Must replace helper springs....what's best?

[TexasExcursion]

I had a set of helper springs installed on my X last summer; however, recently the dealership told me that the springs are rubbing on the emergency brake and the body on the drivers side, and rubbing on the body and the cooling lines (will puncture them soon) on the pass side. I called the shop that installed them, and they told me that this is a problem on the X's and there really isn't anything that can be done. (The springs were installed in El Paso, TX and I've been transferred to Mass, so I'm not pursuing the issue with the shop).

I'm pulling a heavy trailer--11k--and need something on the rear end. There are many posts on this forum giving all sorts of advice, but I haven't been able to figure out what's best for my situation. I don't want to lift the truck, just help out the rear end.

Air bags? Something else? Manufacturers? Let me know what you think. Please include a ballpark $$$ figure because if the cost is too high, I've got to account for the cost of a divorce in the final price. [img]/ubbthreads/images/graemlins/eek.gif[/img]

Thanks in advance,
Bruce

[FamilyRide]

The #2 top options by popularity are Air Bags ($300 or so) or Timbrens. I think the Timbrens would most duplicate what you have with overload/helper springs as are cheaper (not sure how much though).

[boatpuller]

Personally, I'd like you to get the airbags, and then compare and contrast how they work vs. helper springs.

I've got airbags, and also had them on the prior truck. As it's my daily driver, being able to reduce the air when it's not pulling is nice. But, some claim when the bags are inflated over 50 psi (about 2500lbs of extra boost) the ride gets bouncy. I run 9 position rancho's and tighten them up for those loads.

But, it be nice to hear from someone who's had both.

[Bruce1954]

[ QUOTE ]
The #2 top options by popularity are Air Bags ($300 or so) or Timbrens. I think the Timbrens would most duplicate what you have with overload/helper springs as are cheaper (not sure how much though).

[/ QUOTE ]

Timbrens may be ok for heavy loads all the time but I think you would find them very stiff. If you go to the timbren site find the recomended kit number look up the "spring" used then go to the spring data chart you will find the spring rates are way up there.

I Just looked Kit # FREXC4 uses Spring # A535-65
Max Def is 2.375" with a max bump capacity of 11000# so 11,000/2.375 = 4842#/inch IF I am reading this correctly that is over 10 time the rate of the OE spring of 410#/inch. This is all per spring.

I need to order bags As I have a heavy duty trip to make and I know I will be dragging my rear again. I think I will go with the Air-lifts and add two extra resiviors with 1/2 tube between the air bags and the reserviors so that the spring rate remains much more constant over say a 2" stoke or bump.

When I figure this Out I will post details.

BTW I have hauled over 11K with nothing but good shocks in back and it does not sit as low as when I add the family and the adda-trunk.

Bruce

[sail684]

I really disliked the airbags on mine. Pulled them off and sold them. Replaced the rear springs on my 4x2 Ex with the rear springs from a 4x4 F350 that I got from a lift shop. I love the ride and handles the trailer load really well.

[DOC4444]

Hi Bruce,

Is this extra air cannisters idea something that you know from some source will work? The Airlift Super Dutys do the job, but should really be thought of as adjustable bump stops. They effectively can't be used to adjust ride height, just load capacity. If you pump them up just a fraction too much, it feels like the rear axle was just welded to the frame. I assume your idea is to try to "soften" them a bit to minimize the aforementioned problem.

I'm just not sure that 2 extra standard resevoirs will do anything. I have a feeling that that some sort of "semi-rigid" resevoir would be needed. It would have to be able to hold, say, at least 40 psi, static, but would also "give" (expand) a bit when the bags are collapsed by bumps.

DC

[Bruce1954]

Doc

I have a little background, I had a set of firestones on my E150 it was the only way to hold it up in the back as it was a full converstion and weighed in at a little over 6000 empty with a gvw of 6400 so it was out of wack.

I know we traveled at over 8000# in it it I had the bags inside the coils in the front also, wish I had know about rancho adjustables I never could control the rebound in the back with or without air bags.

The problem with bags is the spring rate changes very fast as the air is compressed our metal springs are constant rate. I don't remember the formulas exactly but as I recall assuming no temp change if you reduce the volume buy say 40% you increase pressure and stiffness by 40%.

I believe if you had a large enough connection to a very large tank or resivior then the pressure in the bag does not change and hence the pressure on the axle in constant and only compensates for the additional load.

