Anti roll bars also known as (sway bars), starting with the basics the sprung weight of your car; (sprung weight being all the weight that is supported by your springs or everything over your suspension). All sprung weight will transfer depending on what your are doing with your car, from front to rear while you are accelerating or rear to front while braking. However what we are worried about now is the transfer of weight from side to side as you turn, when a car is turned into a corner the weight of the car is transferred to the outside tires and the car leans out in an attempt to continue on a strait line. This then results in three bad things, it raises your center of gravity and throws off the balance of the car, it limits the amount of tire in contact and therefore total traction with the road surface, and it rolls the outside tire resulting in positive camber and there for no camber thrust. To limit this there are a few things we can do depending on the type of suspension your car utilizes, however for this I will keep it simple so only go over the two most common. The first thing you can do to limit the roll of a car is increase the spring rate of your springs, however this can also be detrimental because the higher the spring rate the more your car will bounce unable to absorbe bumps causing you to lose contact with the road surface and there for lose traction. Dampeners (shocks) help to control this but as a rule you want to go with is use the softest springs that you can possible get away with. So in keeping with this theory we need a way to limit the roll of the car while keeping the spring rate as low as possible, the answer to this is an anti-roll bar (sway bar).



An anti-roll bar is in fact only a torsion bar or torsion spring that is connected to both sides of your suspension. When a car corners the springs on the outside of the corner are compressed forcing the sway bar that is attached to that side of the suspension down as they compress, this force is then transferred through the bar to the other side of your suspension forcing the springs on the inside side of the corner to compress as well, the result is less body roll, a lower center of gravity, and tires that maintain negative camber resulting in camber thrust and better overall traction. All these positive factors are gained by just keeping the car level or as close to level as possible. So if I went over your head I will say it once again an anti-roll bar transfer’s car weight from the outside of the car to the inside during cornering through a torsion spring that is connected to both sides of your suspension.

Now you’re thinking, well this is great I will just get the biggest bar that I can fit on my car and not have to worry about body roll at all, but like with most things to much of a good thing just never seems to work out. The problem with installing a sway bar that is to stiff, is you have connected your suspension together and you no longer have individually moving suspension. Think of an American pickup truck with its live axels with the body supported by leaf springs, every force that impacts one side of the truck is transferred through the axel to the other side of the truck. In a work truck this isn’t going to cause you too many issues but in a performance car where traction can be life and death this is a very big deal. Remember that the only thing keeping you from crashing are the four tire patches that are in contact with the road surface and the more you can keep those tires in contact with the road the faster you are going to accelerate, slowdown, and corner. The trick in picking a good anti-roll bar is to find the best medium between keeping the car from rolling and keeping the suspension as individual as possible.



Now that you understand what a sway bar does and how it works I will go over a few facts relating to the front and rear of a car. There are two sway bars on a car one in the front and one in the rear i.e. one for each set of wheels, since we live in a three dimensional world we can’t only worry about motion in one direction we have to think about what the car is doing as a whole meaning that while a car is cornering it is also moving forward and losing speed so weight is being transferred forward as well. Now forgetting about all the other aspects of your suspension and aerodynamic system and focusing on the sway bars. As a rule regardless of weather you’re car is FWD or RWD the stiffer you make the front of your car the more it will understeer and the stiffer you make the rear the more it will oversteer, the goal of any builder is to try and make the car steer as neutral as possible. To do this you may have to add a stiffer/softer front or rear anti-roll bar, or softer/stiffer springs but remember the issue with stiffer springs.



Most performance anti-roll bar on the market are adjustable meaning that they have a stiff and a soft setting, this is nothing more then two sets of holes where you are able to connect the end links. An anti-roll bar are composed of a length of metal tubing or a metal rod and is in essence shaped like a U with two short lateral arms connected under the car by a long length. The shorter the lateral arms are the stiffer the bar will be so on adjustable bars the stiffer setting will be the hole closer to the part of the bar that connects the two sides of the suspension.

