Why don't they make a "neutral" coil over spring?

[K85 Octane]

Curiosity has struck
Leaf springs have a neutral position, which are often close to ride height. Then you have droop and compression.
Captured coil springs on a truck (like the rear of my old C10, Jeeps I think, and the new Dodge rears) have a neutral position too.

Why don't coilovers have a neutral position? Car struts don't either.
I know mega droop is cool but it doesn't control body lean like leaf springs do. It also doesn't control the front end as you ascend a steep climb. Sucker just drops out, making the climb feel steeper and more weight transfer to the rear.

Coilovers got their start (I'm guessing) and shine from desert racing. Became popular for the high dollar sand rails and more affordable for the rest of the offroad community. Coilovers have always technically been on motorcycles and then ATVs etc. Vehicles for speed, tend to go in a straight line, and need quick rebound for the next compression cycle.


How come we can't take a coilover body and have ends that capture the spring? Then have a spring with a neutral position? Is that not easily "package-able" or just not "cool" enough?
Am I missing something here

 

[ktmoutfront]

Coil-overs are not designed to be static? If you keep them moving up and down rapidly, what you need won't matter. Go faster.

My front end unloads on any up hill. Took a little to get used to it. That is why I never did Hell's Gate or the Escalator until 2 years ago.

 

[Tnsejed]

How come we can't take a coilover body and have ends that capture the spring? Then have a spring with a neutral position? Is that not easily "package-able" or just not "cool" enough?
Am I missing something here

So, to do it, the spring rates have to be high. Pickups and whatnot are this way due to load carrying ability. Just the weight of the vehicle will not compress the spring much, hence the 'nuetral' area that I believe your thinking about, and the need for captured ends.

I'm far from knowing everything but here's my half a cent.

With coilovers the current trend is to figure out how to get the solid axles to drop out quick enough for high speed. So preload is key. Have to push the axles down. By preload we mean compressing the springs on the coilover body before its ever mounted on the vehicle. The springs do nothing more than hold the vehicle up, everything else is valving and geometry.

With body roll there's some tradeoffs here. In fact there's a ton of them. Different roll centers do different things. Lets think about a truck without any anti-roll bars first. You can build your link geometry to have a truck with almost no body roll. The downside here is it works on both sides of the fence: That no body roll seems good, but it also means the suspension resists compliancy. When a wheel hits a bump the forces are sent into the chassis instead of the suspension soaking it up and not upsetting the chassis. We want the latter, we want the suspension to work and the chassis to not move much.
We also have to think about loading tires during a turn and weight transfer etc. That comes into play as well.

So with that we can see that there are desireable areas of having a lower roll center, which will also mean body roll. Look at a TT, or Wades truck. He can haul ass and soak up alot of stuff, but the truck does some weird stuff in the rocks, its a tradeoff. We can't catch him in the desert, but I'll catch up in the rocks. I've only wheeled with Wade once, but i watched the truck quite a bit until he broke the panhard. With that said though his last comment is awesome because it shows something that I think is important. The chassis movement, as long as its predictable, sometimes isn't a physical problem.

Now if the chassis roll does become an issue we have an easily tuneable solution: sway bars. Its alot easier to tune a sway bar than changing your suspension geometry.

Front unloading. My truck will unload at certain times, and they all do it due to weight transfer. Its just how much is acceptable. You also have alot of geometry at play here as well. Anti-lift characteristics come into play as well. This area is where the lower COG shines. Something us trail rigs have a problem with. The interesting thing though, is that with the right geometry, staying on the throttle helps and will pull the front down. Just gotta have the balls.

Bottom line is I will take my soft springs over harder springs any day of the week. As soft as you're weight carrying ability will allow, with the correct preload. I did my backhalf with the provisions for an already engineered sway bar setup, but I have not put it on yet. I just put on my sailors hat and let the bitch roll.

 

[Fastereddie]

The only input I have is on the front unloading. That’s why you’ll see guys suck their front end down with their winch.

 

[K85 Octane]

All great points but I suppose it’s the trade offs that have me thinking about coil overs and links. I would like them for my truck, don’t get me wrong, but their short comings as a rock crawler are undeniable. By the time you sway bar both ends and suck down winches etc etc, it’s something you start to wonder about.

