Chevy Suspension Upgrade Complete

[Bjones7788]

I installed the Moog 81004 front springs, Air Lift 5,000 rear air bags and Bilstien shocks all around last spring with maybe 15,000 miles of driving and towing on the set up now.

The additional ground clearance after owning RT 190s for well over 250,000 miles is absolutely worth it. I no longer have to deliver a pile of 2 X 8 planks to shops to use when driving this RT up on the shop lifts in order to get enough clearance to avoid risking damaging the bowels of the RT. No more fear of unmarked non-standard speed bumps ripping holding tanks lose, etc.

Question: I get a more pronounced vertical bounce in the rear of this RT after the installation than before the installation, with the air bags at 5, 50 or 100 psi.

Initially this was just an impression. But, I frequently tow a 7,000 pound enclosed tandem axle trailer coast to coast with delicate cargo and find the stuff hanging on screws along the walls in the front of the trailer bounces off all of the time now, which had not happen going across the country on numerous trips before. The rear bounce occurs with and without the trailer and regardless of the amount of air bag inflation

So my question is 1. Why? And 2. Any thoughts on a solution? I worry about the delicate and expensive cargo.

My old time shop guys suggest the rear Bilstiens are stiffer than OEM shocks and may be the cause so I could try OEM rear shocks again. Any thoughts on that?

Another thought in my mind is that the internal bump stops in the air bags may be more "springy" than the OEM bump stops. Any thoughts on that?

Oh, I got a little more ground clearance all around with my installation than others reported with the same air bags, springs and shocks - which I thought might be noteworthy.

BJ
2003 RT 200, 2004 RT 190, 2013 RT 190 and 15 trailers as well as more tow vehicles over 50 years than I can remember
freedog7788@gmail.com 443-480-1023

[booster]

Originally Posted by Bjones7788

I installed the Moog 81004 front springs, Air Lift 5,000 rear air bags and Bilstien shocks all around last spring with maybe 15,000 miles of driving and towing on the set up now.

The additional ground clearance after owning RT 190s for well over 250,000 miles is absolutely worth it. I no longer have to deliver a pile of 2 X 8 planks to shops to use when driving this RT up on the shop lifts in order to get enough clearance to avoid risking damaging the bowels of the RT. No more fear of unmarked non-standard speed bumps ripping holding tanks lose, etc.

Question: I get a more pronounced vertical bounce in the rear of this RT after the installation than before the installation, with the air bags at 5, 50 or 100 psi.

Initially this was just an impression. But, I frequently tow a 7,000 pound enclosed tandem axle trailer coast to coast with delicate cargo and find the stuff hanging on screws along the walls in the front of the trailer bounces off all of the time now, which had not happen going across the country on numerous trips before. The rear bounce occurs with and without the trailer and regardless of the amount of air bag inflation

So my question is 1. Why? And 2. Any thoughts on a solution? I worry about the delicate and expensive cargo.

My old time shop guys suggest the rear Bilstiens are stiffer than OEM shocks and may be the cause so I could try OEM rear shocks again. Any thoughts on that?

Another thought in my mind is that the internal bump stops in the air bags may be more "springy" than the OEM bump stops. Any thoughts on that?

Oh, I got a little more ground clearance all around with my installation than others reported with the same air bags, springs and shocks - which I thought might be noteworthy.

BJ
2003 RT 200, 2004 RT 190, 2013 RT 190 and 15 trailers as well as more tow vehicles over 50 years than I can remember
freedog7788@gmail.com 443-480-1023

Is the perceived bounce with the big trailer on, off, or both?

[peteco]

Booster: Bob indicated: "The rear bounce occurs with and without the trailer and regardless of the amount of air bag inflation"

Bob, you may have ventured further into an area no one has really gone before with a trailer carrying noticeably sensitive cargo.

I have had Bilstein shocks and Firestone 3500-lb airbags on my 2006 RT210P for 9 years now. It rides a little stiffer than stock, but I have not noticed any major bounce issues. I occasionally tow a 4000-lb trailer/boat with no problems that I have noticed. I chose the Firestones because I thought 3500-lb was all I needed and the Airlifts might give a harsher ride with their higher 5000-lb capacity. But I may be all wrong about that. Not sure how the Firestones compare with the Airlifts on size and associated spring rate. My understanding is that a larger diameter airbag will have a lower spring rate than a smaller airbag that needs higher pressure to lift the same load. That may be one area to investigate.