Depending on the material used in the construction and if it is a hollow or solid bar will determine the strength of the bar. For those of you that you that would like to work to find out the strength of you’re sway bar or are looking to get a new one and would like to calculate how much stiffer the new on will be, here is a calculator for you.

http://buildafastercar.com/tech/Sway-Bar-Rate-Calculator



I plan on doing more write ups for the forum on other suspension topics such as alignment dynamics, spring rate and dampeners, roll centers, slip angles, Ackermans angle, and much but please feel free to ask any questions I am more then happy to answer them.

I don't mean to take away from this particular topic, but I think it would be a good idea to write up a detailed analysis on what "handling" actually is. Seems many think this is some sort of value that can be arbitrarily increased when that's not even remotely the case.

As per the topic, I am having a difficult time understanding the logistics of transfering weight from the outside towards the inside with regards to a swaybar. My understanding is the bar provides resistance on the loaded (outside) and unloaded (inside) tires, requiring more force to roll to the same angle as before without the bar. For the unloaded tire, this reduces droop travel and can essentially result in a vehicle three-wheeling around a corner. Kind of like this:

http://www.fogville.com/%7Emgm/cars/fox.GIF

the sway bar dose provide resistance to roll from the loaded to the unloaded side, however the way it does this is the spring compressing on one side therefore twisting the bar and transferring the weight to the unloaded side of the car causing the unloaded spring to compress. It will take more force to roll the car to the same angle then it would without a sway bar but this isn't because the bar is resisting weight transfer, it is because the bar is transferring weight to the unloaded side which is not allowing the body to roll. on a car with 50/50 weight distribution I would say for sure that the rear sway is to stiff but this car in the picture may indeed have to large of a rear sway bar however it is more likely due to the weight destitution on the car. Front engine FWD cars tend to have a lot more weight in the front of the car then in the rear; they also have much stiffer front suspensions then rear which makes them pigs to understeer. To solve this many people install larger rear sway bars and smaller front bars in an attempt to stiffen the rear and soften the front or the car. However there is still the issue of weight which may be as much as 65%f and 35% rear. so lets say that when this car is standing still it's weight distribution is 300lbs left front wheel, 300lbs rfw, 100lbs lrw, and 100lbs rrw now as the car corners at speed but braking the weight of the car is moved forward and laterally so lets say the weight destitution is 500 flw, 250frw, 0rrw and 50lrw. The weight of the car is the same but is now distributed differently in relation to what the car is doing. Another aspect that will effect this is how good the tires on the car are, if he were using all season tires the back end might just slid around but with r compound tires the coefficient of traction is that it can still hold the car with only the outside tire howeve the weight is still being transferred. If this still doesn’t make sense to you please keep the questions coming I will do my best to answer them for you. About the surjection for making a write up about handling, I think it is a good idea as something basic so I think I might do that, but handling is a very in depth topic with a lot of aspects to cover. I will write something short but as I get a chance to cover more and more topics I think most people will start to get a good understanding.

thanks for you're impute!

I have the Racing Beat rear bar on my FD. Alot of guys on the klub don't like it, but I've had good luck. I need to get widefoot mounts for the stock front bar.

is it stiffer then the original? and what at you trying to make your car do?

I drove my car one time with the rear sway bar unbolted at one end (by accident)...I almost ended up in a ditch, that was unnerving

yeah it's amazing how much sway bars effect they way your car behaves.

...but this car in the picture may indeed have to large of a rear sway bar however it is more likely due to the weight destitution on the car.

Surprisingly, its a little bit of both and a lot of it is OEM with it's dog-leg characteristics. Being a VW (it is a Fox) prior to 2006, it uses a torsion beam style rear end which is designed to do two things; act semi-independant to allow independant movement of the wheels, and counteract the immense understeer (most VWs are between 60-68% forward weight bias) by acting like a large sway bar. If you're careful enough, you can get any bone-stock VW prior to 2006 to dog-leg like this.

Getting back to the topic, the reduction in roll has more to do with resistance to roll on the loaded side than transfer of weight to the unloaded side. The picture posted is a perfect example of this since according to your statement, the car really shouldn't be dog-legging like that. You're basically bumping the wheel rate without the added loss in comfort that is associated with a stiffer spring and damper, but sacrificing independant movement.

ok I can see where your coming from with this, but that would be in direct relation to your spring rate. Good I like the way the thread is going.

I have the Racing Beat rear bar on my FD. Alot of guys on the klub don't like it, but I've had good luck. I need to get widefoot mounts for the stock front bar.

