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Do swaybars improve handling & cornering or not ?

M

MvM

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There is a thread about swaybars right here. http://www.nsxprime.com/ubb/Forum1/HTML/006368.html

From what I read there swaybars make you car handle better in corners because it will roll less. That would mean I can go faster in corners because the weight transfer to the outside wheel is less (car won't 'lean' as much on the outside tire). That would be a GOOD thing.

However, when I read the FAQ at http://www.nsxhelp.com/faq/swaystrutbars.htm
I get confused.

It states, quote:
(Swaybars will) "Increases weight on outside tires - decreases weight on inside tires"

Is this correct?? I thought it would be the other way around.
The FAQ also states:
"(This) is not a good thing for handling. The coefficient of friction for your tires decreases as more weight is applied. ...
If your car weighs 2000 lbs and 1000 is in front and 1000 in back, your cf might be .8 (example). Your total grip in front is 500*.8+500*.8. As you go into a turn, some of the weight in front transfers to the side so you may have 600 on one front corner and 400 on the other. However, at 600lbs, the cf may be only .7 and at 400, the cf may increase to .85. (Each tire has different values here.) Your total grip now is 600*.7+400*.85 which is 760. This is a decrease in total front grip. When you add stiffer sway bars, you increase the weight transfer to the outside which further decreases the cf for that outer tire and, therefore, for that end of the car."

Reading that I would actually loose grip and therefore my max. cornering speed would go DOWN instead of UP.
Can someone explain this (a bit) for me?
 
Suspension tuning is a black art. If you go by what one of the FAQ portions says, you'll find that Sway bars are bad. Another will tell you its good.

Sway bars do in fact lower the amount of weight on the outside tire. They also bring you closer to the "Rigid Axle" concept by limiting the movement between the two sides of your suspension.

BUT, Sway Bars also reduce your side to side motion and your body roll, thus making your car more responsive to steering inputs and more stable through high speed corners.

Andrie Hartanto might tell you that Sway bars are completely unnecessary. I think he can explain this for you if he reads this thread. Then again, in my opinion, sway bars are the only way to tune the side to side roll characteistics of your car separate from the front to rear squat and dive characteristics that the Springs and shocks will determine.

so...
basically...get sway bars. They're cool.
 
Hi Maarten,

I don't know whether you get more weight on the out or inner side wheel, but what I do know, is that body roll is reduced with sway bars. That alone gives you a more secure feeling while cornering. And if that is a fact I understand, the car gives me more confidence. So much confidence, that I go faster through corners and chicanes with stiffer sway bars than OEM.

The only (for me) important thing is, that you have to find a good balance in stiffness between front and rear. The more stiffer you make your rear in comparising to your front, the more oversteer you will get. That's why it is important, that you always choose for sway bars on which you can change the settings. Only than you can make a good setup with your suspension and wheels/tires.

Gerard

BTW I don't agree with Andrie. See the thread where we 're arguing about that
 
Hmmm. . .I got in trouble for saying that swaybar/antiroll bars reduce the amount of weight on the outside tire. I did some more looking into it and found that I totally misread the text (or did I read it all?) on sway bars. From what I remember and what makes sense to me is that, yes, sways do put more weight on the outside tire but aid in keeping the tires contact patch static throughout a cornering event. So there's a balance you want to achieve. The same is true for the "rigid axle" concept. That will come into play but only in extreme situations that, I think, you're very unlikely to achieve in your NSX. We don't drive off-road racing trucks and the amount of bound and rebound we need is certainly within the range for the effective use of sways. From what I understand, PD doesn't run a rear sway. This is designed, I would think, to give him fractionally less rear traction and to make his car more "rotation friendly." But understand, he's got a huge amount of mechanical grip (read: big ole' rear tires.)

Ok, I also thought that making the rear sway stiffer would increase traction thus making the car have an understeer effect.

I have Mark Johnson's street/race sways and think they're great. Certainly, I get more traction than when using the stock sways.

