Some advice on a Chevy Suspension Upgrade

[booster]

Originally Posted by rivers2run

One thing Bill Erb did was raise the front first then he took measurements and decided if the rear needed work. He didn't want to make any determinations until he had seen what lifting the front did. As it turned out it did especially the drivers side. You might be a bit skeptical if someone makes full assessment right off the bat.

The rears are much easier to tweak for final level than the fronts, so that is not a bad way to do it, as long as you know the front, especially in the Chevies, will likely be uneven do to rear one sided sag. That would probably be why one side of your front showed more difference than the other. Sag in the left rear can remove weight from it and the right front and add that weight to right rear and left front.


Once the front is in and settled a bit, he could look at what it would take to get the whole thing level and probably used a bit more spring in the left rear to get there.


This is where it gets much easier with airbags because all you need to do is change the pressures in each side to get level.

[mangomike]

okay ,,, I think I get what I did wrong. So, what I should've done was see if the knife blade would fit in between the "bumper cushion"and the overleaf. I think that looking at the picture and from what I remember,,,as you said,,, there isn't any room.so, that leads me to think that the people that I spoke with and got the quote from ,,,,did not give me very good advice with saying that the shocks should fix everything?
So, now it seems like I'm back at square one . I sure wish I could find a good or really good suspension shop.
So, again let me display my ignorance. This is what I think the parts of the suspension system that we are talking about do. in the simplest terms
Springs ,,, front and back
if I understand correctly (which I probably don't)the Springs basically hold the vans chassis up and give it some suspension , handling qualities, etc.
the shocks
basically smooth out what springs are doing.???
So ,if the above is correct unless the Springs are doing their job putting new shocks on would be pretty relevant. I'm saying this because if the Springs in the rear are sitting on the overleaf and the springs in the front are allowing the front to sit on the bumper stops ,, putting new shocks on ( which is what the shop that I went to suggested and I did emphasize to them to look at the springs) will not help much.
so it sounds like I should be thinking about some type of rear springs
And new front Springs ( coil Moog?) for the front. and, then move on to the shocks, and maybe the sway bar. I'm just trying to figure out a sensible order of the progression ?????????
and then I have to find a reasonably good suspension shop
there is a shop called Tampa Springs Truck repair , they are not very close to us but they have been in business since 1927 (or something like that) I'm going to give them a call on Monday and see if they are willing to take a look ( diagnose) my van. I haven't wanted to go to them because of the distance but, I guess if they're the right shop I won't worry about how far away they are .
anywhere the above is what I'm thinking today.
As always thanks for the help and advice Michael

[booster]

Yes, springs hold the van up and determine how much it will move with increased or decreased load up or down. The shock damp out the oscillations the springs would have by themselves, like bouncing for long periods, and also slow down any fast motions of the wheels to prevent very quick geometry changes.


In general, the springs and shocks need to "match" within a moderate range. Stiffer springs need higher damping shocks or the springs will overpower the shocks and the vehicle will bounce. If the shocks are too stiff for the springs, they will greatly increase harshness and limit spring travel over bumps too much.


In the case in question, it appears that a lift is desired, so that will be springs in front for sure, and air bags (my preference) or springs in the rear. I would do the shocks at the same time as the OEM versions don't last very long and would likely be overpowered by the new springs. It will likely be less labor cost to do at the same time as the lift as some of the labor is redundant.

[Asphalt Addict]

Hi all, seems like I already know you as I've been reading about suspension on this forum for some time. Just joined and I first want to thank you for all your expertise.

PW Lexor, similar to RT 190 on a 2008 Chevy 3500 Express. Bilstein shocks. 108K

I have wanted to raise this van since I bought it 5 years ago as I go off road often, many scrapes to prove it. From the recommendations on this site I just had Moog 81004 coils in front and Air Lift bags in rear installed.

Raised about 2-2.5 inches in front.
Front: L 35.75” R 36” (measured from ground to top of wheel well
Rear: 37.5” with 70 lbs

One mistake I made was to have new Michelin tires mounted just before I dropped the van off for the suspension work giving one more thing to consider.

It appears the van floats a little going down the highway. Tire pressure is what I’ve always used 60 front 80 rear. The tires are the latest version of the same tires I’ve always used. But it could be the tires that are making it float.

I put 70 lbs of air in the bags, (up from about 55, first run) seems a little better but not like before suspension mods.

Front end was aligned at time of suspension mods.
Does the front end alignment need to have a special adjustment?
Will air pressure in bags affect the ‘float’?
I probably need to put a few miles on before final adjustments but I’m also thinking of lowering front tire pressure to 50-55.