I did some of this on my van but I also put flow controls in the air lines between the bags and the resivior so that the air could go out quickly but refills the bag more slowly just like a shock. It did help but I never could controle the rear end. I tried several high end rear shocks and you are not going to believe this but the best was the OE ford shock! I put new ones on about every 40K.

I have a set of Air LIfts comming from Summit, I found them for about $10 less but having bought form summit prior I went with them. Never could figure out why the kit for the 2x4 X was about $50 less.

I was going to look tonight and see if I could estimate the volume of the bags so that I can figure a resivior about four times the size of the bag.

I want to re-port the bags to 3/8 or 1/2 inch to the resivior then I can use the standard hardware to fill the resiviors.

I had a compressor in the van and it was nice I used pressure regulators to hold the pressure in the front and rear. I may put one in the X also but not now.

[Texcursion]

I did the same. Found a truck accessory shop that put a lift on a F350 and bought those springs cheap. I didn't use the overload spring but instead installed the factory lower bushing bar (or whatever it is called). That plus adjustable shocks for when I pull our 10Klb RV and I haven't looked back.

[DOC4444]

Hi Bruce,

That was my main point, that the spring rate of the bag goes to infinity in a nanosecond (hence, the "adjustable bump stop" reference). Though air can certainly be compressed, with the setup I think you are contemplating, I don't think the air can effectively be compressed enough to do what you want, even if the volume is increased tenfold.

Since the bags themselves hardly stretch, something else has to give in order to achieve even a progressive rate. Seems to me we need an external cannister with a constant rate coil spring in it with the "right" rate and a diaphram. That way, the airbags, connected to this cannister, would have close to a constant rate. As you add air, you would just increase load capacity, not spring rate. This would also allow what we can't do now, which is to raise ride height without increasing spring rate.

At some point, as you increase air pressure, the spring in the cannister would go into coil bind, sending the spring rate to infinity. However, with the right size, volume and spring rate, it would cover loads over the full appropriate range for the vehicle.

I had a Windstar minivan with Ford factory "self-leveling" rear suspension. It worked on the above principle and performed wonderfully.

Also, I don't understand the idea of slowing the "return rate" of air to the bags. Unless you only hit bumps that are spaced out significantly in time, it would seem that the bags would tend to stay somewhat collapsed, minimizing their effectiveness and with a heavy load on board, lowering ride height.

This would be a version of what the NASCAR boys used to do before the tech guys caught on. To get around minimum ride height rules, they used shocks with so much rebound damping that the suspension would "jack down" to the bump rubbers at speed, but being slowly pushed through the tech line would pass over the blocks fine.

NASCAR fought this by making everyone use the same "spec" shocks, literally handed to them just before the race. The teams fought back by using really soft coil springs so that the downforce was enough to collapse the suspension to the bump rubbers. (Horrible for the drivers. Made the cars into gokarts.) Now NASCAR provides the springs as well.

DC

[Bruce1954]

Doc I think you may be getting way to complicated but I am interested in exploring an air bag adjustable rear end for the X.
First let me explain why I did the flow control thing on the van, It had a bounce problem even without bags I could never get enough rebound control in the back of that thing so I added rebound control with the flow controls.

Also I do not know of a practical size "near constant rate metal spring" but I think we can come close enough with just air, here are my thoughts, I also think you are on the right track and we agree with what we wish to accomplish.

We made a trip from Asheville to Chapel Hill and back today so I had some time to think about our subject.
So here goes my theories:

I think it possible to lift the X a bit and soften the ride, not sure if the numbers will work out to make it practical but I think so.
I will have to do a little research and calculations to figure it out.

I learned a long time ago that if I was not sure about a theory take it to the extremes if it holds at both ends then it is likely to work in the practical middle so here goes.


For starters our G code rear springs are 410# per inch so at a light load of say 4000# in the rear you first must subtract the rear axle weight of about 750# so now you are supporting 3250# SO 3250 / 820 = 4" of pre-compression approximately so if we add 810# it goes down an inch, so far this sounds about right.

Now start adding air or additional springs lets assume we want to add 1000#s to the rear axle and hold the height with a very small air spring with only a square inch of effective piston area, I know, not reasonable just go with me here, if we have two springs or pistons with only one square inch each then we have to have 500PSI in each spring if they only had say 2" of additional stroke and you hit a one inch high bump then now the springs have 1000PSI in them so we have added a 1000# per inch spring to the rear, darn stiff when added to the 820#/" we started with.