Someone else chime in here.

[This message has been edited by Ponyboy (edited 17 September 2002).]
 
Hmmm... *** I *** thought that the amount of weight transfer is simply a matter of physics. Go through a corner with a radius of x feet at y mph, then if your center of gravity is z feet above the ground, you can calculate the amount of weight transfer - and it doesn't have anything to do with how much the body rolls during the turn. No?

[This message has been edited by nsxtasy (edited 17 September 2002).]
 
I like physics. I believe that with stiffer swaybars, less weight is transferred, but not for the reasons most people might think. Nsxtacy, your assumption is almost correct.
It would be correct if the center of gravity didn't move. But as your car rolls, because of the way a spring works (force as distance squared), when the body rolls the inside lifts more than the outside drops, so the increase in the z direction of your center of gravity as a result of body roll increases the weight transfer.

Now to dispute another statement. Someone wrote that as the weight increases the coefficent of friction decreases. This is pure hubbabaloo. Your tires static coefficent of friction is a constant (more or less) and is multiplied by the downward force and the area of contact to determine how much frictional force you have. The transfer of weight may decrease your cars overall frictional force, but it is not a result of any coefficent changing.

Fritz
 
Stiffer sway bar induce lateral load transfer. It basically transfer loads from inside wheels to the outside wheels at the same end of the car, in the corner. Sway bars are mounted on the chassis, with the end link to the control arm or shocks. When the car turn, the chassis roll, and the sway bar linked to the inside wheels lifted the inside wheel (reduce the load) and transfer the load to the outside wheel.

To illustrate better, grab a ruler, and hold the ruler with your right and left fingers where sway bars are usually mounted on the chassis. Let the ends of the ruler hang free. Like this,

-----x---------------x-----

x mark where you hold the ruler.

For argument sake, we will take the case of a car turning right. Move your finger as if you are taking a right turn. Remember, right turn means, the left side is lower than the right side. You can see that the right end of the ruler lift, thus lifting the inside wheel. This reduce the capacity of the tire, resulting less total cornering capacity that can be generated by 2 wheels without a sway bar, of course keep in mind we are talking independent suspension.

I don't think sway bars are completely unnecessary. In fact they are necessary to limit body roll, and as quick adjustment to the basic oversteer/understeer balance of the car. I just like to minimize their use.

In the cas of my suspension setup, I totally blame the spring rate that contributed to my oversteer characteristics. I'm taking the rear bars off because it is the cheapest way to do, doesn't cost me anything to try. Still don't work, so I'm gonna have to spend the money to buy different spring rate, and possibly put the rear sway bar back on. I would not know this until I tested them

To quote Carroll Smith, in Engineer to Win.

"The basic division of duty between springs and antiroll bars hsa always been that the suspension spring determine the vehicles' ride rate and basic roll resistance while the antiroll bars add their torsional resistance to the roll resistance of the spring to determine the total roll of the vehicle. What many people don't appreciate is that, within reason, the suspension spring and the antiroll bars are interchangeable so far as roll resistance is concerned. We can reduce the roll resistance of an anti sway bar by x pounds per degree of roll without affecting the balance of the chassis due to roll couple distribution. So long as we add the same x pounds of resistance per degree by increasing the spring rate at the end of the car appropriate amount.
Obviously there is a tradeoff here, and it will be different for each car...."




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</A>
Join us Nov 24!
 
Originally posted by nsx4fun:
Now to dispute another statement. Someone wrote that as the weight increases the coefficent of friction decreases. This is pure hubbabaloo.
Click to expand...

I agree that it doesn't sound right. I have no concrete evidence of how the Cf of the tire changes in relative to load. I have to go by Tune To Win, by Carroll Smith, on page 17. He actually had first hand experience, and until he is proven wrong, I'll take his word.

Cf on material due varies, but mostly it is affected by temperature. For instance your brake pads don't have the same Cf value for the whole range of temperature.


