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Old 04-28-2016, 02:10 PM   #21
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This could get very informative! The whole harshness, rough ride, thing has been stuck in my head for several years as folks have tried lifts and spring changes, etc and the net results just don't add up for me. If you plotted the results on a chart, it would probably look like a shotgun blast instead of a pattern.

At least in the newer Chevies, I do think there are two spots that might significantly increase noise when you do the lift to stock height. In the front of a stock Roadtrek, the suspension is almost on the bump stops, as we have seen pictures of several of them. It is a beehive bump stop, which is like a Tibren, so it is really a very progressive rate spring rather than a pure stop. It is also probably urethane, which is a pretty highly damped material. When you hit a bump, a large portion of the impact is going to be taken up by the bump stop instead of the spring and shock, so it will likely be a bunch quieter than taking all the hit on the spring and shock like it does once lifted away from the bump stop.

In the rear of the Chevies they use a huge overload leaf on a moderate sized multileaf spring set. In stock form Roadtreks are compressed enough that the overload spring is in contact all the time, giving a very progressive, stiff rear ride. When we add airbags to the rear to get the height back to where it belongs, it lifts the van off of the overload leaf by an amount. Most of us have seen in the 1/8" range of clearance between the overload and rest of the spring stack. I think this smooths things out a bit because the airbags don't transmit sound as much as solid springs, are less progressive and they have picked up a portion of the load and impact. But on big bumps, I think you also get a "slap" when the overload leafs contact the rest of the spring. The only padding between them is a thin piece of very hard plastic, it appears. Of course, this also limits the amount of gain you get from the less progressive airbags, also. When we were doing the rear axle change last spring, I decided to do a little test to see if getting the overload further away from the rest of the spring would improve the range of improved travel in the rear. I took off the overload leafs (easy) and took them to a spring shop to be dearched a little. I arbitrarily picked 1/4" less arch. Once done, we could immediately notice a "smoother" ride. It did feel like we got more travel on bigger bumps and also got quieter. At the time, I had considered the quieter being possible, but if showed up noticeably. I do think it is a smoother ride, but I also now wonder how much of that is perception because it also got quieter. We currently carry about 30-40% of our rear weight on the airbags, so it is a significant amount.

I hope some more people do the earplug test if they feel their vans have gotten very rough riding. It would be interesting to see if this affects everyone, or just some people.
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Old 04-28-2016, 09:04 PM   #22
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Have you guys weighed your vans at all? I just had mine weighed, 6200! About 1200 more then a standard passenger van.
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Old 04-28-2016, 09:51 PM   #23
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Quote:
Originally Posted by etbike View Post
Have you guys weighed your vans at all? I just had mine weighed, 6200! About 1200 more then a standard passenger van.
Rear at 5250#

Front at 4230#

Not heavily loaded at the time. GVWR is 9600# on ours.
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Old 04-28-2016, 10:14 PM   #24
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A while back mine was:

Front: 4040 lbs
Rear: 4780 lbs

GVWR is 9500 for this van.

I haven't had it weighed with the new cargo box & there's maybe another 120lbs of batteries on board.
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Old 05-03-2016, 05:16 PM   #25
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Where can I find the 03 up coil spring replacement instructions you used?
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Old 05-03-2016, 05:58 PM   #26
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Ours came from Tufftruck, but they have quit supplying them because they got tired of complaints of harsh ride. This is where a lot of the variation in opinions has come from, as Tufftruck have been a large proportion of the spring changes done. I don't know of a spring being offered that is the same as the old Tufftruck. Their current offerings are different so I have no idea what results you would get.

