OEM E-350 spring rate?

[86Scotty]

I've almost fully built my 2011 E350 and also RIP'd the Quigley conversion with taller front springs and Fox shocks all around. As expected, I now have some sag in the rear.

I realize there are several ways to fix this. Airbags, add-a-leaf, perhaps taller blocks which I would never do and also the usual players in aftermarket springs such as Deaver.

BUT, I'd like to focus on OEM spring offerings first and I need to know what I have under it now. It isn't as easy to figure out as I first thought. The Ford dealer and my VIN point to my van having 8C2Z5560RB springs but I do not know what the actual weight rating of these is. Anyone know?

There are several aftermarket lift and/or heavier leaf packs I could go with per RockAuto and other online sites but before I make a decision on that I need to know where I'm starting from.

RockAuto, a great resource for comparing parts for any vehicle, offers E350 springs in 2350, 2775, 3460, 3600, 3750, 4000 and even 5000 lb. load ratings. My van was around #6800 when I got it and is now just under #9000 fully converted. I suspect my final fully built weight after I add a pop top will be in the 9500 range.

[Mikerson]

I have been thinking about this problem too. One suggestion I have is to count the leaves in your pack, then take look at SDtrucksprings.com to match up the “capacity.” These are OEM replacement springs. Since the width is fixed, and I assume the leaf thickness is standard, then you should be able to determine your pack by only the leaf count. I’m not sure how the capacity is typically defined for the rear spring packs. Perhaps the load that makes them go flat. I contacted sdtrucksprings to inquire about the spring rates for the different capacities, but they weren’t able to tell me (furthering my suspicion that these are just like OEM). A while ago I found an SAE publication to calculate the spring rate based on number of leaves and geometry, but haven’t dug into it yet.

https://www.sdtrucksprings.com/index...ear%5B%5D=Rear

[1der]

If you are happy with your current ride characteristics why not add a block and maybe do the Agile style add a leaf? How much sag are you seeing?

New springs will certainly introduce a different ride.

[86Scotty]

I already have 3" Quigley standard blocks and don't want a taller block than that. I would prefer to have less.

[Normal_Dave]

I'd call Bob (or Junior) at ATS Spring. Give them your current leaf count/arrangement and your target weight capacity. I got great service and pricing from them and they took time to work through the specs.
https://www.autoandtrucksprings.com/

I'm sure you've already done this but, check the door tag and get the 1 or 2 digit spring code, lower right, then use the lookup on SDTruckspring to get the corresponding stock replacement spring, then you can upgrade from there. (ATS will have the same spring offerings).
https://www.sdtrucksprings.com/ford-...-code-listings

I took a look, found Spring code "R" on Ford website.


That converts to this:
43-1041 2,775LB 4/1 leaf, 4" arch.
https://www.autoandtrucksprings.com/...43-1041/#tab-2

The HD version of this spring shows:
43-1041HD 3,750LB 6/1 leaf, 3-1/2" arch.
https://www.autoandtrucksprings.com/...-1041hd/#tab-2

May not be relevant to you but I gained 3" over my stock worn out springs on my E-150 Chateau going from them to the "HD" version of my stock springs. 1,685LB to 2,250LB. I recognize part of this was due to worn out springs, so likely 1.5-2" over fresh stock spring. 2/1 stock to 4/1 HD.

[86Scotty]

Excellent info, thanks!

[boywonder]

To determine spring length/height at a given load, you need the spring rate (lbs/in) and the free length. From there the math is simple....


F=K*X


F is force/load


K is the spring rate (usually in lbs/in)


X is the displacement (in inches)



When the spring is unloaded (at free length) F=0 and X=0. Compress the spring with some displacement X and calculate the Force F. Subtract X from the free length.......now you have got the load for a given length/height.

[arctictraveller]

I was in a similar situation with blocks in the rear causing axle wrap and there was sagging in the rear. I decided I wanted a more progressive spring that rode better (softer) but supported the weight. My solution was to have new springs made based on the current weight of each wheel, and arched enough to eliminate the four inch blocks. I went with an eight leaf pack, (more but thinner individual leafs) The ride was improved (more supple) and the axle wrap was reduced by 90%. Unfortunately though, the rear was a bit lower than the front but I lived with it for a year or so but then I hung a motorcycle off the back that was cantilevered out about three feet and the sag got worse. So a couple months ago, I had the rear springs re-arched a bit, and then added one more leaf. Now it sits level and doesn’t sag even with the bike loaded up. Depending on what you hope to accomplish, you can also get your springs re-arched to increase the ride height, (perhaps enough to eliminate the blocks) add another leaf, or just have a new set made. Adding another leaf is probably the cheapest option, but you might need longer U bolts. My multi leaf pack rides noticeably better than the old springs.

[boywonder]

How much $$ to get them re-arched?


..and did you bring them the springs? Or the shop removed them?

[86Scotty]

Originally Posted by boywonder

To determine spring length/height at a given load, you need the spring rate (lbs/in) and the free length. From there the math is simple....


F=K*X


F is force/load


K is the spring rate (usually in lbs/in)


X is the displacement (in inches)



When the spring is unloaded (at free length) F=0 and X=0. Compress the spring with some displacement X and calculate the Force F. Subtract X from the free length.......now you have got the load for a given length/height.

Professor, I just want my van to look cool. Is that too much to ask?