s13 Sway Bar g's
s13 Sway Bar g's
Has anyone tested to see how much front and rear sway bars really help. I can tell a difference but just wondering if anyone tested it (road test with the g rating). Just wondering I have a s13 front and rear sway bars KTS coilovers 2.5" lower and rear upper a arms to fix the camber and stock wheels and tires. If that matters at all.
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AmoebAssassin
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Re: s13 Sway Bar g's (holmeS13)
Contrary to popular belief, sway bars do NOT increase maximum traction (G rating), and I will explain why.
First, a little background on tires. Tires have a property called mu, which is a coefficient that describes the relation of the amount of lateral force a tire can generate for any given vertical load on the tire (in mathematical terms, mu = lateral force / vertical force). Modern tires do not have a constant mu, but rater a mu that varies with vertical load with diminishing returns. That means, as vertical load increases, lateral load will increase, but by a decreasing amount (less than linear relationship). Therefore, for maximum grip, it is ideal not to transfer any load from the inside to outside tire (however, this creates a car that is very difficult to drive, and therefore all cars are engineered to have a certain amount of load transfer).
Okay, now onto roll bars on an S13. True, roll bars do lessen body roll and thereby create a car that is more manageable and confidence inspiring, so it is easy to mistake "feeling faster" for "being faster". However, in order to counteract the roll moment of the chassis, sway bars will increase the vertical force on the outside tire. This causes increased load transfer to the outside tire. See above -- increasing the vertical load on the outside tire and decreasing the amount of load on the inside tire actually decreases total grip due to the tire's inability to cope with the increased vertical force.
So you're probably asking yourself, "if roll bars decrease traction, why use them on any car, ever?!" The answer to that is pretty simple -- to change the oversteer/understeer characteristics of the car. Stiffening or softening the roll bar at each end of the car changes what is called TLLTD (tire lateral load transfer distribution). Yes, it's a complicated acronym, but it basically signifies how much of the total vehicle weight transfer occurs at each end of the car. Say if the front of a certain car has a 35% TLLTD, that means out of 100% of the car's total lateral load transfer, 35% of it occurs at the front of the car, and 65% of it occurs at the rear of the car.
So now that you've got a grip of TLLTD is, lets see what changing it does. Say we have a car with 50% TLLTD at the front and rear (50% TLLTD is a "balanced chassis", or one whose front and rear tires will brake away at roughly the same time, resulting in neutral to oversteer vehicle dynamics). Now lets say we stiffen the front sway bar and leave the rear unchanged. A stiffer front sway bar causes more load transfer at the front of the car, changing the car's TLLTD to say, 60%front, 40% rear (arbitrary change to prove a point). Now, since the front tires experience more load transfer than the rear tires, the front tires will tend to become saturated first, and therefore the front of the car will wash out before the rear tires -- classic understeer.
Lets say we take this 50% TLLTD car and stiffen the rear bar. Now the TLLTD is 40% Front, 60% rear (again, arbitrary to prove point). Now, the rear tires become saturated first (as they see more load transfer than the front), and will wash out before the front tires. This is classic oversteer.
Therefore, a stiffer front bar will increase understeer, and a stiffer rear bar will increase oversteer.
As for me, personally -- I think it's a good idea to only stiffen the rear bar on an S13 and keep the stock front sway bar. S13's suffer from understeer caused by the crappy camber curves that MacPhereson strut cars create. Therefore, leaving the stock front sway bar will not reduce front grip. Add a stiffer rear sway bar to increase rear TLLTD, and therefore make the car more neutral without sacrificing front grip.
With all this in mind, to answer your original question - sway bars will reduce the G rating of the car, but will result in a car that is more neutral handling and therefore easier to drive faster, and being able to drive a slower car quickly is much better than being able to drive a quicker car slowly.