You could have anything you wanted made by Bill Erb, in California, as he makes his own springs in house. I think the shop is Valley Suspension or close to that.
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Old 05-03-2016, 06:13 PM   #27
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I guess all I need to know is did you have to break a ball joint loose or does the spring come out when compressed?
Haven't changed a spring in 30 years.
Having my springs made by coil spring specialitys.
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Old 05-03-2016, 06:32 PM   #28
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A stock height spring, or shorter, can be changed by taking the lower ball joint loose and lowering the a-arm with a jack. I chose to hire it done as it is a bit of a frightening procedure to see the bowing, still compressed, spring in there. They didn't use a compressor on ours when they did them, but it was snug going in.
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Old 05-03-2016, 09:52 PM   #29
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I dropped the lower arm (supported by a jack) by removing the pivot bolts. Compressing the spring and handling it etc. was very physical but the hardest part of the job was getting those pivot bolts to line up.
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Old 08-03-2022, 03:06 PM   #30
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Have to say many thanks to those who have shared their knowledge and experience. Booster had referenced Markopolo and this thread for my 5.7L '02cRT190P after I mistakenly posted on a '03 forward suspension thread. Have had good fun and an education reading many RT suspension threads before finally coming to this gold mine of knowledge. My RT's rear leaf pack with 69k miles sits firmly on the overload spring. Agree with Booster's important lesson that in order for the springs to function the leaf spring pack has to have clearance to the overload leaf. Not having the skill set to determine the amount of sag in the existing springs, I will assume that both the front and rear have sagged equally and will benefit with new components. On my Chevy PU's that have carried the old '89 Lance, I opted for Hellwigs LP35's over airbags due to stories of Baja failures. Was always able to adjust the springs to keep the spring pack off the overload, something I did not realize important until reading Booster's comments. The Hellwig LP35 #9511 with the #25250 mount kit specified for the '02 G3500 I believe is not going to work in the RT. The end adjustable Ubolts and the cross bar are too wide for the 3/4 -1" clearance between between the front of leaf spring pack and the frame. Also, there is the RT gas filling pipe on the driver side that limits clearance. The best alternate, I'm thinking to the Hellwig is the Super Spring SSA-12 (2600#) There is a SSA-13 (3500#) but it's for the Chassie G3500. The guys at Super Springs recommended the SSA-12 over the SSA-13. The rear suspension plan seems to be set with the choice of new Bilsteins all around. I'm seeing for the rear the B6 #24 221948 for plus 7300 GVW. The fronts have 2 different part numbers to figure out. For the B6 +7300 GVW they specify 24 025652 or a 24 024808 no indication of weight rating. Markopolo has shared a lot of valuable information and experience for the front spring replacement. I had also accumulated an initial list of the front spring options however without the specs of each except the Moog 81012. I did not find the Moog 81008 it having an extra 1.13" free height over the 81012 and a load rating of 4172 lbs vs 2410 lbs for the 81012.
On his post number #2 in this thread Marko shares a list of Moog springs and their specs. The specs are all similar except the free height and the Load. With my front axle label saying 4300 lbs and cautionary info not to exceed labeled weight rating, maybe the choice should be the 81012 at 2410 lb and the fitment offered on RockAuto, specific to my rig. Maybe the 81008 could be the choice with the need to cut it 1/2" in free height. Would that then translate to an approximate load rate of 3291 lbs for the cutdown 81008? Does 1/2 the free height difference translate to half the load? Marko in post #7 says "if ordering again" he'd go with the 81012 and in post #8 says the 81008 works with his diesel and 5 batteries forward of center. With a 5.7 L and only my fat rear end maybe the 81012 is the best but I would love to get some front-end lift in addition to the remedy of the 69K miles sag. I'd have to be precise with the cut on both sides if the free height is related to Load and it's unknown how a cut would go. Thanks for the opportunity to post on this thread and thanks again for the knowledge shared.
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Old 08-03-2022, 09:54 PM   #31
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As far as I know, the "load" rating for the Moog coils being discussed here is how much weight it takes to compress the spring to 14". The bar diameter is the same and the only difference is the length or height of the coil spring. Taller spring means more weight to compress it to 14" compared to a shorter spring.

My guess is that the ride stiffness would be the same due to the bar diameter being the same. It's not a soft ride. Booster would know if my guess is right or wrong.

If we could find a tall spring like 16.5" with a 0.9375" diameter bar like the OEM coil then that might be ideal for max lift and ride comfort. All of the taller springs I found have a 1" or so bar diameter. That just my assumptions though as I don't know that much about the technical side of this stuff.

Moog 81004 to 81012.JPG

It's probably a good idea to figure out what you'll do for the rear springs. I added Airlift bags so it's kind of easy to get the van level front to back and side to side.
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Old 08-03-2022, 10:45 PM   #32
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As Marko said, not a lot of options on springs and a 1.032 diameter wire spring in the older style will be stiffer than in the newer style do to control arm pivot to wheel ratios, I think.


The idea of a taller spring with smaller wire is a great idea if you can find one. It does appear that the older and newer Chevy van generations use the same outer diameter of the spring itself at 6.070". I also know from our van and others that have been mentioned, the later version vans came stock with a .937 or 1" diameter wire spring that is 70.75" tall. The 2500 van may have been on that is shorter, though, also.


The longer spring could be shortened although you would lose the semi closed end so grinding a flatter end on it would probably be needed, or even better find a local spring shop that could close it up to be flatter on the last coil as long as they didn't heat it to bend it.


