Moog CC880S coils

[Redemption Road]

One more thought, being variable rate it would make sense the installed height to free height would be on a sliding scale, more compression at first, then less and more stiffness in compression toward the rated load.

Top of my CC880S coils are not touching, more like 1/4" between them, thinking my cush ride on highway is from those coils and when they do finally make contact I get the stiffness in ride.

 

[Bikersmurf]

That's with the factory 2wd radius arms right? I wonder how different the leverage ratio is vs a 4x4 radius arm setup. As my van sits, without a bumper or winch, I'm at 4440 on the front axle.

Correct. Factory 2WD radius arms.

Overall I don’t believe that the leverage ratio would make a big difference… but trying to think the length of the “lever arm” on a solid axle makes my head hurt. It’s been longer than I care to admit since university physics.

I would agree that you should subtract the unsprung axle weight. I’d ignore the “extra” tire weight, unless you’re going to add back on the weight of factory radius arms and stock tires. Offhand, I’d estimate the weight of radius arms and factory hubs and wheels will be in the same ballpark as larger and heavier off-road wheels.

As others have mentioned, the top coils are very close… in my case 3/16” apart… where others have said 1/4” apart.

In general, I’d follow MG metal works recommendations for springs as he has studied the physics far more carefully than we ever will.

 

[McGuyver]

The only difference the length of the radius arm is going to make, is in how far the axles move forward and aft for a given vertical displacement. It will have no effect at all on the spring rate or spring force.

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[RVflyfish]

I never did university physics, but I’ll always trust a guy named McGuyver.

 

[Bikersmurf]

I never did university physics, but I’ll always trust a guy named McGuyver.

My middle name is Macgyver… I don’t know this McGuyver guy, but I suspect he’s an imposter

 

[Raul]

Any other items to consider? Raul, did you determine the CC860S using calculations or trial and error? I know you've played with springs a little and I would lean toward experience vs what the math may determine, ideally middle ground from both or real close.

I did some calculations, but I've never weighted my van yet. I tried all three. I went with the 880s first since this was the general consensus. Too stiff, good height. then tried the 880 and I was bottoming the differential against the chassis. I had the 860s form some test I did on my old 2000 E350 and decided to give them a shot.

The only difference the length of the radius arm is going to make, is in how far the axles move forward and aft for a given vertical displacement. It will have no effect at all on the spring rate or spring force.

The different in geometry and behavior between the original 2WD suspension and a radius arm with solid axel is quite significant.

• With solid axle and radius arms, the spring work in the same distance from the pivot point than the wheel. From under the front seats to the axle. Articulation longitudinal to the centerline of the vehicle.
• With Twin arms, the pivot point is under the engine. The distance from the wheel to the pivot point is longer than the distance from the spring to the pivot point. Articulation is transverse to the centerline of the vehicle.

The same spring will give a softer ride and higher lift on a 2wd van. I tried the 860s on my old 2wd and rode like a pogo stick and the lift was too much. I use those very same springs (860s) on my 4x4 and I love the rate and height. Both vans have the 5.4

 

[McGuyver]

I did some calculations, but I've never weighted my van yet. I tried all three. I went with the 880s first since this was the general consensus. Too stiff, good height. then tried the 880 and I was bottoming the differential against the chassis. I had the 860s form some test I did on my old 2000 E350 and decided to give them a shot.



The different in geometry and behavior between the original 2WD suspension and a radius arm with solid axel is quite significant.

• With solid axle and radius arms, the spring work in the same distance from the pivot point than the wheel. From under the front seats to the axle. Articulation longitudinal to the centerline of the vehicle.
• With Twin arms, the pivot point is under the engine. The distance from the wheel to the pivot point is longer than the distance from the spring to the pivot point. Articulation is transverse to the centerline of the vehicle.

The same spring will give a softer ride and higher lift on a 2wd van. I tried the 860s on my old 2wd and rode like a pogo stick and the lift was too much. I use those very same springs (860s) on my 4x4 and I love the rate and height. Both vans have the 5.4

Good point on the center pivot. I overlooked that in making my comments. I was only comparing the lengths of the radius arm between the 2WD vs. The 4WD configurations.
My point was a simplified focus on the spring stiffness.
The additional pivots in the center will add another plane of rotation for the suspension that the 4WD configuration will not have for equal displacement of both wheels. However, unless the rubber bushings are imparting a significant difference in stiffness, then the differences between the 2WD and 4WD configurations are only kinematic in nature. Should not effect the spring force or spring rate. I suppose you might see some change in stiffness due to geometric nonlinearity over large displacements, but I don't think this is going to be detectable for small displacements.

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[b. rock]

Well not to go down that rabbit hole, but that's the larger question that was hidden in my comment - the leverage ratio changing throughout the travel will definitely make it feel different with the same spring, even though the spring rate/spring force hasn't changed. The whole 3 dimensional suspension analysis is beyond me but I've spent enough time looking at and riding various mtb suspensions to know that the kinematics of the linkage very much matter. Especially since some will be tuned to a progressive spring and some to a linear spring. I'd still love to find a suspension calculation program/analysis program and plug in the solid axle radius arm setups vs the short arm 4-links, but I'm guessing with the somewhat limited travel we are talking about they're fairly comparable. I-70 through the CO mountains is an atrocious highway, so it's very likely to see some sizeable impacts just driving down the road.

However, all that being said - it still comes down to just trying the 880s and seeing how it goes.

 

[McGuyver]

Have you tried searching for a suspension kinematics app? I'll bet someone's written one. Even if you have to pay a little bit of money for it, it might be worth it...

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[McGuyver]

I did a search and found this site:

Suspension Geometry Calculator

Quickly and easily see the affect movement has on your suspension set-up and adjust on the fly using the drag and drop editor.

www.racingaspirations.com

This is probably not going to do everything you had hoped to be able to do, but it's kind of interesting. I'm going to play around with this later when I have some free time.

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[kai44]

Hello all! I recently installed MGs kit on my van. installed a set of 880s but I'm having a hell of a time getting the top spring retainer to install. is there a different spring retainer or is there something else going on? sorry for this hijack

van info 2013 5.4 RB

 

[Raul]

Same spring retainer. Aftermarket springs use thicker gauge wire. I remember sometimes can be a pain. You may want to bent or conform the retainer a little bit.
I’ll be installing the front axle on my new van this week. Most likely I’ll be in the same predicament.

 

[kai44]

Same spring retainer. Aftermarket springs use thicker gauge wire. I remember sometimes can be a pain. You may want to bent or conform the retainer a little bit.
I’ll be installing the front axle on my new van this week. Most likely I’ll be in the same predicament.

Thank you for the info!