Sry for the long winded response
First, a little background on tires. Tires have a property called mu, which is a coefficient that describes the relation of the amount of lateral force a tire can generate for any given vertical load on the tire (in mathematical terms, mu = lateral force / vertical force). Modern tires do not have a constant mu, but rater a mu that varies with vertical load with diminishing returns. That means, as vertical load increases, lateral load will increase, but by a decreasing amount (less than linear relationship). Therefore, for maximum grip, it is ideal not to transfer any load from the inside to outside tire (however, this creates a car that is very difficult to drive, and therefore all cars are engineered to have a certain amount of load transfer).
Okay, now onto roll bars on an S13. True, roll bars do lessen body roll and thereby create a car that is more manageable and confidence inspiring, so it is easy to mistake "feeling faster" for "being faster". However, in order to counteract the roll moment of the chassis, sway bars will increase the vertical force on the outside tire. This causes increased load transfer to the outside tire. See above -- increasing the vertical load on the outside tire and decreasing the amount of load on the inside tire actually decreases total grip due to the tire's inability to cope with the increased vertical force.
So you're probably asking yourself, "if roll bars decrease traction, why use them on any car, ever?!" The answer to that is pretty simple -- to change the oversteer/understeer characteristics of the car. Stiffening or softening the roll bar at each end of the car changes what is called TLLTD (tire lateral load transfer distribution). Yes, it's a complicated acronym, but it basically signifies how much of the total vehicle weight transfer occurs at each end of the car. Say if the front of a certain car has a 35% TLLTD, that means out of 100% of the car's total lateral load transfer, 35% of it occurs at the front of the car, and 65% of it occurs at the rear of the car.
So now that you've got a grip of TLLTD is, lets see what changing it does. Say we have a car with 50% TLLTD at the front and rear (50% TLLTD is a "balanced chassis", or one whose front and rear tires will brake away at roughly the same time, resulting in neutral to oversteer vehicle dynamics). Now lets say we stiffen the front sway bar and leave the rear unchanged. A stiffer front sway bar causes more load transfer at the front of the car, changing the car's TLLTD to say, 60%front, 40% rear (arbitrary change to prove a point). Now, since the front tires experience more load transfer than the rear tires, the front tires will tend to become saturated first, and therefore the front of the car will wash out before the rear tires -- classic understeer.
Lets say we take this 50% TLLTD car and stiffen the rear bar. Now the TLLTD is 40% Front, 60% rear (again, arbitrary to prove point). Now, the rear tires become saturated first (as they see more load transfer than the front), and will wash out before the front tires. This is classic oversteer.
Therefore, a stiffer front bar will increase understeer, and a stiffer rear bar will increase oversteer.
As for me, personally -- I think it's a good idea to only stiffen the rear bar on an S13 and keep the stock front sway bar. S13's suffer from understeer caused by the crappy camber curves that MacPhereson strut cars create. Therefore, leaving the stock front sway bar will not reduce front grip. Add a stiffer rear sway bar to increase rear TLLTD, and therefore make the car more neutral without sacrificing front grip.
With all this in mind, to answer your original question - sway bars will reduce the G rating of the car, but will result in a car that is more neutral handling and therefore easier to drive faster, and being able to drive a slower car quickly is much better than being able to drive a quicker car slowly.
Sry for the long winded response
Re: s13 Sway Bar g's (AmoebAssassin)
holy crap. you're good so good i read everything!
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Q45tech
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Re: s13 Sway Bar g's (tamdo714)
The best lowering springs and optimum balanced sway bars can improve a sporty car's handling is ~~ <3% in G numbers or lap speeds................as tires represent 90% of what is possible.
Look at tireracks suspensiom mods test results on BMWhttp://www.tirerack.com/suspen...d.jsp
Look at tireracks suspensiom mods test results on BMWhttp://www.tirerack.com/suspen...d.jsp
Amoeb:
I appreciate your attempt to use some basic physics to analyze this situation, but unfortunately it is not enough come up with anything conclusive.
Why would swaybars come oem if they are only used to tune oversteer and understeer? It makes no sense. I could see somebody making that conclusion if sways were only an aftermarket item, but the very fact that swaybars come as oem equipment on pretty much ever car from economy cars to high performance exotics points to the fact that you are underanalyzing things here.
