In Bob's case he is needing increased air pressure, above the base amount needed for the 2" lift, to handle the added load of his trailer. So perhaps the ping tank would help for the trailer-on case, but not for trailer-off. However that would make the system more complicated. I hope Bob's suspension guy is familiar with his type of issue; look forward to hearing what they have to say.
Bob's case if a tough one, I think, as we really aren't sure (at least I am not) what kind of motion is causing his symptoms of things falling off hooks in the trailer. It could be from low spring rate big oscillations or from too high spring rate quick bursts of movement, I would guess. Because of this, I don't know if he would benefit from higher or lower spring rate in the rear, but higher damping rate in the shocks probably would be nice to have when towing.
I keep going back to the "what changed" with the lift in the rear and front. Pivoting around the higher spring rate in the front is certainly one of the possibilities, and I think the other big one is the relationship of the trailer to the van hitch. Normally, if you would do a 2" lift of the tow vehicle rear, you would also need to raise the trailer hitch or lower the tow vehicle hitch by the same amount to keep all things like hitch weight and distribution settings the same. If you just let the distribution setup take it up, the rear weight, and front weight will change, as will tongue weight and load distribution on the front and rear trailer tires. A lot of stuff changes.
I, too, am eager to hear what a towing expert has to say as I think it could be a good education for all of us. Bob has been towing heavy a long time, so I am sure he will come up with a good solution.
Pete, Booster,
Thanks Pete. I just got around to going thru Google hits on "Ping Tanks". Fascinating reading. So I have some exploring to do to find a suspension shop that seems tuned in on this.
In the mean time I want to throw something else out for your thoughts too.
I towed the same trailer with our 2004 RT 190 since the RT was nearly new without tools hopping of hangers in the front of the trailer. Could a change in rear OEM springs account for the more prominent rear end hop in the 2013 RT than the 2004? When I bought the 2013 RT 190 I almost immediately installed the Moog front springs, the rear axle Airlift bags, and Bilstiens without driving or towing hardly at all so my impressions prior to the modifications are inconclusive.
And its is worth noting that I get the prominent hop (and tools hopping off hangers) in the 2013 even with the air bags defalted to 5 - 10 PSI and the prominent hop is with the trailer on or off. This seems really odd to me if the cause of the hop is the airbags. So I am suspicious that the root cause might not be air bag related but due to a difference in OEM rear springs between the 2004 and 2013??
I guess a call to a Chevy dealer to see if there was a part number change for rear springs between 2004 and 2013 would be my next simple step on this. Then a call to the really GOOD RT specialty shop in Gainesville to see if repeat customers had said anything about perceived change in rear ride quality during trade-up times or if their delivery driver who has moved A LOT of RTs had noticed any differences over those years.
BTW, I did swap the rear Bilstien shocks to NAPA shocks that were their higher quality/price units without improvement in rear end hop in the 2013.
Hi Bob, I don't recall if you have the airbags that have the internal bump stops, or not.
If you do have the ones with bump stop, it will probably hold up the rear a bit off of the overload leaf, even with the air out or very low. Look at the forward side of the overload and see how much room you have between to end of the overload and the next up leaf. A typical 190 seems to be very close or touching the next spring leaf in stock form. What we found in ours was that if it we were off the spring by an amount that was within how the much the spring compressed on moderate to bigger bumps, we actually got more harshness that if were sitting on or much closer to the overload. The mass of the vehicle hitting the overload leaf, which is very stiff, would give us a harsh jolt and often and audible slap (the "pad" on the overload where it hits is not soft). If we got high enough off, it would be eliminated on moderate bumps and only showed up on big ones. That may be what is going on with yours, and the older van is very likely sitting on the overload all the time, so stiffly sprung, but not slapping the overload and getting shocked. On ours, I finally decided to just see what happened if I removed the overload leaf, once I put in bags with the bumpstops in case a bag popped. With no overload to hit, the rear ride got smoother and quieter. You can feel it has more travel in compression now, but it just goes smoothly onto the bump stops in the bags I think, if it is too big a bump. We have been very happy with the change, which has been in a few years now, but we don't tow regularly.
Bob,
I hope booster’s experience helps provide a simple solution (remove the overload spring). I have come across some other information that connects somewhat with booster’s experience.
A few years back Firestone came out with the R4Tech suspension system. A key element of the R4Tech is that the stock springs are removed and replaced with what looks like much lower spring rate springs with no overload spring. So the airbag handles most of the spring requirement. There are other elements of the R4Tech, such as a J-link spring and variable damping shocks that use the air bag pressure to regulate the damping. These shocks look like what I had in my F350 that I mentioned earlier. Firestone discontinued this system, I assume because of the high cost and insufficient sales.