Anyone have the floating experience? Thanks for any thoughts on this. Jim

[booster]

Originally Posted by Asphalt Addict

Hi all, seems like I already know you as I've been reading about suspension on this forum for some time. Just joined and I first want to thank you for all your expertise.

PW Lexor, similar to RT 190 on a 2008 Chevy 3500 Express. Bilstein shocks. 108K

I have wanted to raise this van since I bought it 5 years ago as I go off road often, many scrapes to prove it. From the recommendations on this site I just had Moog 81004 coils in front and Air Lift bags in rear installed.

Raised about 2-2.5 inches in front.
Front: L 35.75” R 36” (measured from ground to top of wheel well
Rear: 37.5” with 70 lbs

One mistake I made was to have new Michelin tires mounted just before I dropped the van off for the suspension work giving one more thing to consider.

It appears the van floats a little going down the highway. Tire pressure is what I’ve always used 60 front 80 rear. The tires are the latest version of the same tires I’ve always used. But it could be the tires that are making it float.

I put 70 lbs of air in the bags, (up from about 55, first run) seems a little better but not like before suspension mods.

Front end was aligned at time of suspension mods.
Does the front end alignment need to have a special adjustment?
Will air pressure in bags affect the ‘float’?
I probably need to put a few miles on before final adjustments but I’m also thinking of lowering front tire pressure to 50-55.

Anyone have the floating experience? Thanks for any thoughts on this. Jim

Great questions, I think. Your heights are just about what would be expected, so that looks fine.


The Michelin tires will feel a bit "softer" as in smoother but I don't think I would call it "float" which would normally be what might be called porpoising. Most have found that 65/80 tire pressures work the best for handling with Michelins, I think, about the same as other tires.


The van will ride different up higher as you have gotten your suspension travel back which was limiting because you would hit the bump stops and rear overloads all the time. You will certainly feel more travel both front and rear, and the higher you go in the rear the less likely you are to hit the overload so it may be more noticeable. We normally run our Airlift rear bags at 40-50* but we also don't have the overload to hit so lower is fine. The rear of ours does feel fairly soft, but controlled, I think, but some might think it is more bouncy. It certainly has more travel than it used to, but you need that to get rid of the harshness. 50 psi in the Airlifts pick up about 1/2 of the rear load in a Chevy.


How many bounces to you get if you go over a moderate sized dip at highway speeds. One to one and a half would be pretty typical I think, and this will give a better idea if the shocks are doing the job.



How old are the Bilstein's, perhaps thay are getting a bit soft and getting overpowered by the newer springs and bags?


As with almost every vehicle, the alignment can be "in the green" and not very good and not the best. What I like, and some others have done and were happy with are:


Camber +1/8* both sides-if any variation only more plus never close to zero or negative-and not more than up to 1/4*


Caster at as much as you can get while still getting the above camber--with .5* more plus on the right than the left, which is quite important--


Toe should be in 1/8" if the front end parts are tight, and more if things are getting loose


Pretty basic and close to the centerpoints on the ranges given in the service manual.


I think the Lexors came with the factory steel wheels on them? If so good, if you have aftermarket wheels on it they likely would be the wrong offset and can feel different.


My guess would be that the tires and airbags are both feeling a bit softer than what you are used to, and you are also noticing the extra travel you now have (a good think IMO). About the only thing I can think of that would create a bad float or porpoise would be if the shocks are not good, but Bilsteins usually hold up well. Do be certain the shock mounts all are good and got tightened properly.


Also take a look to make sure they got the swaybar hooked back up and tight.


Let us know what you find out as that is always good to get into the pile of different results folks have seen.

[Asphalt Addict]

Thanks Booster.
Steel wheels. Good.
Bilstein’s should be good as I asked them to check. Maybe they didn’t check the rear but they had to remove the front. I have about 90k on them. Had them in other vans with more milage. Only had one go bad.

Haven’t driven it much yet. We live in mountains without highways. Going to bay area this week for TG. I'll have more experience when I return. I’ll pay attention to the bounce.

I think you may be right that I’m just not used to new tires and airlifts, and being off the front bumpers. But I am loving the extra clearance. It may be only a couple of inches but it looks a lot higher. I can actually get under the van without jacking it up.

I’ll give it some miles, play with air pressure in bags and tires. 60/80 now, I’ll try 65/80 and 55/80 later. I’ll also check into the shocks. I’ll give it some time and have the alignment checked, too. I’ll post my results.

Thanks again for your input.

More questions; do the AirLift’s lose air? How much is normal?
The install manual says it is common to lose 2-4 when first installed then says to check weekly.
I got the Ultimate but did not get the on board compressor. I also noticed just checking the pressure drops it a half pound or more.

