How sway bars work, and why people use them.

XrunnIT

Active Member
Credit given to houseofthud (http://www.houseofthud.com/cartech/swaybars.htm)


Here's how a sway bar works.

Normally, without a sway bar when the car corners the weight of the chassis
shifts toward the outside of the turn compressing the springs on that side. The
springs on the inside generally extend a little, or do nothing. Relatively to the
chassis itself, it appears that the outside suspension compresses and the inside doesn't.

A sway bar couples the suspensions on each side to each other, *AND* relative
to the chassis. If you could put the car up on a lift and actually compress
the suspension on one side by hand, then a sway bar makes the compression of one
side also try to compress the suspension on the other. Ok.. it's still not
really obvious why that's useful so I'll say the same thing a different way.

A sway bar effectively increases the spring rate on whichever side
is compressed the MOST. If the sway bar were absolutely solid with no
twist so there's a 100% coupling between each side then
an attempt to compress one spring actually becomes an attempt to
compress both springs. It doubles the spring rate. If the bar has some
twist, then it may only increase the spring rate by say 50% on whichever side
is compressed the most.

So you're driving down the road and you go over
a bump that goes across the entire lane. The sway bar
does nothing. Both sides compress normally. You go around a
corner and the chassis starts to lean and compress the outside
suspension and now it's as though you have a bigger spring
out there, so the car remains more level. That's the good part.
Here's the bad part. You hit a bump with only one side, and it
behaves the same way, as though you have a stiffer spring,
so you feel uneven bumps more. You feel it crossing anything
diagonally as well, such as coming into or out of a parking lot
or driveway curb.

That's all the simple "How does a sway bar work?" part.
The real tricky one is.. "What does a sway bar do?"
1. We know it keeps the car more level. So what? Limiting the lean of
the body is good because it means that when you take a quick set into
a turn, that the body isn't still moving sideways after the tires at their
limits. Otherwise you turn in quickly, the tires grip, then the body finally finishes
leaning, when it stops, the tires loose grip. This is especially noticable in most
cars in the slalom where you lean one way then the other and so forth.

2. It limits camber changes. The camber is the angle that the tire leans in or out at the top
relative to the chassis of the car. The camber directly impacts the angle at which the tire
cross section meets the road and thus controls lateral grip. As the suspension compresses
the camber angle generally changes relative to the chassis. With a normal Macpherson
strut that hasn't been lowered, the camber goes from positive to more negative as the
lower A arm swings out straight, and then back to positive as it swings up. That swing
up into positive camber is BAD. At that point the chassis is already leaned over so the
tire may be starting to roll onto its sidewall. Changing the camber even more positive
just just nasty. A big sway bar will prevent the body roll in the first place, and
prevent the suspension compression on the outside which causes the positive camber
change relative to the chassis.

3. Transfer lateral grip from one end of the car to the other.
This one is a real trick to understand, but racers exploit this EVERY time they go
on the track. Their spring rates are often so high, the cars so low, and their
suspension travel so little, that the whole camber and body lean problem is already
a non-issue. The car doesn't lean much with 500 lb springs. They use their bars
to change the balance of the car. Here's the simple rules first.
A big bar on the front, increases rear lateral and motive traction.
A big bar on the rear, increases front lateral and motive traction.
The applications. If the car is understeering, decrease front bar size, or increase
rear bar size. This increases front lateral grip and decreases rear lateral grip
giving the car a more neutral to oversteer feel. Reverse the process for
too much oversteer.
I mentioned motive grip. That's the neat one. Let's say your RWD car is handling ok, but
everytime you get into a corner hard and get on the gas the rear inside tire breaks loose
and spins. You can't accelerate out of the turn. You can go around the turn quite
quickly, but you can't accelerate out, and the guy with traction hooks up and
passes you halfway down the next straight because he came out of the turn going 3-4mph faster.
The reason you're losing the traction at the inside rear, is usually because the rear bar is too big.
As the rear outside suspension compresses, it's actually causing the rear inside suspension to
compress as well (because the bar couples the sides.. remember where we started), and that
decreases the weight on the rear inside tire.
First thing. Decrease size of rear bar. That decouples the sides a bit, let's the inside tire press
down on the road more and thus not spin when you're on the gas.

Here's where it gets really tricky.
If decreasing the size of the rear bar doesn't help enough the next thing you do is
increase the size of the front bar. When the outside front compresses in a corner, it
causes the inside front to compress and may actually lift that tire completely off the
ground. The car is now sitting on 3 tires and guess where the weight that was on
the inside front goes? Outside front? Some of it. The rest goes to the inside rear
where we need more grip. The total weight of the car hasn't changed. It's just been
redistributed, and a sway bar at one end, actually transfered weight to the other
end of the car. Here it is in action on a RWD car.

liftedfront.jpg



See the inside front tire off the ground. That translates into more motive grip
at the rear, and thus more acceleration, and believe me, that car rockets
out of corners.