It would help to understand the Air-lift internal jounce bumper characteristics. Perhaps a call to Air-lift would help.

https://www.airliftcompany.com/workshop/jounce-bumper/

Regarding shocks, I had Rancho RS9000 variable damping shocks (not “air shocks”) on an F350 that I used to tow a 10,000-lb 5th-wheel. I had a remote pump to vary the pressure in the shock, which varied the damping. I would increase the pressure with the 5th-wheel hooked up. It towed better with less bounce, and I could not tell if there was any effect on the trailer, though I assume it was probably harsher on the trailer. Generally I was pleased with the shocks, though the adjustment feature failed at 8 years age. Rancho sent me a new set free. I did not have airbags on the truck.

I was curious and did quick search for an air receiver hitch, which is frequently used on heavy 5th-wheel trailers. Here is one for a conventional receiver hitch.

https://shockerhitch.com/products/sh...eceiver-hitch/

Did you get your parts from a suspension site like sdstrucksprings? If so, I would talk to them about your setup and see what they recommend. Or try to find a suspension shop that works on pickup trucks hauling campers.

Sorry you are having problems. We met at Oshkosh in 2017 so I realize you important your cargo is to be handled with care. Unfortunately sometimes upgrades end up needing additional “engineering” to get all the parts to work together to provide a total system solution.

[booster]

Thanks, Pete, missed that comment.



I thought that would be the case, though, as it makes sense.


My guess is that what doesn't really bother most of us, and might actually be a desired thing, is that the rear air bags most likely are reducing the rear spring rate a bit, especially on big bumps. Motion in the back isn't all the bad a thing if it is smooth and slow, which we fount out after I actually removed the overload leaf in the rear, allowing the axle to move further in compression direction. My guess is that Bob is seeing less rate in the back and is bouncing off the overload leaf. It is probable it is hitting the overload and the internal bump stop in the bag at the same time. We saw this with ours on those totally irritating short bridge transitions which would cause a huge "bang" from the rear before I removed the leaf. The softer rate would give the mass much more momentum to hit the over load so a harder bottom out. He probably was on the overload all the time before so no slamming into it.


The other thing that may be going on is that the front has been increased in springrate and likely in damping rate, which will tend to limit it's motion to a degree. If you hold the front more solidly, especially with a trailer, the rear has to move more, accentuating the issue.


I think as a first guess is that Bob would need higher spring rate springs in the rear to smooth the transitions out without hitting a huge leaf suddenly. More of a higher rate, more linear, motion to smooth out the motions. If the springs are selected to handle the lift/load of the van without the trailer relatively smoothly, then the 5000# bags can be used to pick up the trailer increased load.



I would assume at those weights of trailer, he is using an equalization hitch, so that can also be a big factor in rear bounce and may need some tweaking in setting to match the new springrates and damping of the different parts. He is going from a van that was likely sitting on the very high rate overload leafs in the back, and the beehive bump overloads in the front so a lot of things have changed.


Airlift are 5000# bags, Firestone are 3500# bags, IIRC.

[Bjones7788]

Originally Posted by booster

Is the perceived bounce with the big trailer on, off, or both?

Booster, Yes, bounce is present with and without the trailer, and it seems to be present with 5, 50 or 100 PSI in the air bags, although probably more prominent with higher PSIs.

Thanks for thinking thru this concern.

BJ

[Bjones7788]

The rear Bilstiens have been removed on our 2013 RT 190 in exchange for NAPA Reflex Truck Shocks which are supposed to be close to OEM in performance.

After I recently swapped out the OEM rear shocks for Bilstiens in our 2012 RT 190, the rear ride seemed a bit harsher but acceptable, however, a lot of the stuff hanging on hooks in the front of my toy hauler trailer all of a sudden started bouncing off of their hooks, even of relatively short trips. Historically I could drive coast to coast without any tools and stuff bouncing lose.

I carry a plane in this trailer, so I need a gentle ride that does not beat the plane up.

If this "down grade" helps, I will report back.

By the way, The Bilstiens all around were part of the Moog front springs and rear air bag lift conversion, which I really like because of the increased ground clearance.

I hope to report back after the next long trip.

BJ 2004 & 2013 RT 190 Pops (currently)

[booster]

Thanks, BJ good information.


An odd question came to mind when you have the trailer on.


Have you had it on the scales to see what the van axle weights are with the new parts and with trailer fully loaded and in place?


I ask because I have run across a few times where with an equalization hitch, people have changed stuff in the tow vehicle similar to what you did and had some issues because the hitch wasn't readjusted to work right with new parts. Porpoising was one, but rear oscillation also. I think it was because the hitch weight changed too much.


You mentioned being a bit higher than others have seen with Moog front springs, which seems to be common in the last 3-4 units. What front height to the wheel lip did you wind up with?

[Bjones7788]

Pete, Booster,

I really appreciate your time.

