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Old 09-11-2019, 12:37 AM   #401
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Originally Posted by Rulebreaker
Booster, thanks for this wealth of information! Very much appreciated!

Front:
I'd be interested in your opinion on the merits of the Moog 18004 vs the Husky SC20470. It seems the 18004 is constant rate while the SC20470 is progressive? Might this translate into smoother ride on the SC20470 at the expense of reduced vehicle height versus the 18004? The Husky seems to be listed as a constant rate where I looked and a cross for Moog 81006 which is shorter than the 81004 most have used in post 2002 models. You would have same rate but less length and lift. I don't like variable rate for constant heavy loads because the softer coils are over worked.

If I decide to seek additional height later using 3" spindles as some have done, would both of these springs likely still work for me? Some have done OK with them and some have not. Personally I don't like knuckle lifts because they mess up the suspension and steering geometry, and I can always feel it. I am pretty particular in regards to steering, others not so much.

Rear:
Is it just the adjust-ability of airbags that you prefer over using additional springs? For me, vehicle loading is pretty constant and we don't tow anything, so no trailer tongue weight to consider. (I'm just trying to rationalize the added cost and complexity vs. the benefits.) As for type of airbag; it seems some have used Firestone, while others chose Air Lift. Integral bump stops within seems to be a worthwhile feature. Is there a particular make and model of airbag that you recommend? Adjustability is nice, but most have found they ride a bit better also, but some claim worse. We are currently running ours the stock springs with the overload leafs removed. It really improved the ride, but there is only one other van doing the same and was just recently done, so not ready to say for sure good to go yet. With the overload out, we need to use bags with built in bump stops in case a bag pops as the bags sit where the original bumps were on the axle. Firestone bags would not need the internal because they are not mounted on the axle. I prefer the Airlift as they are larger diameter so less pressure plus they put the load directly on the axle tubes rather than on the lower spring bottom plate. Neither brand is bad IMO.

Shocks:
Bilstein B6-24-187435 front and B6-24-221948 for the rear seem to be the shocks of choice. Your thoughts? I gather if I decide to pursue 3" spindles for additional lift later, these B6 shocks might be too short? True? Knuckle lifts usually leave the lower control arm in the stock location and would use the same shocks, AFAIK. If you go more than about 3" up with springs, you will need longer shocks most likely.

Rear Sway Bar:
Vehicle has an under-hood generator (rather than under vehicle) so a Hellwig sway bar should work.

Overweight Vehicle, Wheels, Tires, etc.
Yep, vehicle is definitely overweight by about 3%, so I'll look at what I can do to lighten it. I do have aluminum wheels, so the offset issue you mentioned applies. Tires still have lots of tread, but when they're due for replacement I'll definitely look at upgrading wheels and tires to provide more load capacity.

As for front tire pressure; it seems 50psi is what's recommended on the vehicle nameplate as well as on Bridgestone load tables at the 2,050lb load per tire I have. I understand 210s tend to be lighter in the front than 190s due to the overhanging weight at the rear. Is the move to 65psi in the front, (presumably to improve handling and ride quality and to reduced heating and rolling resistance) likely to cause uneven/excessive tread wear in the center of tires over time due to crowning? It appears the plates are the stock ones or copies of the same pressures, and would be inteneded to cover an empty or full van without changing pressure. The 50psi squeeks in capacity at full load and would ride decently at low load, so a compromise on both ends. The 65psi is what most have found to be the best mix of steering response and tracking vs ride quality. Some like less, a few like a bit more. The tires will run cooler and wear the edges less at 65psi in most cases. Be aware you may have more weight on one side than the other by a couple of hundred pounds so splitting an axle weight can be a bit off.

Recently I measured ground clearance on my rig to the fresh water tank drain valve and it was a measly 4-3/8", so I'm definitely looking forward to gaining some additional clearance from these mods. Very believable at your weight. Probably low point right at the fragile tank valves and macerator, like we had.

