'09 Ram: All-Coil Suspension

[SJ_GTI]

It would seem that, as with all things, you could make either strong enough to suit your needs, however I suppose there is a correlation between beefiness and spring rate.

To me the issue seems to be which is better for heavy duty performance at a given price? If you have $100 to spend on procuring the heaviest duty suspension component, would you choose leaf-spring or coil springs?

I don't know that much about heavy duty suspensions,but I doubt its as simple as you and gocougs are making it sounds.

Given the price, coils may very well be better at extremely high levels of performance relative to cost, but at more plebian levels leaf-springs may be the better option relative to cost. I don't know the answer, just explaining why the examples given do not really "prove" anything one way or the other.

[Tave]

Which brings up another point: If you're breaking front coil springs on Dodge Ram you are simply abusing the truck well beyond its designed intent. Way WAY beyond. It's quite hard to break a coil spring.

I'm sorry to mislead you. We break a lot of front shocks on the trucks. I believe I said that earlier. If I said we break coils coils I apologize.

If Dodge can can use rear coils without sacrificing hauling and towing capability, and it doesn't cost material any more $$, there is virtually zero detriment to the consumer.

Correct.

I also note the just recently the 4X4 F-250/350 went from leafs to coils in the front, and I also note that the Avalanche has always used rear coils, as have recent iterations of the Expedition, Tahoe, Durango, Armada, and other 1/2-ton based SUVs.

Right, the trend to civilize the ride quality of the truck market isn't new.

[Tave]

To me the issue seems to be which is better for heavy duty performance at a given price? If you have $100 to spend on procuring the heaviest duty suspension component, would you choose leaf-spring or coil springs?

I don't know that much about heavy duty suspensions,but I doubt its as simple as you and gocougs are making it sounds.

Given the price, coils may very well be better at extremely high levels of performance relative to cost, but at more plebian levels leaf-springs may be the better option relative to cost. I don't know the answer, just explaining why the examples given do not really "prove" anything one way or the other.

Exactly, that's all I was wondering too, and the point I tried to make to GoCougs about the Hummer, which also has an independent rear-suspension that performs just as well as a solid axle, but costs more.

[Eye of the Tiger]

Exactly, that's all I was wondering too, and the point I tried to make to GoCougs about the Hummer, which also has an independent rear-suspension that performs just as well as a solid axle, but costs more.

Coils can be used on solid axles, too.

[S204STi]

To me the issue seems to be which is better for heavy duty performance at a given price? If you have $100 to spend on procuring the heaviest duty suspension component, would you choose leaf-spring or coil springs?

I don't know that much about heavy duty suspensions,but I doubt its as simple as you and gocougs are making it sounds.

Given the price, coils may very well be better at extremely high levels of performance relative to cost, but at more plebian levels leaf-springs may be the better option relative to cost. I don't know the answer, just explaining why the examples given do not really "prove" anything one way or the other.

I wasn't trying to simplify it.  I think it's proven that for the price leaf springs are more effective, and I'm not arguing that.  What I am arguing (see my post on previous page for reference) is that there isn't necessarily a direct correlation between cost-effectiveness and durability, since as I pointed out I used to replace leaf springs on a regular basis on Frontier pickups.  I don't remember having that issue with coils.  Both can be engineered to a certain point to accomplish a goal.  As the article points out it does limit the ultimate load (or was it tow?) rating of the vehicle, but not to the point that it would impact a 1/2 ton truck.

[Rich]

Are you intentionally being difficult?

He always does this

[Soup DeVille]

To me the issue seems to be which is better for heavy duty performance at a given price? If you have $100 to spend on procuring the heaviest duty suspension component, would you choose leaf-spring or coil springs?

I don't know that much about heavy duty suspensions,but I doubt its as simple as you and gocougs are making it sounds.

Given the price, coils may very well be better at extremely high levels of performance relative to cost, but at more plebian levels leaf-springs may be the better option relative to cost. I don't know the answer, just explaining why the examples given do not really "prove" anything one way or the other.

Part of the leaf spring advantage is that the leafs also locate the axle- the traditional hotchkiss drive only uses leaf springs an nothing else, while coil springs need trailing arms or other components to physically locate the axle and hold it in place.

The downsides of this are:

If you really do break a main leaf spring, your axle falls off; if you break a coil, the suspension slumps and may even ride on the stops, but the axle remains more or less in place.

