Factory Rear Air Suspension Question

[DeansRedRam]

Only 5,750# pin weight and 9,750# RAW in this pic. Truck sets EXACTLY the same unloaded. Both pics in ALT ride mode.

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Holy Cow, you had almost 6000lbs in the bed and it was still level? Thats incredible.. Even all the research and talk about the rear air in my truck I'm not 100% on what that "Alt Trailer Height" button does. The only real time I towed with the truck I didn't have the time to pay mind to the operation of the system.

 

[lpennock]

Holy Cow, you had almost 6000lbs in the bed and it was still level? Thats incredible.. Even all the research and talk about the rear air in my truck I'm not 100% on what that "Alt Trailer Height" button does. The only real time I towed with the truck I didn't have the time to pay mind to the operation of the system.

Alt Trailer Height just drops the rear about 1" under load over the normal loaded height which is about 0.5 to 1" under the unloaded height on my 18 drw.

 

[DeansRedRam]

Alt Trailer Height just drops the rear about 1" under load over the normal loaded height which is about 0.5 to 1" under the unloaded height on my 18 drw.

Gotcha. So if I loaded a trailer and didn't press that button, it would maintain that factory rake, correct?

I guess when in "Alt Trailer Height", it levels it to put more load on the spring and thus, maybe a softer ride? Utilizing the suspension a bit more?

 

[lpennock]

Gotcha. So if I loaded a trailer and didn't press that button, it would maintain that factory rake, correct?

I guess when in "Alt Trailer Height", it levels it to put more load on the spring and thus, maybe a softer ride? Utilizing the suspension a bit more?

My 18 will drop about 1" from unloaded to 4500 lb in the bed. Close enough to factory rake your naked eye won't notice. If I engage Alt it will drop another inch but it still looks mostly level. Not like the sprug models that crop 3" or so when loaded.

 

[AH64ID]

Alt Trailer Height just drops the rear about 1" under load over the normal loaded height which is about 0.5 to 1" under the unloaded height on my 18 drw.

When the suspension drops that 1 inch it now engages the lower overloads as well. The lower overloads are massive and really help improve role stability and overall handling. To me that is the biggest benefit to alternate ride height.

If I leave my truck in alternate ride height mode and remove my payload it will return to the normal ride height even though the dash says alternate. It’s just the strength of the actual springs and the minimum pressure in the bags increasing the ride height.

 

[DeansRedRam]

That would explain why there's no sway bar back there. My friend with a 3500 SRW w/o factory air doesn't have a sway bar either.

My 01' with factory heavy duty overloads has a factory sway bar as well.

I guess I have to do more testing myself of how this truck works.

 

[SnoKing]

That would explain why there's no sway bar back there. My friend with a 3500 SRW w/o factory air doesn't have a sway bar either.

My 01' with factory heavy duty overloads has a factory sway bar as well.

I guess I have to do more testing myself of how this truck works.

Rear sway bar went away in 2003 when the frame rails were widened. SnoKing

 

[DeansRedRam]

Rear sway bar went away in 2003 when the frame rails were widened. SnoKing

Interesting! Didn't know that.

I now wonder if Ford has a sway bar, or Ram duallys.

I wish ram had the overload spring on 3500 SRW like an F350 SRW does.

 

[AH64ID]

Only HD Ram with a rear anti-sway bar is a 2500.

Some Furds have them.

 

[SnoKing]

Interesting! Didn't know that.

I now wonder if Ford has a sway bar, or Ram duallys.

I wish ram had the overload spring on 3500 SRW like an F350 SRW does.

Did you fail to look at my picture and load in post #12 ????? Most Ford owners end up adding airbags because of weak springs for empty ride quality!

 

[lpennock]

I now wonder if Ford has a sway bar, or Ram duallys.

No Sway bar on the Ram Dually. I added a Roadmaster to mine to control the sway with the big cabover camper. The Airbags have less control than the outboard extra overloads that were on the earlier trucks.

 

[Cummins12V98]

"So if I loaded a trailer and didn't press that button, it would maintain that factory rake, correct?"

This is TRUE!!!

Watch the TFL fuel economy test they did NOT have the truck in aLT. They measured to the inside of the rear fender at 40". My Truck sets ay 38 3/4" in ALT. Sets the same unloaded or 6k in the bed.

 

[AH64ID]

I wish ram had the overload spring on 3500 SRW like an F350 SRW does.

My 05 3500 SRW had overloads and they were mostly useless. They didn't engage statically until the rear axle was at tire capacity, so to me that's fairly pointless. The 2010+ 3500 SRW spring trucks have the slightly higher spring rate spring pack, 7% stiff IIRC. So even with the higher RAWR the overloads wouldn't be worth it, which is likely why Ram dropped them from the 3500 SRW.