Cheers, Jim

[markopolo]

You could describe what you mean by float.

Re: the alignment - on my older van, after I installed the new coils and air bags, the alignment place said there were camber/caster knock-outs that had to be punched out to allow the adjustments needed. I don't know if the newer vans have that.

[booster]

Originally Posted by Asphalt Addict

More questions; do the AirLift’s lose air? How much is normal?
The install manual says it is common to lose 2-4 when first installed then says to check weekly.
I got the Ultimate but did not get the on board compressor. I also noticed just checking the pressure drops it a half pound or more.

Cheers, Jim

On the losing air from the bags, I think it is a bit of a variable thing. Some folks do top off regularly, and some don't have to. Our van sits inside in a most of the time heated shop, and it will hold pressure all winter without any change except from temperature. We have a compressor and mechanical fill control panel with double gauge so I don't lose any from checking.


I think giving it some time for you to adjust to the new reality is a good idea. You have likely gotten very used to the pitching back off the front bump stops and rear overload leaf, so having it not do that is a really different feel to the ride and drive.



Good luck on your testing

[rowiebowie]

Originally Posted by Asphalt Addict

Bilstein’s should be good as I asked them to check. Maybe they didn’t check the rear but they had to remove the front. I have about 90k on them. Had them in other vans with more milage. Only had one go bad.

Cheers, Jim

You've gotten your money's worth on your Bilstein's. Shocks wear out gradually and if you are the daily driver, it's hard to notice how much they have softened. My be that a new set will get you back where you want to be and control the "float".

.

[Asphalt Addict]

You may be right. I'll have to check them. I had them on my 94 dodge PW for over 150k and they seemed to work fine. I sold to my neighbor. I'll have to ask if he had them replaced. I've heard mixed reports on how long they last, or supposed to last.
Most of my milage is highway but short trips on rough off road probably makes up for it.
Cheers

[mangomike]

Hi
Is there a mechanical way to test shocks
Thanks
m

[booster]

Originally Posted by mangomike

Hi
Is there a mechanical way to test shocks
Thanks
m

The manufacturers have testers that measure gas pressure and damping, but all we have is by hand.


The Chevy rear Bilsteins are very hard to compress by hand when new so they much have quite high gas pressure. If you take off one end while under the van, they should be a two hand push, or close to, for most of us geezers. Once compressed they should come back relatively slowly. The fronts are lower gas pressure, so will compress more easily but still should be slow coming back.


One big thing is to feel for any jumping when they change direction, as that is a sure sign they are developing issues.

[peteco]

Originally Posted by booster

The manufacturers have testers that measure gas pressure and damping, but all we have is by hand.


The Chevy rear Bilsteins are very hard to compress by hand when new so they much have quite high gas pressure. If you take off one end while under the van, they should be a two hand push, or close to, for most of us geezers. Once compressed they should come back relatively slowly. The fronts are lower gas pressure, so will compress more easily but still should be slow coming back.


One big thing is to feel for any jumping when they change direction, as that is a sure sign they are developing issues.

Wouldn't it be possible that the shock could pass this hand pressure test but still have failing damping function?

[markopolo]

There's a basic on-vehicle test:

1. Use your hands in order to lift up and push down each corner of the vehicle 3 times.
2. Remove your hands from the vehicle.
3. Locate a shock or strut that exceeds 2 cycles.

[booster]

Originally Posted by peteco

Wouldn't it be possible that the shock could pass this hand pressure test but still have failing damping function?

Possible for sure, and the how much experience someone has in doing the test would likely make a huge difference. Gas shocks make a determination harder, I think.


Back in the day of 50-50 damping only shocks, it was pretty easy to get a good idea if you had at least a rough idea of how much effort it should take to push though the damping at what ever speed you are pushing. You feel the resistance, it is the same in both directions, and it is smooth with no "gap" in damping at direction changes.


With gas shocks, one thing is easy. If they don't extend on their own, they are bad.


The damping test is much more complicated with gas shocks because the gas pressure is against you when you compress them so it is harder to determine what is gas force and what is damping, especially in high pressure ones like the Bilstein rears in a Chevy. If you have compressed a new one of that particular shock to know, it can get tough to tell what is going on. The extension damping test will happen by itself as the shock self extends, and any change in gas pressure will affect that also. It is essentially impossible, I think, to compare the compression and extension damping for how even in a gas shock unless you have a good one to compare to.


At least in the van you have two of each shock, so you can compare those two to each other, and if they don't match they are bad as a pair so you are done. If they are uniformly worn you won't learn much that way.


Marko's bounce test is good, but on a big, heavy spring, van it may take a couple of people to get a decent bounce.