Your tires static coefficent of friction is a constant (more or less) and is multiplied by the downward force and the area of contact to determine how much frictional force you have.
Click to expand...


Formula for Friction is very simple:

Friction = Normal(N) * Coefficent of Friction (Cf)

Looking at the formula, we can safely conclude that contact area has no bearing whatsoever with the total friction. Contact area, however, help wear rate. Bigger contact area means the friction force are distributed to wider contact patch, thus reducing the wear rate.


The transfer of weight may decrease your cars overall frictional force, but it is not a result of any coefficent changing.
Click to expand...

I agree. The change of the Cf on the tire is very subtle, that it is insignificant.



[This message has been edited by Andrie Hartanto (edited 17 September 2002).]
 
Andrie, I think you have it backwards as to where the load is transferred. The increase loading on the outside springs during body roll transfers some of that load through the torsion bar to the inside springs. Therefore less roll as the outside springs don't compress as much and the inside springs don't uncompress as much. In other words, the inside springs take some of the load off of the outside springs because the torsion bar transfers the load.
But loading on the springs as a result of the torsion bar is not the same as weight transfer. The weight transfer will be close to the same. You are correct, that a stiffer spring rate will also reduce body roll with out anti-sway torsion bars.
 
Fritz,

I don't think I got it backwards.

Let's go back to the drawing of the ruler. We agree that if you push the right end of the ruler will result the left end of the ruler lifting. Thus reducing the load on the inside wheel.

Now imagine it is an antiroll bar, and it has spring attached onto the ends of the bar. When you push the right end of the bar up, you are pushing against the spring at the same time, this is the force acting on the wheel/tire. Now, take a look at the left end, where the antiroll bar is pushing the spring up. The left spring is now try to push the antiroll bar down. Which resulted in transferring the load to right wheel. Thus increasing the load of the right wheel.

[This message has been edited by Andrie Hartanto (edited 18 September 2002).]
 
From what I'm reading here I get the following understanding.
Sway-bars (or stiffer springs) will reduce body roll. Doing that, the weight transfer to the outside wheel will be less. Stiffer sway-bars here will have the same effect as stiffer springs. The difference is that stiffer springs will also have an effect going straight and swaybars will not (to a degree that is, because they make the independent suspension a little less independent).

NSX4FUN states:
"..as your car rolls, because of the way a spring works (force as distance squared), when the body rolls the inside lifts more than the outside drops, so the increase in the z direction of your center of gravity as a result of body roll increases the weight transfer."

In other words, there is an upward force involved. This means, in effect, that going into the corner the car will put less total weight on the ground and the total grip on the road will therefore be reduced (this is a correct deduction or not (anybody).
To be more precise, the amount of grip that the inside tire looses is greater than the extra grip the outside wheel will have have because of the greater weight.

If all the above is correct, stiffer springs/swaybars have the effect of reducing the upward forces in a corner, therefore minimizing the loss of weight (or load) on the tires and therefore maintaining maxium tire grip. Because of this, sway-bars and/or stiffer springs will increase your maximum cornering speed cq. increase cornering grip.

Another, more general, deduction would be that in a corner a car has less grip because of the creation of an upward force.
 
The disadvantage of anti rollbar is they tie the independent suspension together. Thus a force acting on one corner will effect the other corner at the same end.

It is all about compromise. For suspension with relatively soft springs, you want to run a pretty good size anti rollbar. Just keep in mind that bigger don't always mean better.

If you really want to improve the handling, nothing beats a great tire.
 
Originally posted by MvM:
Sway-bars (or stiffer springs) will reduce body roll. Doing that, the weight transfer to the outside wheel will be less.
Click to expand...

Basically not true. Weight transfer is a function of the speed of the car, the radius of the turn, and the height of the car's center of gravity. Weight transfer is NOT caused by body roll itself. Weight transfers to the outside tires regardless of whether the body is rolling or not. This whole notion that weight fails to transfer because one side of the body is rising and the springs are "lifting up" the weight is quite simply not true.

The only reason that there is a difference - a slight difference - in the amount of weight transfer is, as nsx4fun rightly points out, due to a slight change in the height of the center of gravity as the body rolls. NOT because the springs "lift up" the weight of the body. The fact that the body rises on one side more than the other is a reflection of the weight transfer, not a cause of the weight transfer.

[This message has been edited by nsxtasy (edited 18 September 2002).]
 
If you read my first reply, notice I never uses the term weight transfer, rather lateral load transfer.

The weight transfer will be insignificant in change due to roll bar. However, the load on each tire is greatly affected by the sway bars.

[This message has been edited by Andrie Hartanto (edited 18 September 2002).]
 
NSXtasy/Andrie,

I will make some statements and its up to you (or other guys/girls of course) to correct me if I'm wrong.

1) When a car is going straight there is only the downward force of the car's mass on the tires (neglecting wind-forces etc. for the moment). (True/Not True?)

2) The car has tires on each corner. So the downward gravitational force (mass of the car) is spread out over these tires (in static situation). By definition, if an object has a constant speed no forces are applied (talking horizontally here). Assuming this constant speed going in a straight line the mass distribution over the tires will not change. (True/Not True?)

3) When cornering a new and horizontal (lateral) force will begin to apply, the rotational force wanting to car to continue in its original direction (straight). I'm sorry if I don't know the correct English term. (True/Not True?)

4) By definition, this lateral force acts upon the cars centre of gravity. (True/Not True?)

5) Since the centre of gravity is situated above and between the tires/wheels an overturning moment will be created. (if we would be a on a bike we would fall over).
(True/Not True?).

6) This overturning moment manifest itself as a force on the outside wheel. This force will push the suspension downwards, lowering that side of the car. This is what most of us call the weight transfer. (True/Not True?)

7) Since the car is not a flexible unit it will turn around its COG. So, when one side is going down, the other will go up. Because of this, the downward force on the outside wheel results in an upward force on the inside wheel. (True/Not True?).

8) Following 7, the outside wheel has more grip and the inside wheel will have less grip. (True/Not True?)

9) Connecting the outside wheel to the inside wheel in some way (swaybar) the force applied to one side will be applied on the other side as well. Since the total amount of force remains the same the force is divided (but not in equal measures) over both the outside and inside wheel. (True/Not True?)

10) The above will result in less bodyroll since the outside will be less depressed and the inside less lifted. (at least that sounds obvious to me). (True/Not True?)

My remaining is still:
If swaybars reduce the downward force on the outside and increase the load on the inside wheel will this result in better roadholding, cq. higher possible cornering speeds. I think, here is were tire-talk gets into the equasion with friction coefficients, tire contact patches, suspension effect etc. etc.
 
Originally posted by MvM:
NSXtasy/Andrie,

I will make some statements and its up to you (or other guys/girls of course) to correct me if I'm wrong.

1) When a car is going straight there is only the downward force of the car's mass on the tires (neglecting wind-forces etc. for the moment). (True/Not True?)

2) The car has tires on each corner. So the downward gravitational force (mass of the car) is spread out over these tires (in static situation). By definition, if an object has a constant speed no forces are applied (talking horizontally here). Assuming this constant speed going in a straight line the mass distribution over the tires will not change. (True/Not True?)

3) When cornering a new and horizontal (lateral) force will begin to apply, the rotational force wanting to car to continue in its original direction (straight). I'm sorry if I don't know the correct English term. (True/Not True?)

4) By definition, this lateral force acts upon the cars centre of gravity. (True/Not True?)


5) Since the centre of gravity is situated above and between the tires/wheels an overturning moment will be created. (if we would be a on a bike we would fall over).
(True/Not True?).

6) This overturning moment manifest itself as a force on the outside wheel. This force will push the suspension downwards, lowering that side of the car. This is what most of us call the weight transfer. (True/Not True?)


7) Since the car is not a flexible unit it will turn around its COG. So, when one side is going down, the other will go up. Because of this, the downward force on the outside wheel results in an upward force on the inside wheel. (True/Not True?).

8) Following 7, the outside wheel has more grip and the inside wheel will have less grip. (True/Not True?)
This will be 100% true if the car is a rigid body and don't have suspension. The independent suspension have the advantage, that when you take a corner, the spring on the inside wheel will push the inside tire down to maintain contact with the road. Ofcourse there is limitation to only the full droop range.


9) Connecting the outside wheel to the inside wheel in some way (swaybar) the force applied to one side will be applied on the other side as well. Since the total amount of force remains the same the force is divided (but not in equal measures) over both the outside and inside wheel. (True/Not True?)

10) The above will result in less bodyroll since the outside will be less depressed and the inside less lifted. (at least that sounds obvious to me). (True/Not True?)
Click to expand...

It will result in less body roll, because the anti roll bar, tie both suspension to the chassis. If you just take one end of the bars and draw a Free Body Diagram, it might come clearer.



My remaining is still:
If swaybars reduce the downward force on the outside and increase the load on the inside wheel will this result in better roadholding, cq. higher possible cornering speeds. I think, here is were tire-talk gets into the equasion with friction coefficients, tire contact patches, suspension effect etc. etc.
Click to expand...

The anti rollbar will in fact reduce the roll and can mean better handling. There is a trade off, that it also increase the load on the outside tires, reduce the load on the inside tires. Thus the total cornering capacity of both tires are reduced.

To answer your question, the anti rollbar will help you to certain extent. Going too stiff can be as bad as going to soft. How stiff is right? You don't know until you try them.

Disclaimer:
By No means I am an expert in suspension. I have engineering background and love reading suspension books. And I also stayed at Holliday Inn
biggrin.gif
Click to expand...
Click to expand...
 
Originally posted by MvM:
1) When a car is going straight there is only the downward force of the car's mass on the tires (neglecting wind-forces etc. for the moment). (True/Not True?)
Click to expand...

True.

Originally posted by MvM:
2) The car has tires on each corner. So the downward gravitational force (mass of the car) is spread out over these tires (in static situation). By definition, if an object has a constant speed no forces are applied (talking horizontally here). Assuming this constant speed going in a straight line the mass distribution over the tires will not change. (True/Not True?)
Click to expand...

True.

Originally posted by MvM:
3) When cornering a new and horizontal (lateral) force will begin to apply, the rotational force wanting to car to continue in its original direction (straight). I'm sorry if I don't know the correct English term. (True/Not True?)
Click to expand...

True. The English term is "centrifugal force".

Originally posted by MvM:
4) By definition, this lateral force acts upon the cars centre of gravity. (True/Not True?)
Click to expand...

True.

Originally posted by MvM:
5) Since the centre of gravity is situated above and between the tires/wheels an overturning moment will be created. (if we would be a on a bike we would fall over).
(True/Not True?).
Click to expand...

True.

Originally posted by MvM:
6) This overturning moment manifest itself as a force on the outside wheel. This force will push the suspension downwards, lowering that side of the car. This is what most of us call the weight transfer. (True/Not True?)
Click to expand...

True.

Originally posted by MvM:
7) Since the car is not a flexible unit it will turn around its COG. So, when one side is going down, the other will go up. Because of this, the downward force on the outside wheel results in an upward force on the inside wheel. (True/Not True?).
Click to expand...

Yes, there is an upward force on the inside wheel, which is a reflection of the greater weight placed on the outside wheel. Gravity is still acting on the inside wheel, but there is less weight there than before. (On some cars, when cornering fast, they can even lift one or both inside wheels off the ground, so that there is no weight on them at all.)

Originally posted by MvM:
8) Following 7, the outside wheel has more grip and the inside wheel will have less grip. (True/Not True?)
Click to expand...

True, but "grip" is a misleading term. The outside wheel has more grip because it has more weight.

Originally posted by MvM:
9) Connecting the outside wheel to the inside wheel in some way (swaybar) the force applied to one side will be applied on the other side as well.
Click to expand...