My FD had a stiffer one than the Racing Beat.

As a matter of fact it was the stiffest one on the market.

Addco solid 7/8" in the rear.

Couple that with good negative camber and staggered tires and nothing to this day outhandled that beast.

Dam....... I'm missing it....

Right, and you can't have one without affecting the other in some sense.

an ultra stiff rear sway bar is not necessarily ideal for handling, there is such a thing as too stiff, especially on rough surfaces

yes that and also depending on the original layout of your car, is it stiffer in the front or stiffer in the rear, RWD cars tend to have less front of a front sway bar then rear to start with. Tho optimal rear sway will rotate your car without locking the suspension.

RWD cars tend to have less front of a front sway bar then rear to start with.

I'm going to disagree with you on this one. Seeing as how a stiffer front end is conducive towards understeer, add in the ability to rotate the car with the throttle, and I would say the majority of mass produced RWD cars in stock trim are going to have a stiffer front sway bar relative to the rear sway bar per OEM design. Having it like you said is opening up a whole can of worms for the legal department. Remember, understeer is a bit more on the safer side of things since the general public will be able to get out of that sort of slide much easier than in an oversteer situation.

well I am saying that because in a RWD car the softer your front roll bar the more power you are able to apply to the rear, normally street cars aren't setup to handle well out of the box.

well I am saying that because in a RWD car the softer your front roll bar the more power you are able to apply to the rear...

How so? Sway bars shouldn't have any affect on compression and rebound when both sides are acting in unison, figured that was the springs' job...

On cars/trucks? Good.

On snowmobiles? Bad.

How so? Sway bars shouldn't have any affect on compression and rebound when both sides are acting in unison, figured that was the springs' job...

There is always going to be more force on one side of the suspension then the other in a RWD car, this is because of the centripetal force caused by the spinning of the drive shaft. In drag racing this is countered by loading one side of the suspension usually by raising one side of the car. This is all fine and good but doesn’t work well when you incorporate corners into your suspension equation. Remember that the sway bars work together affecting the force transferred from front to rear as well as from side to side, so a larger bar in the rear will decrease rear lateral traction in doing this it limits weight transfer planting your rear wheels and enabling you to maintain the highest traction coefficient possible on both of the rear wheels.

On cars/trucks? Good.

On snowmobiles? Bad.

yes a sway bar on a snowmobile would just stick out the sides and catch trees!!!

an ultra stiff rear sway bar is not necessarily ideal for handling, there is such a thing as too stiff, especially on rough surfaces

I have the same size Addco bars on the GTO.

Helped alot, yet still allowed it to lean just enough so that I don't get hit with handling surprises at the limit......

There is always going to be more force on one side of the suspension then the other in a RWD car, this is because of the centripetal force caused by the spinning of the drive shaft. In drag racing this is countered by loading one side of the suspension usually by raising one side of the car. This is all fine and good but doesn’t work well when you incorporate corners into your suspension equation. Remember that the sway bars work together affecting the force transferred from front to rear as well as from side to side, so a larger bar in the rear will decrease rear lateral traction in doing this it limits weight transfer planting your rear wheels and enabling you to maintain the highest traction coefficient possible on both of the rear wheels.

Makes sense, except I think you're referring to torque and not centripetal force. Torque explains better why you see big block, RWD drag cars twisting frames when they launch since it's torque that is wanting to rotate the vehicle around the centerline of the drivetrain.

yeah I think your right torque, thanks!

Torque also presents a problem for FWD handling in the form of torque steer as well.

And it's a terrible movie.

Torque also presents a problem for FWD handling in the form of torque steer as well.

And it's a terrible movie.

Yes this is a result of unequal length axels as well as soft engine mounts, or flex in the sidewall of the tire. I have very little on my turboed RSX with upgraded engine mounts and a Quaife LSD installed.

never seen the movie....don't think I will bother now!

Yes this is a result of unequal length axels as well as soft engine mounts, or flex in the sidewall of the tire.

Torque steer starts to get interesting once you incorporate corners into the equation, mostly due to the steering axis' relationship to the center of the contact patch. Not something you want to be wrestling around with when exitting a corner at 100mph.