On a leaf spring, it also means the suspension "toughness" is directly related to how strong the leaf spring pack is; and therefore leaf springs simply need to be stronger; and therefore stiffer in many cases than you really want for the suspension to work properly just in order to due their other job of holding things together.

Conversely, on a coil spring suspension you can have a relatively soft progressive rate spring attached to a completely solid, bullet proof suspension.

[GoCougs]

Exactly, that's all I was wondering too, and the point I tried to make to GoCougs about the Hummer, which also has an independent rear-suspension that performs just as well as a solid axle, but costs more.

The new versions of the Expedition, Armada/QX56, Sequoia, and probably other 1/2-ton based SUVs also use IRS. They don't cost appreciably more than their previous generation live-axle predessors. They tend to weigh a bit more than their truck cousins, so they don't have quite the towing/hauling performance, but it's at about 80%.

Each design can be as reliable/durable/strong as it is designed to be. One can design wimpy leafs (think a '74 Pinto) or beefy coils (think a 50,000 lb HMTT).

When it's all said and done however, coils are better all around than leafs - less unsprung weight, no sliding leafs to bind or catch, better variable rate range, and probably some other stuff.

This is a very good move by Dodge. Will it be a game changer? A bit. I surmise however that other truck makers all ready have coils and/or IRS on the drawing board for future generations - especially considering that many already have coils/IRS under 1/2-ton based SUVs already in production.

[sandertheshark]

When it's all said and done however, coils are better all around than leafs - less unsprung weight, no sliding leafs to bind or catch, better variable rate range, and probably some other stuff.

That's an excellent and well-supported qualitative argument there Cougs.

[GoCougs]

That's an excellent and well-supported qualitative argument there Cougs.

Rather than a personal attack, howzabout a technical counter argument to both mine (and SdV's posts)?

[Submariner]

Actually, M1s are damned dangerous vehicles to be in an accident in.

Of course, the tank itself is just fine, but the occupants can be beaten up pretty severely real easily.

Would you prefer to be the man in the pancaked Aveo?

[Soup DeVille]

Would you prefer to be the man in the pancaked Aveo?

If I'm taking an Aveo up against an M1, I'm screwed from the get-go.

[etypejohn]

Quite the opposite - that they cost a lot lends credence to coil suspensions, in that those vehicles are specifically very heavy and/or harsh duty. Coil spring design is about as basic as it gets - most domestic cars up until the '80s were rear-leaf sprung, including the performance variety (Mustang, Camaro, Challenger, etc.) - now none of them are.

What!!!  The Corvette isn't using a rear leaf spring anymore?

[Secret Chimp]

What!!!  The Corvette isn't using a rear leaf spring anymore?

It is, but the Corvette uses a transverse leaf spring (think Model T front axle)

[etypejohn]

It is, but the Corvette uses a transverse leaf spring (think Model T front axle)

Of course it does, but it's still a leaf spring.

[280Z Turbo]

Of course it does, but it's still a leaf spring.

Fiberglass, not steel. Maybe even carbon fiber, but definately not steel.

Fiberglass leaf springs are superior to steel ones since they don't fatique over time.

[93JC]

More importantly the leaf springs in the Corvette are not used to locate the axles as they are in a traditional Hotchkiss drive: they're used in almost exactly the same way as a comparable double A-arm coil spring suspension.

[GoCougs]

What!!!  The Corvette isn't using a rear leaf spring anymore?

That's why I like etypeJohn - he keeps me on my toes.

[GoCougs]

More importantly the leaf springs in the Corvette are not used to locate the axles as they are in a traditional Hotchkiss drive: they're used in almost exactly the same way as a comparable double A-arm coil spring suspension.

Not exactly. It does do double duty as an anti-roll bar, which is quite problematic when it comes to handling (that is, simultaneously enduring two disparate stresses - torsion and bending - from two disparate actions - body roll and wheel movement).

[93JC]

Well... sort of, I guess. Hypothetically the same 'problem' presents itself in a different way in any car with an 'indepedent' suspension with an anti-roll bar: the movement of one wheel will affect the movement of the other, through the anti-roll bar.

I mean, really, when you get down to it an anti-roll bar is essentially a torsion spring deliberately set up to connect one wheel to the other for the sake of resisting the roll moment in a turn while sacrificing a small amount of suspension independence. The only specific 'problem' with the Corvette's suspension that I can think of is that the monoleaf is used in such a way that it must be stiffer.