I don't understand this statement. Which force are you talking about - the downward force of gravity, or the lateral weight transfer force, or the movement around the COG?
 
For your consideration:

Without addressing the various speculations on the reasons why anti-roll bars have the effects that they do, it is apparently an accepted claim that a relatively stiffer bar on the front increases understeer. In and of itself, this says that a stiffer bar does reduce traction.

This is consistent with one particularly clear effect of anti-roll bars. The bars act to increase spring "stiffness" on the outside wheel by compressing the spring on the inside wheel at the same time. Thus both springs are acting while under a load. Since a displaced spring (either compressed or stretched) requires a greater force to further displace the spring than an uncompressed spring, the net effect is similar to temporarily having much stiffer springs. The force derived from effective weight acting on the inside wheel and that acting on the outside wheel is independent of the spring rate (stiffness), assuming that there is little change in roll and hence a relatively constant center of mass; i.e., under a given lateral acceleration from turning, the different loads on the inside and the outside wheel remains the same whether you have soft springs, stiff springs, an anti-roll bar or not. This assumes that there is the same tire contact patch with each spring/anti-roll bar configuration, ... hence the same lateral acceleration. The constancy of load on the wheels is experienced because the load is strictly determined by the torsional effect created by the elevated center of mass and the magnitude of the lateral acceleration. The anti-roll bar does not change the load on wheels at all, ... it just changes the effective load on the springs.

The reason that the stiffer bar has the effect on traction that it does is threefold. First and foremost, effectively stiffer springs impart more upper force to the chassis when the vehicle encounters small undulations in the road surface, thereby lifting the car, and reducing the load on tires, and hence the friction that they can generate. Thus the car is free to slip sideways more than with a car that is more softly sprung. The second reason for a change in traction would be a change in the orientation of the tire to the road because of reduced body roll in the event that body roll is changed. Depending on suspension geometry, this can be good or bad. The third reason why traction could change would be a lowering of the center of gravity when springs on both the inside and outside wheels are compressed by the load on the outside wheel. This would reduce the load on the outside wheel since the torsion on the chassis is reduced by having shortened the moment arm length which equals the height of the center of mass above the ground. I would think this effect would be small, but perhaps not..

Might be off with some of this, but this is consistent with the physics in play during corning. The effective stiffening of the springs is clear and the consequent effect seems pretty clear to me. The different downward forces acting on the wheels are also a clear effect of the torsional effect of the elevated center of mass and the lateral acceleration.

anvil



[This message has been edited by anvil (edited 18 September 2002).]
 
Without going into great detail, this is the readers digest on anti-sway bars (yes I know it disagrees with most of the above posts):

1. The weight transfer of any vehicle is only governed by lateral acceleration, CG height, and track width. Go-carts without movable suspensions still transfer weight. Using body roll by itself to guess at weight transfer is not a good idea.

2. Therefore, without a change in CG height there would be no difference in weight transfer, but stiffer bars reduce body roll by pushing up on the sprung-mass chassis ever so slightly actually increasing the CG height. Yes, beyond popular belief, stiffer bars actually increase lateral weight transfer. If you don't believe this, try disconnecting your anti-sway bars from the chassis and see if they work.

3. Tire coefficient of friction is a funtion of many factors. The two largest for this discussion are loaded weight and dynamic camber angle. The lower the weight (per tire), the more favorable coefficient of friction and therefore corning ability (on a side note, this is the sole reason lighter cars corner better than heavier cars). Tires will also achieve an optimal Cf at one particular dynamic camber angle.

The bottom line is:

Con: Due to the tire friction being better when the weight transfer is reduced, stiffer sway bars will reduce cornering ability.

Pro: Because stiffer bars hold the suspension at more constant dynamic camber angles, they will increase cornering ability and generally reduce tire wear.

Pro: Because stiffer bars reduce body roll, they improve driver confidence.