All of this trickery applies to a FWD car too, and since the front tires share all of the
motive AND most of lateral traction (because most of the weight is in front), all the things
that happen with big bars at either end are even more extreme. A big front bar stabilizes the body
lean more but also creates a lot more understeer, and may make the inside front tire spin madly under
power in a corner. A big rear bar can't give you back much lateral grip up front, but it can
give you back some motive traction. Basically lettting you
accelerate out of the turn, even when the front end is sliding pretty badly.

Here's a big rear bar in action on a FWD car.

standard.jpg
 
How do stabilizer bars work?
Stabilizer bars are part of a car's suspension system. They are sometimes also called anti-sway bars or anti-roll bars. Their purpose in life is to try to keep the car's body from "rolling" in a sharp turn.Think about what happens to a car in a sharp turn. If you are inside the car, you know that your body gets pulled toward the outside of the turn. The same thing is happening to all the parts of the car. So the part of the car on the outside of the turn gets pushed down toward the road and the part of the car on the inside of the turn rises up. In other words, the body of the car "rolls" 10 or 20 or 30 degrees toward the outside of the turn. If you take a turn fast enough, the tires on the inside of the turn actually rise off the road and the car flips over.
Roll is bad. It tends to put more weight on the outside tires and less weigh on the inside tires, reducing traction. It also messes up steering. What you would like is for the body of the car to remain flat through a turn so that the weight stays distributed evenly on all four tires.
A stabilizer bar tries to keep the car's body flat by moving force from one side of the body to another. To picture how a stabilizer bar works, imagine a metal rod that is an inch or two (2 to 5 cm) in diameter. If your front tires are 5 feet (1.6 meters) apart, make the rod about 4 feet long. Attach the rod to the frame of the car in front of the front tires, but attach it with bushings in such a way that it can rotate. Now attach arms from the rod to the front suspension member on both sides.
When you go into a turn now, the front suspension member of the outside of the turn gets pushed upward. The arm of the sway bar gets pushed upward, and this applies torsion to the rod. The torsion them moves the arm at the other end of the rod, and this causes the suspension on the other side of the car to compress as well. The car's body tends to stay flat in the turn.
If you don't have a stabilizer bar, you tend to have a lot of trouble with body roll in a turn. If you have too much stabilizer bar, you tend to lose independence between the suspension members on both sides of the car. When one wheel hits a bump, the stabilizer bar transmits the bump to the other side of the car as well, which is not what you want. The ideal is to find a setting that reduces body roll but does not hurt the independence of the tires.
 
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XrunnIT

Active Member
The more I read the more I want a UPGRADED SWAY BAR. A bigger bar (not crazy big) will only help. :rock:

This was in your first post. :top:

If you have too much stabilizer bar, you tend to lose independence between the suspension members on both sides of the car. When one wheel hits a bump, the stabilizer bar transmits the bump to the other side of the car as well, which is not what you want. The ideal is to find a setting that reduces body roll but does not hurt the independence of the tires.

This is what the truck has right now, as designed by Toyota, which outperformed the 350z. They didn't go bigger for a reason, yet they went larger then the rest of the Tacomas for another.
 
This is why I added (big but not crazy big) I don't care what size sway bar you have if you are in a turn and hit a bump it will interfere no matter what. This is what they call give and take. For every mod that you do you give up for getting if you know what I mean. Like I said before. I have done this on 2 other trucks and the handling was superior to these XRs. But they also were not as heavy as our XRs.:driver: Think about it this way. If you are turning in a go kart and hit a bump you have to work the steering wheel to recover. But on the flat turns with no bumps you can accelerate with no problem (kind of like driving on rails) this is another reason driving skills would help and by paying attention to the road. :top:
 

CBRBob

Active Member
Many people just want to throw parts at the truck with no idea of the actual benefil(or negatives) that will be gained. Think to yourself, what will I gain or lose when I do this? If you don't really know, then you probably should NOT do it.
 

Hitman

Active Member
so in other words toyota did a great job at this? which is why we dont really need any sway bars?? :dontknow:
 

XrunnIT

Active Member
This is why I added (big but not crazy big) I don't care what size sway bar you have if you are in a turn and hit a bump it will interfere no matter what. This is what they call give and take. For every mod that you do you give up for getting if you know what I mean. Like I said before. I have done this on 2 other trucks and the handling was superior to these XRs. But they also were not as heavy as our XRs.:driver: Think about it this way. If you are turning in a go kart and hit a bump you have to work the steering wheel to recover. But on the flat turns with no bumps you can accelerate with no problem (kind of like driving on rails) this is another reason driving skills would help and by paying attention to the road. :top:

What kind of racing do you do?

so in other words toyota did a great job at this? which is why we dont really need any sway bars?? :dontknow:

They did a good job. For those that do a lot of racing, stiffer sway bars will help. Even for spirited driving though, nobody has pushed the limits of the stock sway bar? That's why I used the reference, its like putting drag slicks on a stock geo metro. Ya it could hlep, but the car can't spin the stock tires, so why do you need slicks?
 

