. Longer bags are made, but OMG am I not getting in between the computer and its pressurized air connection to the factory air bags without WAY more information than it seems any of us has on this system. We are still debating open vs closed loop system (open); system is "charged with nitrogen" (this is only the case because if the system is rarely used the nitrogen will result in more stable pressures as it is a larger molecule than air and leaks through the bag and hose material less than air); and so on.
But Carli came up with an answer. Old School. An air bag spacer! Just put a spacer of about an inch between the bag and the axle, or between the bag and the chassis, and you've done it. The bag is squished back to normal length and the pressure at any given height is back to stock. Carli's system looks very high tech and very expensive (but very neat). It's also very unavailable, and they no longer even sell to the public. They did put me onto a place called Top Tier suspension, who makes a kit, but it comes with a number of parts I don't need like limit straps (I'm not desert racing). It's pretty expensive too. It's not as high tech as the neat Carli design. Both of those systems mount on top of the bag. I would expect they are quality designs from quality companies, but I kept looking, and found Kelderman. I have not used their products before but I certainly know who they are. They sell the simple kit I was looking for (essentially just spacers and bolts), and theirs mount below the bags. I asked about this and they reasoned that it made no difference which end the spacers were on (as did I). The bag doesn't know, and the axle is located by the four link and by the track bar, not by the bag, which is soft and provides even less in the way of structure than would a spring.
So I'll be installing their kit. From their packaging and marketing materials alone you can see that these guys know their stuff and make a quality product. Let's see how the install goes. I'll update as I go...
And yes, the items in the top photo include:
An abalone iron
A Minion from Despicable Me
A Hot Wheels 1970 Roadrunner
A Lego motorcycle
A Ram steering shaft nut
and some bicycle tire parts...
Sorry for the long post. Hoping to help expand the knowledge base for the 2500 factory rear air ride.
In another installment (sorry, it's been a while) of: "Try to better understand and control your 2500 factory rear air suspension system", I've got an update on a project that it about a year in the making. About a year ago I installed a Thuren "leveling kit" on the front of my 2014 Ram 2500 with the goal of improving the ride in normal driving situations. I changed Springs, the Track Bar and King Shocks, and got exactly the improvement I wanted. The truck performs worlds better over everyday dips in intersections, local street speedbumps, parking lot square-edged speedbumps, etc. Incidentally, I had a similar (Kore Suspension) kit on my '04 with the same result - vastly improved performance for everyday driving. I have towed the same 12,000lb, 33 foot fifth wheel with both, and found the suspension upgrades only improved the performance even under heavy loads. BTW I added the rear track bar and King shocks in the rear too. More on that later.
Both trucks have/had rear air bags. The '04 had aftermarket Firestone bags and the current one has the factory air system. Interestingly, both trucks required the same adjustments in the rear in order to make the leveling kit effective. That is, when you put longer (taller) springs on the front level the truck, you can have the reverse occur when the truck is loaded - the back is now LOWER than the front. So what do you do if you want the truck level without the trailer and level with it? Again, in the '04 it was easy. You add air to the Firestone bags when the trailer is on.
The new truck is, well, weird. Stock, it runs with the rear higher than the front as is typical for most heavy duty pickups. That is in the "normal ride height" mode. For driving purposes, there is only one other mode, called "alternate ride height". (there are other modes for trailering the truck, doing wheel alignments, etc. but they are not used when moving). In the Alternate Ride Height mode, the truck sits level, and it stays that way if you add the weight of a trailer or weight in the bed, and I mean a lot of weight. It works.
So why not just leave it in that mode all the time? Legitimate question. Well some us can't leave well enough alone. We want our trucks lifted a little, and we want the improved performance of the aftermarket springs. I'm telling you, if you haven't ridden in a truck with Kore, Carli or Thuren springs, try it. You'll wonder why you didn't make the change the day you bought the truck. So I went looking for a way to do this with a factory air ride truck.
Well Thuren figured out the answer first as far as I can tell. And it was simple. The rear ride height (within limits) is controlled by two sensors which are moved by rods which "connect" the axle to the chassis. The truck senses the relationship between the axle and the chassis, and, in Alternate Ride Height mode, if that distance gets smaller, it adds air to the rear bags to get the height back to stock "level". Well that's not high enough anymore. Easy. Put in a longer sensor rod (from Thuren) so the truck thinks it's lower, and it will add air to push the back end up again. If you're thinking "That's not a leveling kit. It's a lift kit", you're exactly right. In Standard Ride Height, the truck sits with the bed slightly higher than the front, but it's much less noticeable that stock. The whole truck is lifted. The suspension is better, and in Alternate Ride Height mode, the truck is leveled, and stays that way under load. If you want your truck level, just run it in Alternate Ride Height all the time. Truck lifted. Truck Level. Works perfectly. BUT:
The pressure in the air bags is higher. In Alternate Ride Height mode the rear height is where it once was when in Standard mode, achieved by increasing pressure in the bags (all done automatically by the truck). The truck was designed to run this way in terms of both pressure and height, so no real harm is likely to come from this change.
In Standard mode the rear height is now higher than the stock Standard mode was, again achieved by increasing pressure in the bags (all done automatically by the truck). THIS, the truck was not designed for. The pressure to achieve this is well below the pressures the bags experience when loaded, so that's no big deal either. But the height of the bag is greater than as designed. Does this matter? I don't know, but from an engineering perspective, it's probably less than ideal. I had no solution until recently. Longer bags are made, but OMG am I not getting in between the computer and its pressurized air connection to the factory air bags without WAY more information than it seems any of us has on this system. We are still debating open vs closed loop system (open); system is "charged with nitrogen" (this is only the case because if the system is rarely used the nitrogen will result in more stable pressures as it is a larger molecule than air and leaks through the bag and hose material less than air); and so on.
But Carli came up with an answer. Old School. An air bag spacer! Just put a spacer of about an inch between the bag and the axle, or between the bag and the chassis, and you've done it. The bag is squished back to normal length and the pressure at any given height is back to stock. Carli's system looks very high tech and very expensive (but very neat). It's also very unavailable, and they no longer even sell to the public. They did put me onto a place called Top Tier suspension, who makes a kit, but it comes with a number of parts I don't need like limit straps (I'm not desert racing). It's pretty expensive too. It's not as high tech as the neat Carli design. Both of those systems mount on top of the bag. I would expect they are quality designs from quality companies, but I kept looking, and found Kelderman. I have not used their products before but I certainly know who they are. They sell the simple kit I was looking for (essentially just spacers and bolts), and theirs mount below the bags. I asked about this and they reasoned that it made no difference which end the spacers were on (as did I). The bag doesn't know, and the axle is located by the four link and by the track bar, not by the bag, which is soft and provides even less in the way of structure than would a spring.
So I'll be installing their kit. From their packaging and marketing materials alone you can see that these guys know their stuff and make a quality product. Let's see how the install goes. I'll update as I go...
And yes, the items in the top photo include:
An abalone iron
A Minion from Despicable Me
A Hot Wheels 1970 Roadrunner
A Lego motorcycle
A Ram steering shaft nut
and some bicycle tire parts...
Last edited:
