QCVette

Yes they are different.

The sway bar rotates in the bushings the spring does not.

So for a sway bar, when both front wheels rise (compress the shocks) the sway bar does not create any force on the wheel (control arm), but rotates within the bushings. There should be little resistance from the bushings, but in practice there is some but usually slight.

If the sway bar only has one front wheel rise (or fall), then the sway bar twists to keep the other front wheel at a matching height. When unequal wheel movement occurs the sway bar acts as a torsion spring.

However the leaf spring is simply a spring. It always pushes down on the wheel (control arm). Depending on how much the wheel rises determines how much force is applied by the spring (spring rate). It does not rotate or reduce the force based on what the other side is doing.

Kevova

Coil overs are about tune ability and independent suspension articulation. The transverse spring was about weight reduction at low cost. IMO if you're serious about a drag only, you should plan on coil overs. The stock front spring is what it is; not easily adjustable in regards to adjusting weight bias. Drag cars can twist during holeshot stabilizer bars can cause tire to lift as torque loads opposite tire. Without the bar the spring pushes both wheels down. When drag cars get out of shape some great driving may save them, but the aren't intended to corner.

BOOT77

ADJUSTABLE coil overs are better if tuned right and because they CAN be tuned to suit a certain customized car unlike standard production springs. If the article even discussed or compared adjustable coil overs it might read diff. I find ignorance and close mindedness HILARIUOS. Learn how to operate the zoom function if you use explorer.


Yup I thought I said ACT LIKE, not mono springs are a sway bar. Sure I said they connect the same but I didn't say they are EXACTLY the same.

Tom400CFI

That is a terrible method for determining effectiveness of a system. "If it's so good..."

DRM and others make them for two reasons:
1. People like you, who don't "get it" how a transverse leaf spring works, are willing to give your money to people like DRM for a different style spring...that does the same thing (minus the sway bar effect).

2. People who DO "get it", how springs work, and track their cars regularly, want adjustable preload for corner weighting and ride height, as well as a readily swapable, cheap spring unit for changing spring rate. Neither of which you can do readily w/the stock spring.


Removing the sway bar will remove a few pounds (15ish?) from the front of the car, as well as removing the friction from the sway bar system. Over all, it will help very slightly w/weight transfer. IMO, removal is not worth it on a street driven car....totally worth it (along w/a plethora of other weight reducing mods) on a drag track only car. I would not be "afraid" to remove the front bar, then drive to and from the track w/it. Not at all.

Gene D

This has been discussed for years.
Sway bars are for 1 thing. To speed up side to side weight transfer to limit body roll or twist.
Let's say you take a 4000 lb. car that has 1000lbs on each tire while it is sitting still into a corner at 35 mph. And the car has no sway bars.
That car will transfer say 200 lbs of weight to each outside tire.
The car will compress the outside suspension 1 inch and the inside will lift 1 inch.
So outside tires will have 1200 lbs on them, inside will have 800lbs on them each.
Take the same car and add equal size bars to the front and back.
Take same corner at same speed.
200 lbs will still be transferred. Outside 1200, inside 800.
The outside suspension will only compress say 1/2 inch. Inside will only lift say 1/2 inch.
A sway bar becomes part of the suspension as soon as the body rolls.
Yes, mono leafs and sway bars are both bolted to frame and Control arm... but one is anchored to the frame the other is anchored to the other control arm. They do entirely different things.
Where things get tougher to figure out. if you have a sway bar in only the front. The rear will try to twist the full 1 inch, but the front will try to stop at 1/2 inch.
So the front outside will get some of the rear weight and the front inside will lose some from this. And the rear will have less transfer.
This is very good if you are trying to accelerate out of a corner.

This has been played with for years.
Lots of circle guys run without bars. They just use a little tighter outside spring setup or roll a little more.

The good for sway bars is less roll. so steering alignments stay closer. Bump steer stays a little closer. Car does not roll or sway as much.
The bad for bars is weight and a chance to bind your suspension.

If I was driving my car to the drag strip...sway bars would stay at home. I don't think a little more body roll in a corvette will change it too much.

Tom400CFI

Guys, you're confusing solid axle car physics w/IRS car physics here. Solid axle cars will "twist" when launching due to engine/trans tq. The engine trans of a stock 'Vette could make up to ~1000 lb/ft of tq in 1st gear. Where doesn't that tq reaction go? Into the frame. What happens to the frame? On a solid axle car, it tilts the frame on the car's suspension. Hence, the BIG sway bar on the rear of solid axle, fast drag cars (as well as staggered rear spring rates, sometimes).

But what we have here is an IRS car. Totally different forces at play here. The reaction tq from the engine/trans is resolved through the frame rails and the batwing/diff housing. That reaction tq from the engine/trans never makes it to the suspension or tires.
The fastest IRS C4 car on these forums (rklessdriver) used stock monoleaf springs in his car and no sway in the front. His car launches straight and flat (no twisting).

.

ddahlgren

Tom400CFI you have no idea what I know and don't know. I know enough about suspension to get a 3200 lb. IMSA GT1 car around Daytona at 1:48 and 206 mph. down the front straight. The previous genius had it running 2:05. Similar outcomes at different tracks as well. You affect weight transfer with suspension geometry. There are no secret springs, they are support the weight of the vehicle and everything else is geometry.

The GM spring commercial makes some assumptions that are false. The most glaring one is the spring displacement at the mounting point. If the spring is mounted solid this can't happen. The fantasy starts there and never gets any better. When Pro stock cars run a semi-elliptical fiberglass front or rear spring I will become a believer.

BTW I have the fastest green 91 C4 coupe with an L98 in the entire town of 4000.

Tom400CFI

Sure you do. That's why you cite an aftermarket vendor producing a suspension option as "proof" that the stock design is no good.



And this is (just one place) where you go awry. The front spring isn't 'mounted solid'. The rear spring is mounted solid and therefor doesn't/can't provide the effect we're discussing here.



Again...using anecdotal "evidence" as proof. WTF? A prostock car isn't likely to use a composite mono leaf spring for the same reasons that I cited earlier; lack of adjustability, and the suspension configuration isn't conducive to it.



Good for you.

RichS

I haven't had a front sway bar on the GS for 15 years. I removed it to take weight off the nose, and better weight transfer on launch. Never had a issue driving on the street not having it. It also helped a tiny bit for the 60'. Just don't drive like a maniac going to the track, simple!

blackozvet

I love these arguments, especially when Tom takes on 2 opponents !

But the more I learn about suspensions, the more inclined I am to call BS on those sort of articles talking about leaf springs with "S" bends in them transforming themselves into sway bars ??

Anybody who has pulled front springs in and out of these cars will know that they are well and truly clamped in the middle, there is no S bending going on, it doesnt matter how wide or narrow you make the bracket, the centre of the leaf that is clamped in there is going NOWHERE. The leaf has a limiting bump stop that stops it bending any more than the compression travel of the shocker, about 2.5" roughly, making it compress no more than horizontal across its whole half length.

as for the leaf having 80% more roll stiffness than a coil spring of the same rate, that is just ludicrous ! every spring has a rate in lbs per inch, and thats how much force it takes to compress it 1 inch. How does a leaf suddenly gain 80% more stiffness at the same given rate ?

we all know that for every 10 degrees you lean a shock and or spring over, it loses rate, so how does that bode for a spring that is horizontal ?
A vertical coil spring is much more efficient than a horizontal spring. That is why "performance" or "track rated" leaf springs for the c4 come in 1000 - 1200 lb rates when a z51 front spring is rated in the 600 plus lb range. That is why people who change to coil-overs are amazed at the sudden difference.

as for the talk of leafs being able to do away with sway bars, as somebody mentioned earlier why then do people run 30 and 32 mm bars on these cars, that is a fair bit of spring rate being introduced to resist roll. there are a lot of other performance cars that weigh more than the corvette running similar size bars.

MatthewMiller

Wow, interesting arguments going on here. First, back to the OP. As Tom noted, a car with an IRS like a Corvette is not going to experience the twist and right-rear-tire lift that a solid axle will cause at launch. So the swaybar removal thing is probably not very useful. What you really need to do is corner-weight the car and make sure both rear tires are sharing equal amounts of load. If not, you can actually use adjustable-length end links on the front bar to adjust that. But it's much easier to just adjust the threaded bolts on the ends of the rear spring to equalize it. OTOH, driving on the street with the rear bar connected and the front removed or disconnected is asking for trouble. You will have a car that is very prone to oversteer. It's easy to say "Just don't lose it," until you have to panic stop or do an emergency lane change. I wouldn't do it. I guess you could remove the rear bar, too, to balance it out. But as suggested, it would be a lot safer to just drive to the track with the bars connected and then disconnect one side of the front bar once you're there if you want to try this.

As far as the leaf springs acting as sway bars, I don't buy it. It is true that sway bars are a type of torsion spring, but they only act in roll: they provide no additional wheel rate in pure dive/heave (i.e., when both wheels move the same amount in the same direction). Springs provide the same wheel rate for all independent wheel movement, regardless of what the other wheels are doing. This was already noted earlier. If the transverse spring were only mounted at one point in its center, and had freedom to pivot around that mount, then it would actually act the opposite of a sway bar: it would only provide wheel rate in dive or heave and would not resist roll at all*. But that's not the case: it is attached to the frame at two separate points that keep it more or less rigidly set parallel to the frame regardless of how either end of the spring is displaced.

**

The give in the rubber mounts technically provides a teeny amount of freedom to pivot around an imaginary center mount, but that is surely negligible. And again, any of that movement would actually cause it to resist roll less. The easy way to test this would be to mount a frame solid and then move only one wheel into compression and rebound and see if you can measure significant movement or load for the wheel on the opposite side. This is the kind of thing engineers use a post rig to measure. But without sway bars, you won't find that a left wheel reacts to displacement of the right wheel or vice versa.

*I had to edit to correct myself, because I originally had this backward when I posted it!
**I know that's a pic of the rear spring, but it's hard to find a clear pic of the front mounts. But they are similar.

Tom400CFI

Someone needs to go on a fact finding mission....w/the lower arms removed, jack one side of the spring...see if the other side is affected.

This is all discussed in "Corvette from the Inside". From Dave McLellan's perspective, the "anti rollbar effect" exists to the extent that the original plan was to go w/o any sway bar at all, in front. They ended up using a bar, but you'll notice that it is quite a bit smaller than the bar in the front of an F-body, as a comparison.

MatthewMiller

The F-body comparison is not applicable though, because the roll centers and mass centers are so different, especially in the rear. And of course, just changing the length of the center section and arms of the bar make big difference in how much diameter is required to create a certain wheel rate in roll. OTOH, you won't find too many similarly-dimensioned sports cars with Camaro-sized sway bars, even though they all have coil springs.

This could easily be mocked up in a scale model simulation. Maybe one of these days I can find the time to do this. My kids could learn something from an exercise like that.

Tom400CFI

I agree that they're not the same car, but they're pretty similar as far as dimensions, CG height, width, handling goals, etc. Also, in the book, IIRC the Camaro is referenced as a comparison to the 'Vette WRT the sway bar size. I was only talking about the fronts of both cars, since the rear of the 'Vette doesn't have this feature (and does have a similarly sized rear bar to an F-bod).



Heck yeah. That would be a great experiment for a kid to participate in.

MatthewMiller

Understood. But the rear suspension and weight distribution really affect how the front roll stiffness is specified. For solid-axle F-bodies (understand that 5th and 6th gens are IRS designs), the rear roll center is much higher than on a C4. That means that in terms of spring and sway bar rates, you will have to have a much higher front rate for roll compared to the rear. But because it's more front-heavy, it's not desirable to achieve that with stiffer rear spring rates (for ride compliance reasons). So they were always going to achieve the roll rate bias with a big front sway bar.


It is possible to make a lateral link that puts the RC really low, even below ground. The Shaw Link (I really hate bringing that up as an example of anything good!) for Fox and SN95 Mustangs did that. Those who installed it found in short order that they had to really reduce front swaybar sizes and/or increase rear spring rates a lot to make up for the increased understeer.

ddahlgren

For this test to work the frame has to be clamped rigidly to a fixture and a scale put under the free end and a strain gauge on the compressed end. This is not a 2 car garage test.

Second the leaves between the 2 mounting points are the greatest rate as thickest.

Third engineering is often over ruled by both styling and bean counters. Styling wants the look and gave us the flexy flyer targa roof and the bean counters did not offer more money and time to make it work. Bean counters also love to reuse existing tooling and production methods in place to make a part a zero increase line item.

If it was for weight and simplicity a sleeve hat and spring over the shock is lighter simpler and easier to assemble at OEM levels. Bilstein could have easily done it for GM as an everyday operation in their plant. Again no money for engineering or updates to the mounting points for them.

99% of all decisions are made by stylists and bean counters.

An independent review by an engineering firm that specializes if performance suspension design would be much more enlightening than a GM rep.

Lastly the point of independent suspension is just that. One wheel affects the others as little as possible. Anti roll bars are for fine tuning of front grip vs. rear and ride quality vs. body roll as well. They might as well be called compromise bars LOL for a street car and a tuning aid for a race car that ride quality is second to lap times.

If you look at the target audience and use of the car it is designed to be a sporty touring car with good enough handling to please 90% of those unlikely to exceed the speed limit by X2. It had to be sold for a price that can support a profit to produce, hence the bean counter influence. This is unlike a exotic import that engineering designs the chassis and drive train and turns that over to the stylists and coach builders to put a body on it as long as no aero compromises are made. Same for interior. When done they tally up the build add profit and that is what they cost. The reason exotics sometimes sell less than 1000 a year rather than 1000 a month.

This is one of those conversations that can go on forever as there is no concrete proof the GM claims are correct with any reasonable testing, if there is lets see it. If it really works so well what is the other car at any price point that uses it any price point?

Tom400CFI

That's not true at all. Jack and stand the car. Remove LCA's. Spring will be totally relaxed at that point. Place a jack under one side of spring, start jacking, observe other side. Other side should rise as you jack the loaded side if theory proves correct. Pretty simple stuff here.


What's this got to do w/springs? Leaf or coil...style is the same. Transverse leaf wasn't a existing part or tooling, so....


So wait...what are you saying here? Earlier, you said they used the monoleaf as a cost saving measure (which I have no doubt that there is a cost benefit to it)...now you're saying it could have been done cheaper ("no money for engineering") to use coil overs? Which is it?? Still not sure what this has to do w/how the spring works. (?)



More Recently, VOLVO XC90



As well as in the S90;




At a lower price point, GM has used them previously. They may still be...I didn't look too hard.






Even our 1910 Hupmobile and Henry Ford used 'em






Of course I'm joking with the old cars, but there are just a few examples of "other car at any price point that uses it any price point?"
...At "any price point".


.

rocco16

You are wrong on this one, Tom.
Engine torque will cause the chassis to torque in the opposite direction regardless of the type of suspension...or even if there is no suspension.

To the OP; drive sensibly without a front sway bar and you won't notice its absence.

ddahlgren

Well short I think of the Hupmobile all the rest GM go figure and all very boring cars at best.

You can win your fantasy and no longer a player it is like arguing the 2'd amendment to a democrat LOL...

Have fun with the fantasy that is off the wall.

Engineering and logic have left the room from what I can see.
Dave

Tom400CFI

Nope. I'm not wrong. You're wrong though and you're wrong, b/c you don't "get it" how things work. In reality, you don't "get it", b/c you're not thinking the whole thing through.
Let me ask you this; Does a Honda Civic....or does any transversely mounted FWD car "tq in the opposite direction"? The answer is NO. It doesn't. Why not? "Obviously" that is because the engine is transversely mounted and so is the trans, so no tq acts on the car's body, side way or twisting it on the suspension. The entire engine/trans/diff is one, single unit and the only tq it exerts on the suspension is opposite that of wheel acceleration direction. IOW, if the engine/trans/diff assy is accelerating the wheels forward, the reaction tq will "rock" the car rearward on it's suspension...but not side to side. The Corvette is not a Civic, but we'll get back to that in a minute...

What about the Corvette? You'll assert, I'm sure, that the engine/trans is longitudinal. Stop thinking about just the engine. The engine/trans assy makes the tq (up to ~1000 lb ft in 1st gear). There is an "equal and opposite reaction"...where does that go? Into the frame. Then what? Does that tq disappear? No, you're sending ~1k lb tq into the frame in a CCW direction, as viewed from the front of the car and also ~1k lbs into the diff in a CW direction, as viewed from the front of the car. What do you suppose the diff housing "wants" to do? Well, if it wasn't bolted to the frame, it would simply rotate in the same direction as the driveshaft is turning it, w/o turning the wheels. But, it IS bolted the the frame through the widely spaced batwing bushings so that ~1k lb tq force is sent where? Into the frame.

So you have the engine putting ~1k lbs tq into the frame in a CCW direction, as viewed from the front of the car...and you've got the Diff putting ~1k lb tq into the frame in a CW direction....what happens? The frame is more than strong enough to handle this force, the tq cancels itself out and the whole system behaves just like the Honda; as one single unit that only imparts tq on the axle shafts and a reactive tq on the body trying to rock/rotate it rearward.

To help visualize the flow of tq path more clearly, consider the C5^. Even thought it has a longitudinally mounted engine/trans, the engine/trans/diff is all bolted together in one, solid, rigid assembly just like the Honda example (except spread out over more space). How can it behave any differently than the Honda? It can't. The engine is still longitudinal, but the tq is resolved through the tq tube so net tq "twisting" on the chassis is essentially "0". The C4 (and C3 and C2) is the same, except the the task of resolving engine and diff tq's is resolved through the frame rails....not the tq tube and not in the suspension as you'd see in a Chevelle, Camaro, etc w/a solid rear axle....and where the "twisting" lore comes from.


THINK about it. READ THIS