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Old 03-23-2014, 01:33 AM   #1
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Rear suspension options for lifted 2WD

Hello

I have a 2WD 06 SMB DLS E350 Long Body with the Camburg system, BFG AT285 and Detroid Locking Diff. The back is about 1 to 2 inches lower than the front and despite new Bilstains 5100 shocks it's offroad performance is not very good, the front is great and stable but the back is all over.

Questions is, in order to level and stiffen the offroard ride without compromising (perhaps increasing) travel, what's the best option between new springs from Deaver, maybe replace the 2.5 inch lift block with a set of custom springs or just install a set of airbags. Any idea what custom rear Deaver will cost?


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Old 03-23-2014, 11:00 AM   #2
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Re: Rear suspension options for lifted 2WD

I have an EB E350 2wd with Camburg suspension as well. I feel the same way about the ride quality... awesome up front, too stiff in the back. First thing to point out is that it is a 1 ton and will ride MUCH better with, you guessed it, 1 ton of payload inside! I rarely will have more than half that in the back of mine so I am currently investigating spring rates from E250's to see if there is much to be gained with a junkyard set of OEM springs.

At best, that would make the ride a little more tolerable in the rear by using a little more travel for the same hit as compared to the 1 ton springs. If you are looking to make the rear suspension match the front in terms of travel/ plushness, you are going to need to have springs made. The factory springs aren't very progressive at all mostly due to having very few (3+ overload) leafs in the pack, a custom pack will have the ability to start out soft(er) and ramp up to the desired rate as you get deeper into the travel and start engaging more leafs. You really can have the best of both worlds, but it comes at a price. I had talked to Deaver some time ago and got a quote in the $1100 range for custom rear springs that would have 10-11 leafs and 10"-12" travel...not bad for a 15 passenger van!

Adding airbags to raise ride height will require (obviously) adding air pressure, which adds spring rate. That will only make it use even less travel (riding worse) on a given bump and require even more rebound control. The shocks will need some attention no matter which route you take.

I have Fox 2.0's on the front and they are only adequate offroad for lower speeds/ fire roads. A vehicle this size REALLY needs a lot more shock absorber to control the weight, a 2.5" reservoir shock at each corner should be enough to keep things under control at the speeds that one would likely be willing to drive such a behemoth offroad. I only have the Bilstein 5100's on the rear and they don't have anywhere near enough rebound valving. Generally speaking, the stiffer the spring, the more rebound control it will need.

So to sum it up, to make the rear suspension work well you will want custom springs. To make the custom springs work well, you will need better shocks. To make the better shocks work well you will likely have to have them custom valved.

If you are more just concerned with having the van sit level, you can simply swap out the rear block for one of a different height.

On another note: Is your rear axle a full floater? If so, Is your Detroit 32 spline or did you swap in 35 spline shafts?

edit: I found this handy chart with spring rates for the rear, though these ARE NOT OEM: http://www.generalspringkc.com/Leaf_Spr ... s/1891.htm
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Old 03-23-2014, 12:04 PM   #3
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Re: Rear suspension options for lifted 2WD

Quote:
Originally Posted by Nick
the front is great and stable but the back is all over.
What do you mean by "all over"? The stock springs are pretty stiff, but I've never felt them to be unstable. Are they so stiff you are getting bad axle hop?

Generally, more leafs with less spring rate will ride better then less-but-stiffer springs. The worst offender is the lower overload spring, which is something like 750 lbs/in.

I modified my springs by adding a couple leafs from an F350 spring pack. This made the ride much better by keeping the off the overload spring most of the time. I still have to keep that spring though because of the loads I carry sometimes. For most vans however, adding a couple leafs in lieu of the overload spring will make a big improvement.

I did add airbags, but mostly for load-levelling. The help with moderate loads by keeping the van off the overloads. If you run at the same weight all the time however, I think you are better off tuning your leaf-packs for your load.

I hear nothing but good things about Deavers, however they are $$$ and if you are willing to do some trial and error, you can probably get 80% of the benefit at a fraction of the cost by building your own leaf packs. The only thing DIY spring packs won't get you is the double-wrap eyes.
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Old 03-23-2014, 07:30 PM   #4
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Re: Rear suspension options for lifted 2WD

Being that you have a Diesel Extended Body SMB, I doubt that your problem is being over sprung in the rear - that is a heavy configuration you have. Also the Camburg kit comes with ~4" lift blocks in the rear, not the 2.5" you are reporting to have.