Sdtrucksprings still shows the R4Tech on their site. Summitracing has a link to an installation manual. Perhaps one of them can provide you with installers in Florida or Maryland (your other home place???). Hopefully a shop that has installed these is familiar with issues like yours and can offer a sensible solution.
Here is a link to an installation manual. And a few sketches and pages from the Firestone catalog that briefly describes the system.
That is a very interesting system from Firestone. It looks like they took it further to the softer spring side than we did, and it is likely that the spring is carrying a very low percent of the weight compared to us. We have probably 60% of more of the weight still on the spring.
It looks like what they have made is a simple swing arm at the front segment of the spring and are still using the spring attachment points to handle the side load so no track bar needed. On the Chevies, like most overload spring setups, does not have the overload leaf connected to either spring eye and is a ways away from them so it does not contribute to side load holding, so I felt safe in taking it off on ours. The top leaf/front eye does most of that with the shackles taking the rest.
One thing that I forgot to mention in the last post was that we did, accidentally, do a no air test of our setup when we left a campsite to go to town and I forgot i had let the air out to level us the night before. It didn't hurt anything, or make horrible noises, but I could feel that the rear had quite low travel to it and very highly damped. It was at reasonable, but low, height. It was not nearly as easy to drive that way compared to with air in the bags.
In Bob's case, because of the towing, he may actually want more rate than we have as he is dealing with a lot of momentum that we don't have. I have a feeling that he might start to get too much rear motion based on what I feel in ours, which is probably close to getting where some people would think it is too much motion. Of course, most air ride systems give very similar feelings, so nothing different there, I think.
My best guess for what might be a good solution with the trailer would be to remove the overload and replace with a full time load carry leaf of maybe 1/2 of the capacity of the overload leaf. That would give him higher rate than we have to handle the extra mass he has, while getting rid of the problem of the overload spring coming in and out of play very harshly. I think that would smooth out the travel of the rear suspension without making it too soft.
In expanding it a bit further, it would probably also be what I would do with a 210 that has higher rear weight and the longer overhand in the back.
Here is the only link I could find with a couple user reviews of the R4Tech, which indicates the system did not sell very well. Sounds like the system had good potential but there were issues, including poor support from Firestone.
Here is the only link I could find with a couple user reviews of the R4Tech, which indicates the system did not sell very well. Sounds like the system had good potential but there were issues, including poor support from Firestone.
Thanks, Pete, very interesting read, if you ignore the grumpy characters on there!
Way fancier than we have, or need I think, but seemed like it would have potential, especially for those the put the big weight of a trailer on and off. Less benefit, probably, for those of us with much more consistent weight.
In the big picture, there really isn't anything special about doing the spring plus bag, as that is what adding all airbags to stock setups is, too. All that is changing by removing the overload, or replacing with a full time, leaf is the linearity of the spring rate increase and smoothness of the transition of weight to different areas.
I am beginning to believe more and more that Bob might get good benfits from and relatively minor rear spring change to something more linear in springrate and of capacity able to better help control his momentum without the impact of hitting and overload leaf.
I looked under both the 2004 and 2013 RTs. Both have what look to be the same six leaf springs. In both cases the overload springs are in contact with the next leaf above them through thin circular rubber pads at both front and back ends of the overload springs.
I can not see a difference in spring contour, no inversion of the older springs and no better arch of the newer RT rear springs.
This is making me think the air bag internal bounce stop may be playing a role somehow.
I still need to talk with the RT specially shop in Gainesville to see if custolmer who have traded to newer Chevy RT 190s have mentioned more bounce in rear springs and to ask if that shops delivery driver has noticed any difference in newer vs old Chevy RT rear end hop.
I looked under both the 2004 and 2013 RTs. Both have what look to be the same six leaf springs. In both cases the overload springs are in contact with the next leaf above them through thin circular rubber pads at both front and back ends of the overload springs.
I can not see a difference in spring contour, no inversion of the older springs and no better arch of the newer RT rear springs.
This is making me think the air bag internal bounce stop may be playing a role somehow.
I still need to talk with the RT specially shop in Gainesville to see if custolmer who have traded to newer Chevy RT 190s have mentioned more bounce in rear springs and to ask if that shops delivery driver has noticed any difference in newer vs old Chevy RT rear end hop.
On the newer model with the airbags are you seeing the springs in contact with the overloads with the rear at normal ride to match or be about 1" higher than the front? Most of those that we have heard about, and ours, would be in the range of 1/8" or a bit more off the pad in the front of the overload, usually at about 30-40psi? The "pad" is actually metal AFAIK and will make a very hard stop.
It is also possible that with the trailer momentum that it could be lifting the rear off of the overload when you have the airbags also helping do the same, although you said you saw the same issue with no air in the bags.