Cheers,


Brian
I have the other van that is modified similar to Booster's: same airbags & overload springs removed, and both have large rear swaybars, albeit slightly different. Main difference is that I have aluminum spacers (replacing the overload leaf) on both sides, while Jim has only one side done. I may have to copy him on that too as I have a (small) constant pull to the right. So far we have about 750 miles on it and the handling and ride are great! (at least for a Chevy van, far better than stock methinks)

Regards, Dick
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Old 09-11-2019, 01:07 AM   #402
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Originally Posted by dicktill View Post
I have the other van that is modified similar to Booster's: same airbags & overload springs removed, and both have large rear swaybars, albeit slightly different. Main difference is that I have aluminum spacers (replacing the overload leaf) on both sides, while Jim has only one side done. I may have to copy him on that too as I have a (small) constant pull to the right. So far we have about 750 miles on it and the handling and ride are great! (at least for a Chevy van, far better than stock methinks)

Regards, Dick

I will expand a bit on the spacer to replace the overload leaf that is put into the stack like overload but just is a spacer. Dick used two to replicate the stock van spring height from the axle, which I also would have done, except I wanted to see if I could compensate for the fact that ours, and most other Chevies, required more bag air pressure on the driver side to sit level. To put more of the weight onto the leaf spring on the driver side only, I used the spacer on that side only. It did make it so our air bag pressures are even now when level.


I think all of this is because the driver side rear carries several hundred pounds more weight than the passenger side. The problem comes with the rear axle being rated at 6080# which is exactly the same as the tire rating of 3040# X 2. You get into a condition that if you are at max axle weight but have more on one side, that tire will be overloaded. It appears GM modified the spring or mounting to take some weight off the driver side, which transfers that weight to the passenger rear and driver front wheels. This resolves, for the most part, the possibility of overloading the driver side tire.


We are approaching 10K miles on our van with the overload removed and haven't had any downside issues to this point, but do have improved rear ride.
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Old 09-17-2019, 02:13 AM   #403
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Thanks all for your input.

Moog cannot confirm the suitability of their 81004 for my 2018 Chevy Express 3500 (their tables only go to 2006 model year) and suggested I contact Coil Springs Specialties (CSS) in St. Mary's, KS. Based on Chevy's part number for my stock front coils (20760345) they engineered a spring set to provide +2.50" trim height. These springs would have about 17.75" free length and spring rate of 1,645#/in (vs. 1,570#/in for the 81004). Price would be about $330/pair for their coils (incl. shipping) vs $257 for the 81004.

I'd be interested in peoples' thoughts on:

1) compatibility of the 81004 in my 2018 Express 3500
2) the merits of the proposed CSS coils vs the 81004
3) any experience with / reputation of CSS as a spring supplier (Anybody had experience with CSS? How did things work out for you? Would you use them again?)

Thanks, Brian.
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Old 09-17-2019, 03:18 AM   #404
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Originally Posted by Rulebreaker View Post
Thanks all for your input.

Moog cannot confirm the suitability of their 81004 for my 2018 Chevy Express 3500 (their tables only go to 2006 model year) and suggested I contact Coil Springs Specialties (CSS) in St. Mary's, KS. Based on Chevy's part number for my stock front coils (20760345) they engineered a spring set to provide +2.50" trim height. These springs would have about 17.75" free length and spring rate of 1,645#/in (vs. 1,570#/in for the 81004). Price would be about $330/pair for their coils (incl. shipping) vs $257 for the 81004.

I'd be interested in peoples' thoughts on:

1) compatibility of the 81004 in my 2018 Express 3500
2) the merits of the proposed CSS coils vs the 81004
3) any experience with / reputation of CSS as a spring supplier (Anybody had experience with CSS? How did things work out for you? Would you use them again?)

Thanks, Brian.

Hard to tell much from that information, I think. The 17.75" fee height is the same as the 81004 and factory springs so would go in without a compressor..


The problem comes in at what are they referring to at +2.5" trim height? Our 07 factory service manual gives a trim height at 4.3" in an unloaded van. Most have found that a spring like the 81004 give that same 4.3" trim height in a Chevy with near max of 4300# on the front. Stock springs are about 2" below that when fully loaded. Trim height per GM is measured under the van and is the distance from the pivot point on the frame of the lower control arm to the bottom of the lower balljoint.


Knowing what the spring wire diameter is and an the number of turns would give somewhat of an idea of how they compare. The springrate difference is not huge and they two springs could perform very similarly..


We have seen quite few 81004 springs put into Chevies later than 2006, and AFAIK, nothing has changed to this day to make it not work still.


No information that I have ever heard on CSS.
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