The perception of rear hop or bounce is minor and pretty much dismissable from my position as driver as an unconfirmed impression attributable to stiffer suspension.

The fact that tools and such had remained hanging on the walls in the front of the trailer previously had quite frankly amazed me, however when I noticed that stuff was hopping off and ending up on the trailer floor it caught my attention. Had I not started seeing the tools on the floor I would have ignored it as inconsequential.

Pete, The interaction of stiffer front springs, transferring more energy to vertical movement at the hitch ball had not occurred to me, but the connection seems plausible.

A call to an old timer at Air Lift 5,000 technical support makes sense, in terms of the internal bump stops possibly increasing rear end "bounce".

Booster, I don't have CAT scale weights on the rig after the conversions, and I will get that done thoughtfully, capturing tongue weight and all RT & trailer axle weights with and without the load leveler hitch, plus I will re-work the hitch setup directions. Wise ideas after the conversion.

I tend to operate close to 15% of loaded trailer weight on the tongue and tend to accrue weight in the trailer with time, so I know I have to check weight and balance frequently and in the past have detected measurable weight transfer to the front axles of the RT with the Equalizer hitch I currently favor.

To answer Booster's question, I got a tad over 4" lift at the front wheel spindles of the RT based on before and after Moog spring installation - somewhat more than I expected (Without the trailer connected of course)

Pete, Yes the springs and air bags came from a shop specializing in them - good suggestion to chat with their tech folks. And, thanks for the hitch air bag reference.

I suspect (hope?) that less stiff rear shocks (just installed) will minimize the bounce or hop transferred from the rear of the RT to the front of the trailer.

Again, I appreciate your advice and time.

BJ

[booster]

Do you recall what the actual wheel lip dimension is now. In the early versions with the 81004, IIRC lift was in the range of 2", or even a bit less, and lip height at about 35.5" with stock tire size.

[Bjones7788]

Booster
The pavement to front fender height was very close to 32 3/8" left front and 33" right front before Moog 81004s and 36.5 left front and 37.25 right front afterwards on the 2013 RT 190 Pop, that is a tad over 4" of lift - The conversion and measurements were done March 2019 with maybe 40,000 miles on the vehicle at that time.

The 2004 is here also so I measured it. OEM suspension measures about 32" left and right front at this time.

BJ

[Bjones7788]

Booster,
I am pretty confident that my Moog 81004s had the spring material the ends cut off at a tapper rather than squarely across the diameter of the coiled metal rod.
And, I did measure the height of the coil because some folks were receiving taller coils and the length was what was called for (17.5"??) plus I measured the diameter (with electronic caliper) of the rod material before installation. As I recall the diameter was the narrower of two discussed in the threads on this conversion. So I was a bit surprised to get 4" of front end lift.
BJ

[booster]

Originally Posted by Bjones7788

Booster,
I am pretty confident that my Moog 81004s had the spring material the ends cut off at a tapper rather than squarely across the diameter of the coiled metal rod.
And, I did measure the height of the coil because some folks were receiving taller coils and the length was what was called for (17.5"??) plus I measured the diameter (with electronic caliper) of the rod material before installation. As I recall the diameter was the narrower of two discussed in the threads on this conversion. So I was a bit surprised to get 4" of front end lift.
BJ

Thanks BJ. The original springs had a wire size of 1.03" and a free height of 17.75". We have speculated over the last few installs as to why they are now giving much more height. Most had one end closed and the other slightly open, but no grinding flat on the ends. The lower control arm pocket is indexed for a non ground spring so a flat one would not fit correctly. The top mount is flat so either would work there.



Most of the vans start at about 33.5" at the wheel lip, so 4" would give 37.5". I tested a set of Erb springs that gave nearly 38" of lip height and they were not good for handling or ride. Going that high gave very noticeable bump steer and made getting decent caster impossible on our van. I took them back out immediately. They also were so high that the front shocks were not long enough unless the mount was move to the top of the lower control arm from the bottom as they were very near topped out all the time. Just looking the suspension, it appears that it is likely the anything much over 2.5-3.0" of lift (36-36.5" lip height) would start to mess up the geometry quite a bit. The factory "trim" height in the service manual for a 3500 van gives a lip height of about 35.75" on stock tires.

[Bjones7788]

Booster,
Thanks
And I am saving your comments to work from.
I will almost certainly change the front shock mounting to the upper side of the control arm, talk with the shop that did the alignment - which I had not done - and look into the bump steer issue.
I am not experienced or trained in springs but since my spring wire diameter and length seemed to be to spec I would have guessed the unexpected height to be a matter of metallurgy/treatment resulting in a stiffer spring??? Comments welcome on that.