4. IMO, stiffer bars on a stock sprung NSX is about the best mod you could perform despite the above negative factors.

Bob
 
1badnsx, I agree with most of what you say, except item 2. How do anti-sway bars raise the CG? I think they lower it. Without antisway, say during more cornering, i transfer 500lbs of weight from the inside spring to the outside spring. Because of the nature of springs and that flat they are all loaded, adding 500 lbs to the outside spring will compress it less than the expansion of the inside spring losing 500 lbs of force. Net effect, CG rises because the inside lifts more than the outside sinks. Now we add our sway bars. Through the torsional transfer, some of the 500lbs of transfer to the wheel is transferred back to the inside spring. so the Torsion bar may take 300 lb's of additional load and re-direct it to the inside spring, less compression occurs on the outside spring and substantially less expansion will occur on the inside spring. Net effect, lower CG with sway bars.
 
Originally posted by nsx4fun:
1badnsx, I agree with most of what you say, except item 2. How do anti-sway bars raise the CG?
Click to expand...

nsx4fun, It would be hard for me to prove it to you on this site. You really need to do the suspension loading calculations to prove it, but I will try to explain.

The anti-sway bars have four attachment points. The bar operates during a turn by pushing up on the outside half of the sprung chassis. This prevents the chassis from rolling as much as it would without a bar. This net force requires the bar's outside attachment point on the control arm to push down, therefore more weight transfer to the outside wheel. That is where the force comes from, but it is really due to the slight increase in CG height caused by the net up force on the sprung chassis.

If you are still uncertain, either do the suspension force calculations yourself (with and without a bar) or look in most racing books and see what they say about the negative effects of anti-sway bars.

Due to the stock NSX having too much body roll and the negative effects of dynamic camber changes, I still think Dali anti-sway bars are the single best mod that can be done to the stock sprung NSX.

Bob
 
Bob,

While I agree with your original assertion that the weight transfer is strictly determined by the height of the center of mass, I also agree with nsx4fun's analysis that in the absence of roll prevention by an anti-roll bar, the center of mass will lift. After all, what happens when a car actually rolls over? The center of mass rises unquestionably. This is the extreme case, but it results from a steady increase in the height of the center of mass as body roll increases.

While an anti-roll bar does effectively increase the outside spring stiffness and hence lift the outside of the chassis, it also compresses the inside spring (also increasing spring stiffness on that side of the vehicle), thereby lowering the inside of the chassis. The net effect is a very small change in center of mass height compared to a vehicle without the roll damping effects of an anti-roll bar. The more or less constant height of the center of mass improves stability by reducing the tendency for a shift in load as the center of mass rises.

The effect of decreasing extreme body roll is clearly a plus. However, the necessity to increase "stiffness" of the springs (since all are heavily loaded during cornering with a stiff anti-roll bar) reduces the compliance of the suspension to road surface variation, and hence reduces the ability to maintain optimal adhesion. This is a net loss in the ability of the vehicle to maintain traction.

Compared to a car under no lateral load whatsoever, however, a car with anti-roll bars under a lateral load would experience a slight increase in the height of the center of mass since the outside spring is more compressed than the inside spring since the anti-roll permits some flex and does not force the inside spring to be compressed as much as the outside spring. In other words, the anti-roll bar permits some body roll and, as noted above, roll lifts the center of mass.

In the case of a perfectly stiff anti-roll bar, by contrast, both springs would act in union. Then the fact that the total downward force exerted by gravity has not changed would mean the springs remain compressed just as when no lateral load is present. Thus the center of mass has not changed. However the suspension compliance is low and the cars slips sideways fairly easily at every slight bump in the road surface.

No calculations, but I think this means we are generally agreeing on the effect of roll on center of mass, and the effect of heightened center of mass on load transfer and the overall benefit of anti-roll bars. The effect of stiffened springs under cornering loads is one thing that has not been agreed upon, I believe.

anvil
 

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Optimal size tires for 17X8 and 18x10 wheels?
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