If you are a person who likes to have numbers for things, (guilty here) you can usually get a pretty good reading for the compression side of it by using your weight on the shock with it on a bathroom scale and watching the highest number. I we all remembered to do that with new ones when we put them in, we would be in a much better place (I never remember to do it). If it is a gas shock, you can time how long it takes to self extend for that side of it.

[alaskasail]

I'm curious: what is the advantage of Moog springs over stock or other brands. I'm assuming they are more robust.

[User1213]

Originally Posted by alaskasail

I'm curious: what is the advantage of Moog springs over stock or other brands. I'm assuming they are more robust.

The Moog springs are being used to add some lift to the front end.

[booster]

Originally Posted by alaskasail

I'm curious: what is the advantage of Moog springs over stock or other brands. I'm assuming they are more robust.

As Hondo said, to add lift primarily, for most users, but also because they are a bit higher spring rate so they better control the very near maximum front weight of a class B.


The springs themselves are the same free length as stock, but have more coils (softens a bit and makes them less progressive), and are made with 1.030" diameter wire. Stock springs are in the .94" or a bit larger on some we have heard of.


The Moog should be a bit more durable without sagging because of the more coils, but material also plays a big role, so hard to predict for certain.

[mangomike]

hi
I promised updates so here's the latest
we went to Tampa spring company yesterday. I asked them to take a good look at the suspension and steering mechanisms.
Here is what they suggested
start out by changing the back Springs only ,,,, reasoning was that once the back Springs are in it will change how the front sits. This suggestion is to replace the existing Springs with and nine leave,,,, no overload spring
they also found that the alignment was pretty far out of whack ,,, they felt the worst was that it was very badly toe-ed out. they corrected that and suggested on waiting with the rest of the adjustments, until the back Springs go it.
We set up an appointment for 11 December two put the Springs
so I guess the approach would be a step at a time. They said that they didn't like to do too much custom corrections to the front springs ,,, due to its changing the geometry of the alignment. I noticed that in some of the posts you all of mentioned this as well.
what do you all think
again thank you all very much ,,,for your input
Michael

[booster]

Originally Posted by mangomike

hi
I promised updates so here's the latest
we went to Tampa spring company yesterday. I asked them to take a good look at the suspension and steering mechanisms.
Here is what they suggested
start out by changing the back Springs only ,,,, reasoning was that once the back Springs are in it will change how the front sits. This suggestion is to replace the existing Springs with and nine leave,,,, no overload spring
they also found that the alignment was pretty far out of whack ,,, they felt the worst was that it was very badly toe-ed out. they corrected that and suggested on waiting with the rest of the adjustments, until the back Springs go it.
We set up an appointment for 11 December two put the Springs
so I guess the approach would be a step at a time. They said that they didn't like to do too much custom corrections to the front springs ,,, due to its changing the geometry of the alignment. I noticed that in some of the posts you all of mentioned this as well.
what do you all think
again thank you all very much ,,,for your input
Michael

I may seem blunt on this, so take it for what it is


Rear springs without overload can take care of the rear better than the ones with overload, but it won't be as smooth as the airbags would make it, and you can't adjust height in the future. IMO, personal choice and not a huge deal.


Raising the rear without the front will increase the front caster a bit and will transfer a bit of weight (tiny) from rear to front, but will not make a huge difference, but what there is will be toward better.


Toe out is horrible for directional stability, they are right on that. You will notice a big difference with the toe set correctly.


The comments about not wanting to put in front springs to bring it up higher are plainly and completely wrong. If they bothered to check the "trim height" spec for a Chevy van, they would find you are way low now. All of us that have raisied the van about 1.75" to 2" to about 35.75" at the the wheelwell have actually put the front front suspension right in the middle of the Chevy trim height spec. RAISING THE FRONT WITH THE MOOG SPRINGS WILL GREATLY IMPROVE THE STEERING GEOMETRY, NOT MAKE IT WORSE. If they had just looked at where you are sitting currently compared to the front bump stops, where you will be nearly on them, they would know that, so one has to question their knowledge on that.


All this said, it is not uncommon for the shops to not have a clue of what is truly going on with any given model, especially one running near max weight like a Chevy class B (what they say for the front would be pretty good for an empty van), so they get some slack for that, but if you tell them to check the front trim height and they don't change their mind, I would find another shop.


Synopsis would be if you are more concerned with just a bit of lift and a bit of less harsh in the rear, rear springs will do it. Air bags would mostly be smoother and adjustable, so as mentioned both will work for lift and control.


The front without new springs will cost you a couple of inches of clearance compared to a spring change, and will leave you in the less than great range of steering geometry, and you will still get the harsh pitch up off the bump stop.


Good luck, I think you should be able to get it all straightened out.