Just this last week, we rebuilt and revalved some Bilstein 5165 Series shocks as they have nowhere near enough valving for a heavy van - especially rebound. I'll reserve my judgement on the overall design and quality of these shocks as related to our applications.

Check the height of your lift blocks and look at the profile of your springs at ride height. If the springs are inverted, you are under sprung, if not you may need the proper lift block to match the front lift.

This is a simplistic look at the issue, but a place to start. Once you get the spring and ride height figured out you will need a properly designed shock to really make it all work.

Airbags are not the proper solution - they are for conditional use, not for correcting improper spring rates. Most will actually restrict your wheel travel and all will result in a harsher ride than a proper spring will. They may feel better than what you have, but not better than what you should have.
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Old 03-23-2014, 08:15 PM   #5
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Re: Rear suspension options for lifted 2W

Relative to the rear spacers; Camburg is putting 2.5's I just measure them and confirmed. The van sits about two inches low. More spaces will solve that, but I would like the back to behave a bit more plush and controlled while on the dirt. I take a few hits and the back is jumping all over, the shock don't seem capable of damping the impact, and they are brand new. Im going to ask Deaver to look at the set up and comment, I will post the info I get.

Let me say that im a new owner and learning.... but I mountain bike and want to get to remote spots and enjoy the drive there without having to drive 5MPH.
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Old 03-23-2014, 10:09 PM   #6
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Re: Rear suspension options for lifted 2WD

Ok so I took a picture and figured out how to load it.
What can you tell me from the pic?

All comments very much appreciated.
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Old 03-24-2014, 12:50 AM   #7
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Re: Rear suspension options for lifted 2WD

You're sitting on the lower overloads. This is primarily why your ride is so harsh and unsettling.

In my opinion, you need to get off that overload leaf. Either add a couple more leafs, but keep the overloads in case you tow heavy in the future. Or ditch the overloads, and replace it with more leafs (probably 3-4, since you want to raise it too). Or, just weigh your van and order some Deavers.

Also, I see your new yellow shock. Looks like a Monroe gas-charged shock? You really need to think about some good MonoTubes, like what Ramsey puts into his ride improvement package.
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Old 03-24-2014, 05:22 AM   #8
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Re: Rear suspension options for lifted 2WD

If you haven't done it already, I'd start by weighing the van front and rear. If possible side to side too to get load on each corner; although not as critical. Everyone should have a good idea of how much each axle is carrying on their van/truck regardless of whether they are satisfied with ride or not.

Nick, since you stated you are new (I'll assume to vans and/or driving off road), I'll just comment that large vans are obviously not MTB bicycles, or even comparable to most car/SUV in my opinion. I think this mainly comes about because of two factors; too much unsprung weight and a chassis that is not very stiff in torsion.

I know you can improve ride somewhat but it's never going to be great under some conditions, so realistic expectations will save a lot of money in the long run. I'm not saying it can't be made better, but "plush" is very subjective.

By the way, an off-road bicycle has relatively little unsprung weight so it's easier to keep rear tire on ground. With heavy van axles and tires the shocks can help but if driving at a speed that matches the suspensions natural frequency, the ride will get bouncy and feel out of control. In my opinion it's essentially unavoidable. When that happens options include driving faster or slower until road surface undulations change pitch.


By the way, can you post a side view of your van? I'm curious to see how the lift looks on a 2WD extended body.
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Old 03-24-2014, 10:10 AM   #9
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Re: Rear suspension options for lifted 2WD

Quote:
Originally Posted by carringb
Also, I see your new yellow shock. Looks like a Monroe gas-charged shock?
For some reason, Camburg came into some old stock of Bilstein 5100's (the yellow ones with blue boots) that they are using up now. My van received the same ones.

Chance: I know you were asking the OP, but here's my EB

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Old 03-24-2014, 10:46 AM   #10
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Re: Rear suspension options for lifted 2WD

I have an EB27, that has much of the load on the back.

Carringb; I now see that I'm sitting on the lowers, Thanks!! The van has the towing package that the previous owner needed but I don't plan on using. I don't really have much load added, even the water tank is 1/4 full, maybe the leaf lost their "memory" its an 06.

You now have me thinking, replace the overload with a few leaf, that will give me the needed 1.5" lift and a more progressive damping. I can probably do that for a fraction of the full custom set. In the other hand putting customs and taking the blocks out will match the travel upfront. I'll have both options quoted and Deaver and report back late this week.

TheLetter3; you van looks sweet, love the tire rim combo.

Chance; How do I weight the truck? I live on SoCal, close to Irvine
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