Air bags inflated to 45 PSI gave 1/4 " clearnce at end of overload springs without the trailer.
At 90 PSI I measured about 3/4" clearance betwen overliad spring and the rest of the springs both front and rear, again.no trailer.
Yes the rear end hop seems equally noticeable with or without the trailer and seems present with 5, 50 and 90 PSI.
The pad at the end of the overload springs on my 20013 was flexible but very thin so no good for shock absorption.
Air bags inflated to 45 PSI gave 1/4 " clearnce at end of overload springs without the trailer.
At 90 PSI I measured about 3/4" clearance betwen overliad spring and the rest of the springs both front and rear, again.no trailer.
Yes the rear end hop seems equally noticeable with or without the trailer and seems present with 5, 50 and 90 PSI.
The pad at the end of the overload springs on my 20013 was flexible but very thin so no good for shock absorption.
Those measurements look to be very typical of what we have heard about and seen at those bag pressures. With that much increase over no air, you should be up quite ways off the internal bumper. IIRC, when I tested it on the bench before I put ours in, it would first contact the bump stop over an inch lower than max bag height.
Do you happen to recall how far off the overload you are with the trailer on?
Bob,
Maybe I missed it, but do you use an equalizer hitch? I ask because I just saw this article discussing issues with air bags and equalizer hitch use.
Yes I do use an Equalizer Hitch - the rig seems to handle better with it although this trailer handles pretty good compared to several others I own - probably in part due to smaller overall side "sail" area.
Thanks for the Equalizer Hitch - air bag link
Pete,
After going through the video I agree with the physics represented by the two presenters.
The weight distribution and anti sway features of the Equalizer Hitch essentially transfer excess tongue weight trough the truck frame to the front axle and back through the trailer frame to the trailer rear axles thereby decreasing the effective weight on the truck rear axle and restoring what would be under weight load on the truck front axle
Having too little weight on the front axle should cause handing issues so a properly adjusted weight distribution hitch makes a big difference.
Mt RT with the 4" raised front axle as a result of the Moog springs leaves the RT quite tail low without the trailer so adding air to the bags to get the RT back to level then hooking up the trailer and adjusting the weight distribution hitch, as recommended in the video makes sense to me and is what I do.
Essentially I get the RT level with air bags, then add the trailer tongue weight, then redistribute the tongue weight off of the RT rear axle and back onto the front axle and trailer axles.
That was probably the best visual presentation that I have run across.
BTW, I can get the weight measurements with and without weight distribution hitch connected in one trip at most commercial CAT scales by putting both vehicle axles and the trailer axles on three separate scale pads for the first measurement then disconnecting the trailer and putting the tow vehicle axles on two separate pads, the trailer tongue jack (disconnected from the truck) on another pad and the trailer axles on a fourth pad.
Pete, Bob, perfect timing on that article and your inputs, for me anyway.
I have been reading about equalization hitches and setting, tongue weights, etc and have come to the conclusion that little of it makes sense to me from a pure "where is the weight" point of view.
I have seen so many idea of getting tongue weights, from bath scales to tongue scales and such, but where I lose it in what happens when everything is hooked up.
What I saw absolutely nowhere, is exactly where I think you would need to start as it is fundamental to the trailer load capacity rating. I would think that what you would really need to measure, simultaneously, would be the tongue weight and the weight on each of the trailer axles so you know that you don't have too much weight on one of the axles, which I think would cause rotation around around that one heavy axle. Talk of getting tongue weight then hooking up and either with bars or or bags would change the weight one each axle and also change the weight on the hitch.
I think the nicest thing I saw was a hitch that had a scale built in, so you could set your tongue weight with everything at ride height where you want it, presumably the normal or slightly down from stock height, I think, and with the front pulled down with the bars. You would know about if the tow vehicle is where it was by height so have an idea of what each end is carrying, you know the hitch weight exactly, and then you could get axle weights on the trailer to confirm not unbalanced on the axles. The hitch scale wasn't even all that expensive IIRC.
If Bob is 4" up in the front on the springs he has to have springs that are much higher rate than the rest of us got with similar speced ones, where the norm was more like 2" or a bit less even. That includes the early 81004 MOOGs that have been used quite a bit. Only the last year or so are we hearing of the much higher lift from them. They are going to be very hard to push down with the bars, I would think. I would also think that if he raises the back to match, or close, he is going to raise the tongue that much too, unless he uses an drop hitch of the same amount, or he is going to unload the front trailer axle and load the rear, and put more on the hitch otherwise.
I would think that if the axles were equally loaded, a two axle trailer should be quite low on porpoising compared to if one axle is loaded higher.