I think the best part about these setups are the links, not the coil overs. Links over leafs are much more tuneable, controllable, and durable. If there was a “rock crawler edition” coil over I think it would undoubtably have a captured spring.

How about 2 sceneries. (All in good fun)
These are not “be all- end all” for slower off-roading but would represent a lot of conditions seen on the trails.

2 Blazers exactly the same, except one has links and the other on leafs, begin climbing a hill that increases in slope as you go. Think “Where Eagles Dare” gatekeeper but continuing. Both in double 4L. Both about 6” lift, full body, stock WB. Out of the 2 trucks, who makes it up the slope farther? And, which one has a better chance of flipping over?

Since a longer wheelbase truck would benefit in the last scenario over a shorter Blazer, here is scenario #2.
2 long (over short) wheelbase trucks are driving 90* on a hill that increases in slope as they drive. Let’s say driver side is the high side, cause that’s scarier lol. Which of the 2 trucks will flop sooner? The link truck or leaf truck?

Sucking the front down with a winch and sway bars are not allowed, since the leaf truck doesn’t use them.

All hypothetical.
Just wondering why it can’t be done or why it hasn’t already.

 

[K85 Octane]

I can see the leaf truck hopping or chattering as it goes up hill, more than the link truck, but the benefit isn’t the shocks, it’s the links. Throw some antiwrap bars, front and rear lol, on the leaf truck.

 

[Hogback Fabrication]

I would like them for my truck, don’t get me wrong, but their short comings as a rock crawler are undeniable.

That's pretty much 100% the opposite of my experience, a well setup linked/coilover will outperform leaves in the rocks. Every time.

Sucking the front down with a winch and sway bars are not allowed, since the leaf truck doesn’t use them.

Not to say that links/coils can't climb anything without the suck down winch, but excluding them isn't really fair. You could put a sway bar and suck down winch on leaves if you wanted, but as mentioned, generally less common because the stiffer spring rate means they unload/lean less.

 

[K85 Octane]

Oh, I would take a link set up any time going flat over giant rocks. I’m sure my trucks frame would appreciate less twist as well. The coil, being softer, would make it much more pleasurable. And I concede that a captured coil might have a stiffer uptravel than a standard coil. It is doing more with half the amount of coils. I get all that but you have to question everything. Why a captured spring wouldn’t make a link system that much better?

 

[Hogback Fabrication]

So spring rate is what you're saying makes them climb poorly? Again, with really soft coilover springs, the suck down winch helps a ton. That's not cheating, most use the winch that's already on the front anyway.

Or, what if you're using a coil that has a similar rate to the leaf spring?

 

[K85 Octane]

Well, even in the other scenario, going across the hill, unless a sway bar is used the link setup would seem to want to tip over sooner. Winch would help there.

Hmmm yes, I suppose a similar rate as a leaf spring. Obviously that would be higher than regular coils now, but it would help keep the suspension closer to the chassis and not in auto-droop

 

[Tnsejed]

Well, even in the other scenario, going across the hill, unless a sway bar is used the link setup would seem to want to tip over sooner. Winch would help there.

Hmmm yes, I suppose a similar rate as a leaf spring. Obviously that would be higher than regular coils now, but it would help keep the suspension closer to the chassis and not in auto-droop

It would seem that way, but it is not necessarily so. This is not a spring rate thing, but a geometry thing. Sure if you made your springs at 10,000inlbs it wouldn't body roll and you'd end up with just a standard cog roll. I think the biggest thing here is understanding the way that roll takes place. When the body roll happens the cog will move downhill closer to the downhill tires, but not by a whole lot, and that amount is determined by the geometry (which leaves also have). Theoretically you can make a vehicle that tilts toward the uphill side.

The important thing here is that tire loading can take place with body roll, and that can help you stay on the obstacle, instead of sliding off. So sometimes it can be a good thing.

Another very important thing is driver feedback. You don't want something that is good one second, and after only a half a degree change rolls over. You want good feedback and you want it docile on a sidehill. A truck with insanely stiff springs would give you no feedback until it was too late. Not to mention those super stiff springs don't keep tires on the ground etc...

