Met with Jeremy Johnson today - not being an Suspension adept/Engineer I was unable to share with him by phone my exact needs & the measurements at play presently.
After driving down with the Van & meeting him in person, less than a foot away, I was even less able to communicate exactly what I needed nor understand him.
So I gave him the keys & we went for a drive - instantly he knew & even though I didn't, I knew I was in the right place.
Friday we are going to begin with the 2inch spacers, 4 new Bilsteins, new control arms, keep the Erb* Coils or when they are out, throw in some new but stock Gas coils he upgraded from a 3500 Chevy or try new but stock Diesel springs.
He said the Erb Coils are big & thick but not necessarily fatiqued but he would know better once they are out & caliper tested.
The shocks are dead.
WHAT IS THE OPINION OF MY LEARNED MEMBERS?
Try the stock Gas with the spacers or the Diesel units with spacers?
(If you had the options of replacing the Erb Coils, he did say it looks like they are giving me the height I wanted originally.
The Bilsteins are the Heavy Duty B6 yellow blue units - he said longer shocks just won't fit in there (or maybe I heard him wrong)
Easy stuff first.
The Bilsteins are great shocks. The only downside is if you get too high in the lift, they can get to be too short, and we haven't found a longer Bilstein that has the right lower mount. They will only work well and survive if they use GM style upper shock mounts though, so it the Biilsteins don't come with that style they need to get them.
I assume they would be putting in stock control arms, or control arms that have the same geometry as stock? If so, it is a good way to get all new balljoints and pivot bushing without all the work and potential for damage of manually replacing them all. Doing full arm replacements is getting to be the norm these days.
I will jump to the end of your comments first, here. How high you currently are is pretty easy to measure, as we have those dimensions. GM gives a "trim height" that actually measures the suspension height, so they could check that while on a drive on or alignment rack. Nearly as accurate is checking from the ground vertically up to the wheelwell lip, at the center of the wheel. A stock Roadtrek 190 will usually be about 33.5" to maybe 34" depending on the weight in the van. If he is correct that the Erb springs are still at the height you want, the measurement will be at about 36". All of this is with stock tire size. I think you had mentioned that your was up 2.7" originally, so you would likely have been at 36.7" coming out of Erb's shop. If you truly are at the height you wanted originally, there would be no need for new springs or spacers, just the control arms and shocks, plus any other worn front end parts.
Now a word of warning that they probably already know, but here goes. If the Erb springs have not settled about .4", they will be longer than the stock springs, which just barely can be installed with compressing them. What this means is if they mistakenly think that they are stock length and just try to take them out without compressing them first, someone could get hurt by a flying spring.
If you use the 2" spacers in the springs, I think you would want to stay with the stock spring design, although it may put some extras stress on the part of the spring where the spacer isn't. The stock springs are overloaded by a Roadtrek, and that is why they sit so low, so if you just stiffen part of the spring, the other part does more of the work when it is already overloaded.
The one complaint I would have is that Supersprings does not publish what wire size their spring are, or how many coils they are, which would give us a better insight into how they will feel and how high they will lift. Marko had found some info that said the diesel spring they sell SSC-14 uses 8 turns of 1.06" wire, which would make it the same as the original Tufftruck springs that you did not like when you did them a few years ago. The stock springs are normally at about 7 coils of .94" diameter wire, and will be as mentioned earlier. The Erb springs are about 7 coils of 1" wire, but are longer than stock or diesel springs so get more lift.
Supersprings should be able to tell you how their springs fit into the above categories. Most of us are using springs that have 8 coils of 1.03" wire, which seems to give the best combination of good control without being too harsh, and also matches the damping rate of the Bilstein shocks well. In the stock 17.7" free length, they will give you about 1.75" lift which will be about 35.5" to 36" at the wheelwell as measured per the above method. This wheelwell height will put the van nearly right at what GM says the van should be for trim height, measured at the suspension, and will make for getting a good alignment. With a 1.03" wire spring as mentioned, you would not need the spacers in the springs. Several companies make these springs so they are off the shelf available if you decide to go that way. The springs are also linear, not progressive, which to me is better with the nearly constant front weight we see in the Roadtreks. The spacers will make the setup quite progressive.
What I know you will find, with the new control arms and shocks with good upper mounts, is that the van is going to get a lot quieter, which from what we have seen will also make it appear to be riding smoother. The extra noise has the affect of making the ride seem rougher for most people.
Obviously, you will need a good alignment when done. The Chevies seem to like 1/16" toe in (more will give tire wear), zero to +1/4 degree camber with it the same on both sides, and then the max caster you can get while keeping .4 degrees more on the right side. They drive very well when set there, but the specs allow a lot variation that can make them worse, so the closer to those numbers they can get, the better it will drive, I think.