Perhaps it is a combination of the very much stiffer and higher front springs with trailer balance not being the same as it was when actually in running height. If the hitch is higher and front springs higher and stiffer, it may be that the middle is the only place left to bend so the rear bounces more than than the equalization hitch can redistribute.
This may also be why some are recommending no air bags with equalization hitches because it is too easy to move them to be fighting each other rather than each doing what they should.
Of course this is all conjecture, and could easily be way off, but when you look at things that changed with the new parts, front stiffness and height and rear height bounce right to front of the list, I think.
This is a tentative update on my 2013 Chevy Roadtrek 190 rear end vertical "hop".
I removed the air bags and drove my test equipment (wife) around sitting and reclining on the rear bed/seat area - both of us think it rides like our 2004 Chevy RT 190.
The proof will be when I tow our aircraft trailer over a couple of hundred mile trip. If the tools hanging on the front walls of the trailer remain in place I will know that the cause is associated with the air bags.
Pete, your tip on installing large pressure tanks connected to the air bag lines to allow greater volume for air compression starts to look like it may be the following step.
This is a tentative update on my 2013 Chevy Roadtrek 190 rear end vertical "hop".
I removed the air bags and drove my test equipment (wife) around sitting and reclining on the rear bed/seat area - both of us think it rides like our 2004 Chevy RT 190.
The proof will be when I tow our aircraft trailer over a couple of hundred mile trip. If the tools hanging on the front walls of the trailer remain in place I will know that the cause is associated with the air bags.
Pete, your tip on installing large pressure tanks connected to the air bag lines to allow greater volume for air compression starts to look like it may be the following step.
More when I get to these.
BJ 2004 and 2013 RT 190 Pops Fl Keys
Thanks Bob, more good information and kind expected based on your 2004.
I think this is telling us that to get what you are looking for, you need the very high spring rate of the overload leafs as when you take the bags out that is what you are running. The bags will soften the ride and lower the springrate substantially, especially the higher up off the overload you go with the bag pressure.
For the above reason, I think adding a surge or extra capacity tank may be the backwards way to go, as it will likely reduce the spring brate of the airbags and make things more bouncy.
Now that the bags are out of the way, a relatively low cost and effort test might be to find some of the right height for the lift and stiff Timbren style urethane bump stops to put in. They tend to be much higher rate than the airbags and may do what you are looking for. I saw some at a local shop last year that were very large and firm for pickups. The other option would be to get taller rear springs that would match the spring rate you are getting with the overload in place on your current system, but as a normal pack.
On edit, there is also another thing that you could do, I think.
Since you have a 190 as I recall, it would have come from the factory without any lift blocks in it like they put on the 210s with more overhang and rear weight. Since you probably will get the ride you want when sitting on the overload leafs, you could just put in 2" blocks to get the lift you want. The blocks go under the springs, so the springs should function the same before and after adding the blocks. At a minimum, it would tell you if it is height or spring rate giving you the issue.
I removed the air bags and drove my test equipment (wife) around sitting and reclining on the rear bed/seat area - both of us think it rides like our 2004 Chevy RT 190.
BJ 2004 and 2013 RT 190 Pops Fl Keys
Did your "test equipment" do a test ride in back when the airbags were installed?
This discussion has me wondering about the engineering design aspects of suspension systems. One of Akin’s design of spacecraft laws came to mind: “Engineering is done with numbers. Analysis without numbers is only an opinion.”
Now this “law” overlooks a key effective means of engineering design; that is that experience in designing systems can also work well, where design knowledge is based on past experience. As you try different things you learn by experience what works and what doesn’t. Knowledge of the “physics” of the system, with associated engineering numbers, along with experience should yield the best capability to design an effective suspension system.
It would seem that some basic characteristics of springs would be helpful, like:
1. What are the spring rates for the stock setup. These will vary with load as the overload springs will increase the spring rate when they come into play.
2. Then with airbags, what is the effective spring rate. And how does the spring rate change as a function of additional volume.
3. Then what about Airlift’s bags with internal jounce bumper: what is the spring rate on those. Is it possible this jounce bumper is introducing more spring rate than desired (I think this has been mentioned before)?
4. How do the shocks and their characteristics enter into the suspension design equation. I assume they have an effective spring rate that is a function of how rapidly they are compressed, though their primary purpose is to damp out oscillatory motion on the rebound.
I would think (hope) that Airlift has the engineering expertise to put all these pieces together. Perhaps, in most cases, just adding airbags works. But we may have a special situation here with our heavily loaded Roadtreks. In the past I have inquired of a companies engineering department and, on occasion, found the right person that was knowledgeable and interested in my problem and worked with me to resolve my issues. Perhaps some calls to Airlift may get you in touch with the right engineering department folks to help. It is worth a try.
Linear Mode