 

[K85 Octane]

I completely agree with the geometry of a link set up helping to fight the movement of the chassis. Feedback is very important. Folks that wheel their trucks often and have pushed them to those tipping points will understand more what’s going on underneath them. Coil overs are cool, just thinking if there is a better way.
Problem with a “better way” is that it might make a set up TOO specific. I would like to see a captured spring in a coil over for rock crawling, but I know there would be “go fast” cons.

 

[Stephen]

There's not a better way.

What you're dancing around with is the same as a running a coil with a shock just like every jeep since the TJ, XJs, Dodge trucks, etc. If you spring the truck light enough to get 14" of wheel travel, it doesn't matter if it's a spring that is separate from the shock or not, it will act the same.

What you're seeing with leaves is real and easy to see on the Escalator. Stiff rigs can drive wrong and get away with it because the weight of the front axle will pull the front end down and you don't tip backward. Something with a lot of droop will let the axle follow the terrain but not pull the front of the truck down with it and you tip back. But this isn't because of coilover or coil spring or leaf spring, it has only to do with spring rate and spring rate relates pretty directly to available wheel travel.

If you have 1200lbs to hold up on one corner of your K5, you can do it with a stiff spring (coil or leaf or even torsion bar or air) and maybe have 6" of total travel. Spring rate will be around 400#/in. Or you can do it with a soft spring and have 14" of wheel travel and have maybe 150#/in spring rate. Again it doesn't matter what the spring system is, the truck will react the same. A really soft leaf spring will push away on a hill similar to a same leaf coil spring.

What you're seeing as a "neutral" position on a leaf is only there because the springs are so stiff that they axle will pull them down once they get to their free arch droop position. You can have the same effect on a coil if you capture both ends of a stiff spring. Mostly when coil springs are too stiff you see it in the coil coming loose from the top perch and sometimes they just fall out.

Ways to make a rig climb better or sidehill better while still being sprung proper (soft):
#1: get weight low. Keep rig ride height down, pack weight low on the rig, and keep it light as possible overall. CG height KILLS climbing. Center the weight in the rig for best performance on climbs and drops.
#2: repeat #1, it's a big deal.
#3: Once you've exhausted that avenue, it's time to tie the axle to the truck. When guys running super light hard core cone dodging rock buggies with WAY fewer compromises than we make on trail rigs run suck down winches, it indicates they are not bandaids, they're tools. A pair (or one) of limit straps that you can pin in place at ride height to hold the truck and axle together may be worth it for you. There was a time I had a single center strap that was about 6" long with quick pins that I put in place before big climbs. Swaybars fall in this catagory and are less important sometimes with a really low CG and with very specialized link geometry.
#4: There are gains to be made by playing with suspension geometry that really only apply to link suspensions and making something that climbs really well probably compromises other places so as long as it's not really wrong, you're probably not going to find a lot here. Just make sure that it's not really wrong or if it is make sure you know why (sometimes it's for higher reasons like keeping the driveshaft alive) and know how to drive with it.

It's not worth beating yourself up and compromising performance on 95% of the world to make a rig really climb and sidehill like a champ. We used to do dumb shit like run a ton of rebound damping in the shocks to try to make them climb better and thank goodness that went away. I have a King valve tag in a file here that specs a 20 stack on rebound. It rode TERRIBLE and still didn't climb that well. For comparison a more typical valve stack uses .010" shims and is multiple times softer. For a good comparison you can take a ride in any IFS truck with the torsion bars cranked till there's no more droop or put a limit strap on your existing suspension to keep the suspension from drooping at all. Good for lowering the CG of your truck since you're attaching 1000# to the chassis in about the lowest point possible but terrible for everything but climbing.

I forgot about running water in the tires. You can do that too and it is awesome when you tie the axle to the chassis but once again you're probably not going to like it for the large portion of the world that isn't past your climbing limits with the rest of the tricks in play.

 

[Hogback Fabrication]

^^^^ I think this guy explained it better than me

But soft springs are soft, stiff springs are stiff, doesn't matter if they're leaves or coils.

If you're at the point of stretching a spring past "neutral", you're definitely on the stiffer side. It limits travel on the droop side just like it does on compression.

Having ~20 years of rock crawling on both, there's no comparison. Leaves are cheaper/easier but for performance, links and some form of coil will far outperform them every time.