Now go to the other extreme take a standard Air Lift or Ride Rite kit but add a large dia hose from each bag to say 200 gallon air compressor tank, I know very impractical but we are only testing a theory here, Now if you compress the air bag springs they are almost not a spring at all but a constant rate lifting device since the pressure does not change. Now take it a step further since both Firestone and Air Lift claim they can lift 5000# per pair they should hold the rear of our truck up.

Now do not do this we are only looking at the theory to convince ourselves this is correct.
Imagine disconnecting the rear shocks and removing the rear spring rear shackles so that the truck is sitting just on the bags.
Now those bags are still connected to our infinite size tank so that the pressure does not change with compression of the bags
Now pressurize the system so that the rear floats on the bags, could you not move the rear up and down with almost no effort?
It is at a steady floating pressure if you move it up it stays push down it stays in other words zero spring rate.

So now if this is correct how big would a reservoir have to be so that the spring rate is fairly low or very low and the bags only add lift, exactly what we are looking for.

First we have to look at what we have, going back to our one inch bump with stock springs we have the following:
810# / 32500 = 25% increase in spring pressure from a one inch bump I think that is fairly stiff already and adding more rate with bags only compounds the problem just as you have experienced.

If all the above can be "bought into" then now the engineering begins to lift the X and soften the ride just a bit since we do not want to compromise the safety or handling.

What do you think????


Bruce

[AllAboutJeeps]

[ QUOTE ]
We made a trip from Asheville to Chapel Hill and back today so I had some time to think about our subject.

[/ QUOTE ]

And I thought people talking on cell phones while driving were distracted! With that much going on in your head, I am amazed you found your way home (j/k)! As always, great idea/reading Bruce!

...danny

[Bruce1954]

[ QUOTE ]
[ QUOTE ]
We made a trip from Asheville to Chapel Hill and back today so I had some time to think about our subject.

[/ QUOTE ]

And I thought people talking on cell phones while driving were distracted! With that much going on in your head, I am amazed you found your way home (j/k)! As always, great idea/reading Bruce!

...danny

[/ QUOTE ]

The wife drove to while number two son worked on a scout project on a laptop with me looking on the back seat. The trip home was all up to me however with only the sounds of the two of them sleeping to keep me awake.


Thinking further in one of my other Thinking spots this morning you can not "soften" the ride without changing/lowering the spring rate however I think you can keep from increasing the net spring rate and therefore not make it any stiffer even with a load and that will be what I am looking for.

If I am near empty I and others are not back there anyway it is under load that I would like the smoothest ride, and to stay off the stops in the rear as well.

I will do some more digging tonight and see if I can start the CALCULATIONS.

Does anyone have a bag number for the Air lift system? the one I ordered should be in Tues or Wed anyway.

Bruce

[Bruce1954]

Texas X

Have not given up

Preliminary numbers I ran just guessing at some things said an air bag at 45 PSI doubles the spring rate = Divorce so we dont want to go there

Also looks like a 2 to 3 gallon reservior per spring to get the spring rate near zero, that seems a little big.

Hopfully will do some real calculations tonight also want to call Air lift and see if I can swap bags for some with 1/4 connectors Reporting what I have may not be an option

Anyway I am in the process of the final engineerng prior to install!


Bruce

[TexasExcursion]

Bruce,

I gotta tell ya, my heads been spinning reading all these posts. [img]/ubbthreads/images/graemlins/grin.gif[/img]

The way I see it, I have to remove the helper springs otherwise I'm going to puncture the rear cooling lines--no fun there. Which leaves me with a stock rear end pulling an 11k trailer (will probably be more like 12k when loaded with fluids, etc). Are you saying that if I add rear super duty air lift air bags it'll make the ride rougher than what it is with the helper springs (no load, no trailer)? Because it's pretty rough right now. Based on other posts, I got the impression that air bags with 5 psi would pretty much give a stock ride.

Also, I'm really not tracking on the reservoir stuff. Can you break it down for me? [img]/ubbthreads/images/graemlins/vulnerable.gif[/img]

Bruce

[Bruce1954]

Ride could be should be better than with helpers

I don't know what your helpers did to the spring rate.

My goal is to add capacity without increasing the spring rate to any significant degree.

Bruce