Swaybars DO help to maximize lateral grip in most situations. I say most, because this doesn't always apply to a completely stock car.
Similar thinking goes for coilovers. They are generally accepted as a performance enhancing item, but from looking at some of the testing SCC did, we see that coilovers can actually DECREASE lateral g's on cars with low quality or all season tires. However, once the upgrade to good UHP or near R comp tires has been made, their is a definate increase in grip provided by the Coilovers. (And this increase in grip would be more than the increase seen when running good tires on stock suspesion)
Same goes for aftermarket sways. They may or may not help when installed on a stock car, but when installed on a car that already has other suspenision modifications, they WILL increase lateral grip, as long as they are close to the proper rates to work together with the rest of the suspension.
To the original poster:
The short answer is yes, aftermarket sways DO increase lateral g's. People would not be running them if their only use was to change the understeering or oversteering tendencies of the car, because these tendencies can be more easily and effectively changed by staggering tires.
However, they might not be helping if they are overly stiff in comparison to your spring rates, or if you are running crappy tires. You have to tune your suspension to work as a whole, similarly to how you would tune all aspects of a motor setup to produce the most desirable power output.
Get some wider, lightweight wheels, and some good tires (Azenis 615, Hankook RS2 or Kumho MX or better), and I guarantee that you will be seeing much better cornering grip than stock. At the moment, I would place bets on your car actually having less grip than in stock form because of your tires.
I appreciate your attempt to use some basic physics to analyze this situation, but unfortunately it is not enough come up with anything conclusive.
Why would swaybars come oem if they are only used to tune oversteer and understeer? It makes no sense. I could see somebody making that conclusion if sways were only an aftermarket item, but the very fact that swaybars come as oem equipment on pretty much ever car from economy cars to high performance exotics points to the fact that you are underanalyzing things here.
Swaybars DO help to maximize lateral grip in most situations. I say most, because this doesn't always apply to a completely stock car.
Similar thinking goes for coilovers. They are generally accepted as a performance enhancing item, but from looking at some of the testing SCC did, we see that coilovers can actually DECREASE lateral g's on cars with low quality or all season tires. However, once the upgrade to good UHP or near R comp tires has been made, their is a definate increase in grip provided by the Coilovers. (And this increase in grip would be more than the increase seen when running good tires on stock suspesion)
Same goes for aftermarket sways. They may or may not help when installed on a stock car, but when installed on a car that already has other suspenision modifications, they WILL increase lateral grip, as long as they are close to the proper rates to work together with the rest of the suspension.
To the original poster:
The short answer is yes, aftermarket sways DO increase lateral g's. People would not be running them if their only use was to change the understeering or oversteering tendencies of the car, because these tendencies can be more easily and effectively changed by staggering tires.
However, they might not be helping if they are overly stiff in comparison to your spring rates, or if you are running crappy tires. You have to tune your suspension to work as a whole, similarly to how you would tune all aspects of a motor setup to produce the most desirable power output.
Get some wider, lightweight wheels, and some good tires (Azenis 615, Hankook RS2 or Kumho MX or better), and I guarantee that you will be seeing much better cornering grip than stock. At the moment, I would place bets on your car actually having less grip than in stock form because of your tires.
Re: (naed240sx)
threadjack/Good to see you naed.Can you come here and shed some light on staggered setup?Other tire/suspension gurus are always welcome too!!!
zerothread/212092
Sorry for threadjack. BTW, this is damn good informative thread. Whiteline sway bars are definitely on my to do list.
zerothread/212092
Sorry for threadjack. BTW, this is damn good informative thread. Whiteline sway bars are definitely on my to do list.
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AmoebAssassin
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naed:
actually, I'm one year away from my B.S. in Mech Eng. at Carnegie Mellon University, and for the past two years have been heavily involved with the suspension design of open-wheel formula race cars with my school. I've read a number of books (Carrol Smith, Milliken), and I've chatted with and learned from vehicle dynamics engineers at Ford, GM, and DCX. I do believe my understanding of vehicle dynamics is a little more mature than a "basic" understanding, and I'd thank you not to patronize me.