XrunnIT

Active Member
Exactly. I agree with ya they will help. Meaning BEEFIER SWAY BARS. :top:

They will help with course/track racing... There isn't any type of street racing that pushes the limits of these trucks. And any type of street racing that does is just plain stupid. And I hope to never meet someone who tries to find the trucks handling limits by testing it out on the street, because that is how people die. :thumpdown:

I've pushed the truck to the limits and beyond in autox. I can tell you one of the handling issues is exiting a corner, the other is understeer.

Issue 1 - Exiting a corner
When exiting the corner the rear inside tire will break loose, causing a slower exit.
Cause - Rear sway bar is too big in comparison to the front.
Fix - Smaller rear sway bar or larger front sway bar.

Issue 2 - Understeer
Truck pushes too much when entering a corner and has a tendancy to understeer.
Cause - Front sway bar is too big in comparison to the rear.
Fix - Larger rear sway bar or smaller in the front.

Now if somebody or company has the time and money to road test enough setups to find one that is better then our current setup then that would be awesome. But then it would only be appropriate for a stock vehicle or a lowered one depending on the truck used for R&D.

*EDIT
On ADDCO's website (sway bar manufacturer) they describe briefly the purpose of a sway bar and what not. They state in bold letters... "BIGGER IS NOT ALWAYS BETTER"
 
Thanks Xrunnit for the full explaination. There is never a day that goes by that we stop learning. :top: Now let's get some beefier sway bars kickin off here.
 

lucke

New Member
Yes. For some it is not.
you're missing the point. sway bars are for stabilization while turning, not for traction in a strait line. there's a reason sway bar manufacturers take their time in coming up with the perfect size sway bar, too big and you create more problems than what its worth (too stiff so it rips out the subframe), but too small and it doesn't stabilize enough in the turns and you still get massive body roll.
 
you're missing the point. sway bars are for stabilization while turning, not for traction in a strait line. there's a reason sway bar manufacturers take their time in coming up with the perfect size sway bar, too big and you create more problems than what its worth (too stiff so it rips out the subframe), but too small and it doesn't stabilize enough in the turns and you still get massive body roll.
I don't think you understand that I am not missing the point. I have posted a couple of times a while back begging someone to make a bigger bar. If they build it we will buy it. And I would love to be the first. I'll bet you your moderator job that it will kick butt!! :rock:
 

lucke

New Member
I don't think you understand that I am not missing the point. I have posted a couple of times a while back begging someone to make a bigger bar. If they build it we will buy it. And I would love to be the first. I'll bet you your moderator job that it will kick butt!! :rock:
please... explain to me the benefits of a larger sway bar for your street racing or even drag racing that doesn't include any lateral movement... i'd love to hear it
 

XrunnIT

Active Member
I don't think you understand that I am not missing the point. I have posted a couple of times a while back begging someone to make a bigger bar. If they build it we will buy it. And I would love to be the first. I'll bet you your moderator job that it will kick butt!! :rock:

That's the point that your missing... Forget all about body roll, as that is only a very small part of what makes a car handle good. A larger front sway bar is going to increase the understeer (while helping the corner exiting). Now there are only a handful of guys on this site that need that, and they are the ones that are into course and track racing.

Out on the streets, its not going to help. Why? because your not going to be cornering fast enough to have the rear inside tire break loose. So your not having that problem to fix...instead your creating a new problem, and that is causing more understeer. Which could potentially cause an accident if you go into a corner too fast.
 
please... explain to me the benefits of a larger sway bar for your street racing or even drag racing that doesn't include any lateral movement... i'd love to hear it
Nah. Won't waste my time. :wink:

That's the point that your missing... Forget all about body roll, as that is only a very small part of what makes a car handle good. A larger front sway bar is going to increase the understeer (while helping the corner exiting). Now there are only a handful of guys on this site that need that, and they are the ones that are into course and track racing.

Out on the streets, its not going to help. Why? because your not going to be cornering fast enough to have the rear inside tire break loose. So your not having that problem to fix...instead your creating a new problem, and that is causing more understeer. Which could potentially cause an accident if you go into a corner too fast.
Xrunnit, I hear what your sayin and agree with ya on many points. I haul weight in the rear all day and body roll is increased with more weight. So in my case a bigger ANTI SWAY BAR would help big time. And I can fill ya'll in on any down side and the good points after installation. Will be on the phone mana with some companies. Thanks Xrunnit for helping with this.
 

TitanRattler813

Well-Known Member
I have an observation-based question for DallasCowboys here:

Usually when there's a discussion about mods in which you're involved, at some point it is mentioned how much weight you haul regularly, as if it applies to the mods involved. It's also been established that you're pretty performance oriented in your objectives. My question is, are you hauling ass while you're hauling all this stuff in your bed or are you trying to optimize your vehicle for two totally isolated scenarios (one being hauling work stuff, the other being hauling ass)?

My reason for asking is that from reading all of this sway bar info, it seems as if you're attributing your excessive body roll to the extra weight being hauled around. If you get this big beefy sway bar, you may love it when you have a large load (because it solves your problem) and hate it when you're "street racing" (provided there will be a lot of high-speed sharp turning) because it could cause you a new problem.
 
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