GM probably has such springs new, but they won't give anyone the specs on them to know without buying them to measure yourself. Perhaps a local suspension shop would know, but not likely. A trip to the junk yard might be in order to look at newer vans to measure the spring wire diameter and count the coils. The longer springs will have more coils so you can tell about how long they will be compared to each other when uncompressed.
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Old 08-03-2022, 11:40 PM   #33
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Thank you for this informative thread and all your comments. I am trying to understand the end result of the dynamics of these coil spring options without understanding how it all really works. The Moog 81012 came up in Rock Auto for my rig. I had seen multiple threads and posts including yours and Booster's mentioning Moog so with Rock Auto marketing the coil, with your adventure with the 81008, the idea of a Moog spring replacement is good one.
I equate ride stiffness with drivability and that is always changing with high aspect of the RT and road and weather conditions. Safe secure drivability overrides the soft or harsh element for me. I like to feel the road and the tires, wheels and suspension all come together for the ride. It looks like Super Springs SSA-12 in the rear for me. I'll revisit the idea of the SSA-13 if it fits and is appropriate for the weight requirements. They are semi adjustable vs the fully adjustable airbag but with a steady load of the RT I think it is possible to find a sweet spot and get the leaf pack off the overload. Thanks Again
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Old 08-04-2022, 12:19 AM   #34
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There are a few oddities with handling and spring rates and sway bar rates are among them because they work inversely to the end they are on and to at least my logic.


If you have a vehicle that understeers, or "pushes" in race car speak, it means the front has less traction than the rear. It will plow off a skidpad by sliding the front wheels. If it oversteers or is "loose" in race car speak it will lose the rear end first and spin off the pad. With all the rear weight in the vans, it would be near impossible to make them oversteer unless on ice. The vans do understeer horribly, though, and that trait makes them less responsive to steering inputs which gives them big corrections of the steering wheel needs and can be a cause of wander.


Both springs and swaybars help the traction on the end they are NOT on. If you understeer now, to make it better you would add more spring rate in the rear or add a rear swaybar. That means also means that if you add stiffer springs to the front, the rear will gain traction and the van will understeer worse, degrading the handling, not improving it. The higher rate will help rocking and lean some, but that happens on both ends.


IMO, getting the front to be firm enough to not porpoise on dips is the best place to be, not a lot stiffer. Add a big rear swaybar and the van will handle well and can be at a higher height without handling worse due to the height. Putting stiffer rear springs in will help the understeer issue unless you also increase the front springrate and have it negate the rear benefit.


Too stiff of springs on either, or both, ends will make the van pitch on single wheel bumps and dips which can throw you around and make control harder. A big rear swaybar can get rid of a lot that pitching, though, if you have one. It will still rock some, but be more easily correctable.
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Old 08-04-2022, 03:24 AM   #35
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Thanks for the information. I get the concept of finding a balance between the front and the rears. Went looking for the OEM for the Van. My build code is 6XD , the part number is 15058106 and is discontinued. The part is described as 1 Ton medium duty and 3/4 ton medium duty. I will measure my front coils tomorrow and rethink everything
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Old 08-04-2022, 10:38 PM   #36
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Made an effort to measure the existing coils which I assume are OEM. One look and you can feel the pain the rust and the sag. They are sitting about 14 high, hard to measure exactly and the wire size is 24mm about .94". Finally made some ramp blocks from scrap wood about 2 1/2" high. Like that look of clearance in the front. Made a plan, ordered Bilsteins and the rear helper spring SSA-12 Super Spring. I'll do the shock and the SSA-12 install. Hope to get the rear leaf bundle off the overload. I'll give a drive with the plan to have Bishop Automotive do a front end evaluation. They'll let me order all/any front end components including coils if needed. I'm partial to Moog for the front end and still thinking of Moog for the coil most likely the 81012. While ordering the SSA-12 and discussing their 3700lb coil SSC-12, he gave some "mechanic notes" specs that seemed different. 15.3 for the free height. 12.75 installed height, 4.02 inside diameter. 0.937 Bar diameter. 1450 spring rate and 3700 lb rating. Was invited to call the Coil Pro, Mark tomorrow. Who could ask for more?
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Old 08-10-2022, 02:40 PM   #37
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Progress report: Got the rear Bilstein's installed on the 02 Chevy RT. The fronts looked easy enough. Despite several BP blaster applications on every nut and bolt I could find in the front end done the day before, I managed to break off one of the 5/16 x 18 lower shock bolt. Now if there was j nut as on the rears, not a problem. After close inspection I noticed the grease blobs on the ball joints of both the upper and lower control arms form my maintenance the week before. Made the decision to replace everything including the coils with Moog parts from Rock Auto and the front steering linkages also Moog Parts. Delivery is by the end of the week. I should be able to handle the suspension replacements but will leave the steering to the Shop. Received the pricey supper springs SSA-12 on Monday. Had them in by early afternoon. I started with the passenger side and encountered difficulty with RT additions. Tech support at Super Springs was very helpful and was able to deviate from the install instructions a bit to get them installed. The driver side was much easier with only the gas filler tube in the way. I settle for the bottom hole on to each shackle end, the least of spring effect and got a clear 1/2-inch rise of the leaf pack from the overload spring. Did a short test run and have to say I was pleased with the handling over small bumps and around curves in the road. Boosters' idea to get the leaf pack off the overload is golden. Can't wait to get the new Moog 81012 coils installed.
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