And no, you're wrong. Any engineering student could draw a simple free body diagram and prove to you that in order to counteract the rolling action of the chassis (or the compressing action of the outboard suspension, either way you look at it), normal force on the outside tire will be increased. By increasing normal load on the outside tire and removing normal load from the inside tire, you decrease ultimate traction -- this is a physical truth and there is no way around it.
There are only two probable situations in which a sway bar would actually increase ultimate traction:
1) Reducing body roll on a car with crappy camber gain (swing arms, MacPhereson struts, etc.). Because you've reduced body roll, your suspension geometry does not deviate as much from static settings. On cars with crappy camber gains, the more body roll the car experiences, the less sufficient increases in camber become, and the contact patch exhibits a larger tendency to roll under and the car washes out. Adding sway bars prevents this effect by reducing roll. THIS is why OEM cars come with anti-roll bars, and you can bet your *** that any suspension designer worth a damn knows that sway bars reduce maximum traction.
2) On a naturally understeering car. Adding a sway bar set that increases rear TLLTD prevents understeer and allows a driver to push harder in steady state cornering, as the car is more willing to rotate and more eager to hold an inside line, resulting in increased generation of cornering G's.
Since this guy already has coilovers, he already has significantly reduced body roll. Therefore a sway bar would not increase grip by number 1. By personal experience, my car became more oversteer prone with coilovers, and therefore a sway bar would not increase grip by number 2. Hence, contrary to what you actually said, sway bars will help more on a stock car than on a car that already has reduced body roll.
And staggering tires? Are you f*cking kidding me? The same guy that says wider tires will not increase grip (which happens to be false by the way) is saying that staggering tires will tune oversteer/understeer characteristics? Gimme a break! If you say wider tires do not increase grip, then how could adjusting tire width change your car's steady state breakaway characteristics?
First of all, having a wide range of tires and a mounting machine to quickly mount/dismount tires is f*cking expensive. An adjustable anti-roll bar is cheap, as cheap as a 7 feet of steel stock and a few mandrel bends and milled holes, and is clearly the most practical method, and this is why it is used in almost every form of racing, instead of varying stagger.
Any proper suspension should start with the tire: from here, the geometry should be manipulated so that the tire is kept at its operating temperature and at it's optimal camber setting. Using tires to tune suspension is just a crappy way of making up for improper design.
To the original poster:A full set of sways will decrease your total grip. Keep your stock front bar, and try out a HICAS S13 rear sway bar. It is thicker than stock and will make your car tend to oversteer more if this is what you're looking for. If the car still understeers, investing in a thicker aftermarket rear bar is probably a good idea.
actually, I'm one year away from my B.S. in Mech Eng. at Carnegie Mellon University, and for the past two years have been heavily involved with the suspension design of open-wheel formula race cars with my school. I've read a number of books (Carrol Smith, Milliken), and I've chatted with and learned from vehicle dynamics engineers at Ford, GM, and DCX. I do believe my understanding of vehicle dynamics is a little more mature than a "basic" understanding, and I'd thank you not to patronize me.
And no, you're wrong. Any engineering student could draw a simple free body diagram and prove to you that in order to counteract the rolling action of the chassis (or the compressing action of the outboard suspension, either way you look at it), normal force on the outside tire will be increased. By increasing normal load on the outside tire and removing normal load from the inside tire, you decrease ultimate traction -- this is a physical truth and there is no way around it.
There are only two probable situations in which a sway bar would actually increase ultimate traction:
1) Reducing body roll on a car with crappy camber gain (swing arms, MacPhereson struts, etc.). Because you've reduced body roll, your suspension geometry does not deviate as much from static settings. On cars with crappy camber gains, the more body roll the car experiences, the less sufficient increases in camber become, and the contact patch exhibits a larger tendency to roll under and the car washes out. Adding sway bars prevents this effect by reducing roll. THIS is why OEM cars come with anti-roll bars, and you can bet your *** that any suspension designer worth a damn knows that sway bars reduce maximum traction.