Pete re: Oshkosh reference - AOPA LIVE weekly online video magazine put us in their end of year "Directors Cut" edition as one of their best stories of 2019 along with flying with the Air Force Thunderbirds and an Alaska TV star flying a Super Cub on floats - quite a neat holiday surprise for us.
BJ

[booster]

It will be interesting to see what all you find out.


Yes, normally we would consider springs of same diameter wire and free length to be equivalent and give the same ride height. Beyond that, the only other real things that can change the rate and thus finished height or the material and/or heat treating and the wind angle/number of coils. Others have mentioned the coil count to be the same as all the others, so that only leaves material and heat treat, I think.


It would be interesting to see what the actual rate of the springs are on a spring rate tester, but those are nearly impossible to find and get it done.

[hbn7hj]

Would like to note that the front fender well dimension has settled to 36.5” left and right from over 37” left and right on initial installation of the Moog 81004 springs last spring. Just an FYI.

[booster]

Originally Posted by hbn7hj

Would like to note that the front fender well dimension has settled to 36.5” left and right from over 37” left and right on initial installation of the Moog 81004 springs last spring. Just an FYI.

That actually is quite a bit compared to others. Has it stabilized at this point?

[hbn7hj]

Only measured it this one time. Will do so every so often.

[peteco]

Bob,
While pondering your situation I did a little poking around and found several articles on the subject of airbag harshness and the use of “ping tanks” as a solution. Basically the ping tanks adds air volume to the system so when the bags compress on a bump, the pressure increase is not as large as when there are no ping tanks. This effectively reduces the airbag spring rate. You might want to start asking around to area suspension shops to see if any are knowledgeable on ping tanks (or other possible solutions).

https://forums.goodsamclub.com/index...pging/1/page/1

Add 'Ping' Tank to camper air bags


Hope this helps,
Pete

[booster]

Originally Posted by peteco

Bob,
While pondering your situation I did a little poking around and found several articles on the subject of airbag harshness and the use of “ping tanks” as a solution. Basically the ping tanks adds air volume to the system so when the bags compress on a bump, the pressure increase is not as large as when there are no ping tanks. This effectively reduces the airbag spring rate. You might want to start asking around to area suspension shops to see if any are knowledgeable on ping tanks (or other possible solutions).

https://forums.goodsamclub.com/index...pging/1/page/1

Add 'Ping' Tank to camper air bags


Hope this helps,
Pete

Never heard it as that term, but have in heard of it in lots of applications, including vehicles. If you increase the volume with all other things equal, you do reduce the rate of pressure climb which is springrate too.


Our experience with our Chevy 190P Roadtrek would indicate that if you have the Airlift bags, you would not want to add anything to lower the springrate if you are still using the overload leaf in the spring, and maybe not if the overload is still there.


What we have found that makes me say this is that I removed our overload leaf from our Chevy so it the is no longer any really high springrate kicking in on moderate to large bumps, airbags or not. The ride quality changed quite a bit, getting much smoother on especially the big dips and those horrible bridge transitions in some states. Of course there are always tradeoffs, and in this case is that we do get more motion in the rear as it is overall a softer sprung. It is bigger, but slow, travel so not any kind of issue for handling or pitching, but you can feel it. The Bisteins pretty much make it one and done oscillation, though. I don't think I would want to go a whole lot softer than this as it might get into porpoising on dips unless running higher bag pressure. We are currently at about 40-50 psi.


I think adding the extra tank of for volume may make for a better ride on those that are using the bags for lift and clearance and running higher pressures than they need for control and handling.

[peteco]

Originally Posted by booster

Our experience with our Chevy 190P Roadtrek would indicate that if you have the Airlift bags, you would not want to add anything to lower the springrate if you are still using the overload leaf in the spring, and maybe not if the overload is still there.


What we have found that makes me say this is that I removed our overload leaf from our Chevy so it the is no longer any really high springrate kicking in on moderate to large bumps, airbags or not. The ride quality changed quite a bit, getting much smoother on especially the big dips and those horrible bridge transitions in some states. Of course there are always tradeoffs, and in this case is that we do get more motion in the rear as it is overall a softer sprung. It is bigger, but slow, travel so not any kind of issue for handling or pitching, but you can feel it. The Bisteins pretty much make it one and done oscillation, though. I don't think I would want to go a whole lot softer than this as it might get into porpoising on dips unless running higher bag pressure. We are currently at about 40-50 psi.


I think adding the extra tank of for volume may make for a better ride on those that are using the bags for lift and clearance and running higher pressures than they need for control and handling.

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.