But then again that's basically what you just said, isn't it.

*sigh*

Nevermind.

[GoCougs]

Well... sort of, I guess. Hypothetically the same 'problem' presents itself in a different way in any car with an 'indepedent' suspension with an anti-roll bar: the movement of one wheel will affect the movement of the other, through the anti-roll bar.

I mean, really, when you get down to it an anti-roll bar is essentially a torsion spring deliberately set up to connect one wheel to the other for the sake of resisting the roll moment in a turn while sacrificing a small amount of suspension independence. The only specific 'problem' with the Corvette's suspension that I can think of is that the monoleaf is used in such a way that it must be stiffer.

But then again that's basically what you just said, isn't it.

*sigh*

Nevermind.

The issue I see isn't necessary one side affecting the other - I'm making the assumption that the transverse leaf is bolted stiff enough in the center such that there is a stress discontinuity (no "cross talk"), and hence it acts as two separate springs. If this is not the case, the Corvette suspension is a real mess.

The issue is that on the same side, half the spring is being asked simultaneously to counteract the affects from body motion (torsion) and wheel motion (bending). I will also add however the Corvettes still have sway bars, but they are smaller than you'd expect.

Two different stresses with two different consequences on suspension performance. It's too much compromise IMO.

[93JC]

The issue I see isn't necessary one side affecting the other - I'm making the assumption that the transverse leaf is bolted stiff enough in the center such that there is a stress discontinuity (no "cross talk"), and hence it acts as two separate springs.

It's bolted at two points, as far as possible from each other (while still equidistant from the centreline).

If this is not the case, the Corvette suspension is a real mess.

I think the idea is that it's essentially fixed in the lateral direction while allowing for some movement in the vertical.

If you do that, the outside wheel in a turn should push the centre section of spring between the two mounting points down, which bends back up to meet the bracket at the inner wheel mounting, which pushes the inner wheel down, which aids in cornering, right?

I think I confused myself.

The issue is that on the same side, half the spring is being asked simultaneously to counteract the affects from body motion (torsion) and wheel motion (bending).

With two mounting points the torsional effects due to the body motion would be minimzed.

I will also add however the Corvettes still have sway bars, but they are smaller than you'd expect.

I would expect them to be smaller, as the spring acts as its own sway bar. I thought you just said the spring is being asked to be a spring (resist wheel movement) and a sway bar (resist body roll)?

Two different stresses with two different consequences on suspension performance. It's too much compromise IMO.

I don't think it's as much of a problem as you think.

But for the sake of shutting up critics they might as well switch to coils in the C7. Not because they're better, but because people think they're better, which is what really matters.

[omicron]

Our trees have green leaves.

[93JC]

Our trees don't have leaves...

[hounddog]

I still have yet to see a material technical criticism of rear coils.

Maybe Oshkosh Truck Corporation (uses coils on many, many of its heavy duty trucks) is all wet:

Coil springs cost less, are lighter, have almost no internal friction, and even take up less space.

However, they do not locate the axle and require a three or four link system to do the same job leaf springs can do without any assistance, often making the entire leaf spring suspension SYSTEM lighter.  They also allow more body drop than do leaf springs in heavy terrain, and under static load.

Leaf springs are modular, want more height?  Add a couple more leaves.  Want it lower?  Remove a couple leaves.

Leaf springs also help to reduce sway.

[nickdrinkwater]

So the Ram is soon going to have a more advanced suspension than a Mustang? 

That's not saying much, but yes, I guess...

[Nebtek2002]

Early 1960s GM pickup trucks, both 1/2 ton and 3/4 ton, used coil springs at the rear.

I still see these trucks in use as daily drivers.

[Pancor]

I won't be a detractor of either system, but the "R" racing 'vettes use coil springs on all four corners.  Does anyone know why?

[280Z Turbo]

I won't be a detractor of either system, but the "R" racing 'vettes use coil springs on all four corners.  Does anyone know why?

Adjustability.

Serious race teams may want to swap their springs out for different tracks and coilover shocks allow adjustable ride height.

[S204STi]

Adjustability.

Serious race teams may want to swap their springs out for different tracks and coilover shocks allow adjustable ride height.

As well as corner weighting.