2) On a naturally understeering car. Adding a sway bar set that increases rear TLLTD prevents understeer and allows a driver to push harder in steady state cornering, as the car is more willing to rotate and more eager to hold an inside line, resulting in increased generation of cornering G's.
Since this guy already has coilovers, he already has significantly reduced body roll. Therefore a sway bar would not increase grip by number 1. By personal experience, my car became more oversteer prone with coilovers, and therefore a sway bar would not increase grip by number 2. Hence, contrary to what you actually said, sway bars will help more on a stock car than on a car that already has reduced body roll.
And staggering tires? Are you f*cking kidding me? The same guy that says wider tires will not increase grip (which happens to be false by the way) is saying that staggering tires will tune oversteer/understeer characteristics? Gimme a break! If you say wider tires do not increase grip, then how could adjusting tire width change your car's steady state breakaway characteristics?
First of all, having a wide range of tires and a mounting machine to quickly mount/dismount tires is f*cking expensive. An adjustable anti-roll bar is cheap, as cheap as a 7 feet of steel stock and a few mandrel bends and milled holes, and is clearly the most practical method, and this is why it is used in almost every form of racing, instead of varying stagger.
Any proper suspension should start with the tire: from here, the geometry should be manipulated so that the tire is kept at its operating temperature and at it's optimal camber setting. Using tires to tune suspension is just a crappy way of making up for improper design.
To the original poster:A full set of sways will decrease your total grip. Keep your stock front bar, and try out a HICAS S13 rear sway bar. It is thicker than stock and will make your car tend to oversteer more if this is what you're looking for. If the car still understeers, investing in a thicker aftermarket rear bar is probably a good idea.
Re: (AmoebAssassin)
I'm sorry for patronizing you. I am also pursuing a BS in ME, and have been making my way through millikan's book myself.
I'm not really going to pursue this arguement from a physics or geometry standpoint. What i do know is that swaybars are a part of the design for racecars, and they aren't just there to tune oversteer. This has been proven by skidpad testing time and time again. Look at the results from the testing that tire rack did. Yes, stiffer springs helped to produce more lateral grip, but adding swaybars helped just as much.
If swaybars really don't help for anything but tuning oversteer, and end up causing you to sacrifice grip, why not scrap them in favor of using slightly different spring rates to tune it? Good coilover dampers have enough damping adjustment to be able to work well with different rates, and swapping springs is just as easy as changing the setting on a sway. It would not be difficult to order multiple different spring rates for the front and rear of the car, and find which works best.
Also, your expese arguement with the tires is pretty invalid. The reality is that these teams DO have lots of tires sitting around. Sure, it mounting and whatnot takes time, and having multiple sizes can cost more, but after finding a tire that works well, you no longer need to have very many different sizes available.
The reality is that cost is not an issue for many of these teams, and they aren't using swaybars just for convenience.
Also, you tell the OP to get a HICAS rear bar or possible an aftermarket rear bar to cause it to be more oversteer prone. Since adding a stiffer bar will decrease lateral grip, why shouldn't he simply remove his front bar? It would have the same effect as far as oversteer, and according to you he wouldn't be loosing any grip because none of his swaybar rates had increased right?
Modified by naed240sx at 3:10 PM 11/29/2006
Modified by naed240sx at 3:11 PM 11/29/2006
Modified by naed240sx at 8:14 PM 11/29/2006
I NEVER said that wider than stock tires will not increase grip. You are mistaking me for somebody else.AmoebAssassin wrote:
And staggering tires? Are you f*cking kidding me? The same guy that says wider tires will not increase grip (which happens to be false by the way) is saying that staggering tires will tune oversteer/understeer characteristics? Gimme a break! If you say wider tires do not increase grip, then how could adjusting tire width change your car's steady state breakaway characteristics?