No Sway bar on the Ram Dually. I added a Roadmaster to mine to control the sway with the big cabover camper. The Airbags have less control than the outboard extra overloads that were on the earlier trucks.

My load isn't quite as high as yours but I do put 2 ATV's above the bed rails. My 05 had airbags and a Hellwig anti-sway bar. The 18 is far more stable with the same load than the 05. I think it's a combo of the frame and the large overloads that are engaged in ALT.

 

[lpennock]

My load isn't quite as high as yours but I do put 2 ATV's above the bed rails. My 05 had airbags and a Hellwig anti-sway bar. The 18 is far more stable with the same load than the 05. I think it's a combo of the frame and the large overloads that are engaged in ALT.

Let me clarify what I'm saying on the air suspension against the older style suspension. On my 06 carrying a 4K camper the evolution of the suspension went like this.
1. No modification. I didn't like how low the rear set and it just barely used the overloads as the main leafs carried most of the load.
2. I added Air Aide Aircells. These replaced the factory bump stops just like Timbrens. Because the bumpstops set inside of the frame rails the camper sway increased. This is very similar to what the stock 18 factory air felt like; however I do think the 18 was a bit better controlled and it definitely rides smoother. Part of the additional fealingof control on the 18 could have been shorter sidewalls and duals though.
3. I then added the Torqlift stableloads that replace the bump stops for the factory upper overloads. This got rid of the sway while keeping the rear sag in check.
4. I felt I didn't need the air cells so I readjusted them to act more like bump stops. I.e. they were about a 1/2" above the axle when loaded so they would only come in on a harder bumps. This is where I ended with the 06. I feel the loaded ride was about the same as the 18 but the unloaded is better on the 18. This is the configuration that I said has better sway control than the stock 18 or any airbag only modification.

On the 18, since I didn't like the lack of sway control that inside the frame bags provided, I added a Roadmaster rear sway bar. (Slighter bigger than a Helwig Big Wig but my reason for using it was I preferred the axle mount better). The sway bar got the 18 up to the same or maybe slightly better sway control than I had in config 4 above. The shorter sidewalls and duals on the 18 over the 06 with 295/70r18(34") tires make it hard to be sure but it is good enough I don't feel uncomfortable on winding roads like I did before adding the bar.

Bottom line is the further outboard the load carrying is, the less sway the truck will have. In board air bags, especially if tied together to a common air supply (as opposed to separate inflation control on each bag) aggregate the sway all other things being equal. Simple laws of physics and moment arms.

 

[SnoKing]

Bottom line is the further outboard the load carrying is, the less sway the truck will have. In board air bags, especially if tied together to a common air supply (as opposed to separate inflation control on each bag) aggregate the sway all other things being equal. Simple laws of physics and moment arms.

I made that criticism of the air system on the 3500 when it was first revealed. SnoKing

 

[Cummins12V98]

I would be concerned to put a BIG truck Camper on mine. But I have heard it would do fine.

I can say towing 24k with 25% pin of 6k the ride is rock solid. I have towed in some bad AZZ winds.

 

[SnoKing]

I would be concerned to put a BIG truck Camper on mine. But I have heard it would do fine.

I can say towing 24k with 25% pin of 6k the ride is rock solid. I have towed in some bad AZZ winds.

The 5th wheel force on the truck is at the hitch plate level and that plate has side to side tilt. A 10.5-11.5' TC puts much more side force in the trucks frame

 

[Ozymandias]

"It won’t error out even above the DRW RAWR"

I can attest this is true! Last I weighed my RAW was 10,560# with ZERO warnings and the truck still sat exactly as it always has loaded or unloaded.

Make sense, it must be at least built for RAWR and a safety margin. Until someone tests it out with sand bags in the bed we'll never know how much safety margin Ram designed into the Airspring setup.

 

[DeansRedRam]

"So if I loaded a trailer and didn't press that button, it would maintain that factory rake, correct?"

This is TRUE!!!

Watch the TFL fuel economy test they did NOT have the truck in aLT. They measured to the inside of the rear fender at 40". My Truck sets ay 38 3/4" in ALT. Sets the same unloaded or 6k in the bed.

View attachment 119104

Wow, 6k that's IMPRESSIVE. I think my rear tires will pop before my truck will squat on my truck lol

 

[Mingoglia]

Here's another testament for the factory air on my '15 dually. Even at over 10,000lbs (weighed it on the scale), my truck still sits level and doesn't complain. I've turned the suspension on "transport mode" and back to regular mode many times while putting on the weight distribution bars. I use the air suspension to my advantage when releasing the tension. Brings the load to level as quickly with 6k in the bed (truck camper) and 1k of tongue weight as it does with a small load.