I agree completely. I don't mean to say that you should use tires to tune suspension. I'm saying that all the suspension components of the car need to be designed with the others in mind. A lot of people look at suspension as sort of a building. They think that you can just buy all of the bricks and end up with a tall building. (****ty analogy). People think that if they buy coilovers, sways and good tires, they will instantly have a car that handles great. It's not as simple as just stacking up the parts. I'm sure you agree with this, im just stating it to let you know where i'm coming from.AmoebAssassin wrote:Any proper suspension should start with the tire: from here, the geometry should be manipulated so that the tire is kept at its operating temperature and at it's optimal camber setting. Using tires to tune suspension is just a crappy way of making up for improper design.
I'm not really going to pursue this arguement from a physics or geometry standpoint. What i do know is that swaybars are a part of the design for racecars, and they aren't just there to tune oversteer. This has been proven by skidpad testing time and time again. Look at the results from the testing that tire rack did. Yes, stiffer springs helped to produce more lateral grip, but adding swaybars helped just as much.
If swaybars really don't help for anything but tuning oversteer, and end up causing you to sacrifice grip, why not scrap them in favor of using slightly different spring rates to tune it? Good coilover dampers have enough damping adjustment to be able to work well with different rates, and swapping springs is just as easy as changing the setting on a sway. It would not be difficult to order multiple different spring rates for the front and rear of the car, and find which works best.
Also, your expese arguement with the tires is pretty invalid. The reality is that these teams DO have lots of tires sitting around. Sure, it mounting and whatnot takes time, and having multiple sizes can cost more, but after finding a tire that works well, you no longer need to have very many different sizes available.
The reality is that cost is not an issue for many of these teams, and they aren't using swaybars just for convenience.
Also, you tell the OP to get a HICAS rear bar or possible an aftermarket rear bar to cause it to be more oversteer prone. Since adding a stiffer bar will decrease lateral grip, why shouldn't he simply remove his front bar? It would have the same effect as far as oversteer, and according to you he wouldn't be loosing any grip because none of his swaybar rates had increased right?
Modified by naed240sx at 3:10 PM 11/29/2006
Modified by naed240sx at 3:11 PM 11/29/2006
Modified by naed240sx at 8:14 PM 11/29/2006
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AmoebAssassin
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Re: (naed240sx)
Sorry man, my bad.naed240sx wrote:I NEVER said that wider than stock tires will not increase grip. You are mistaking me for somebody else.
Quote »I'm not really going to pursue this arguement from a physics or geometry standpoint. What i do know is that swaybars are a part of the design for racecars, and they aren't just there to tune oversteer. This has been proven by skidpad testing time and time again. Look at the results from the testing that tire rack did. Yes, stiffer springs helped to produce more lateral grip, but adding swaybars helped just as much.[/quote]I'm assuming tire rack did testing on close to stock cars and not fully modified cars. See the two points I made above. The grip was increased because body roll was lessened in both cases (stiffer springs = less body roll and sway bars = less body roll.
In that case, the gains by maintaining contact patch geometry with respect to the ground outweighed the detriments of increased load transfer that sway bars DO create. On a purpose built race car or extensively modified street car, I can guarantee you that the total lateral grip would decrease.
Racing is not only about lateral grip, racing is about any car's ability to navigate a course in the shortest time possible, and max lateral grip is only a small part of the equation. It sometimes makes sense to sacrifice a few hundredths of a G by adding sway bars in order to create a car that is more prone to neutral steer and therefore easier to drive faster. Driver confidence is a HUGE part of racing, and you can bet that most team leaders know this! A twitchy car is very difficult to be fast and consistent in.
Quote »If sway bars really don't help for anything but tuning oversteer, and end up causing you to sacrifice grip, why not scrap them in favor of using slightly different spring rates to tune it? Good coilover dampers have enough damping adjustment to be able to work well with different rates, and swapping springs is just as easy as changing the setting on a sway. It would not be difficult to order multiple different spring rates for the front and rear of the car, and find which works best.[/quote]Spring rate tuning is a way of changing the car's transient handling (i.e. on turn-in or turn-out or on rough pavement). Varying spring rates do not change load transfer, which is determined by the vehicle's mass and roll center heights, and therefore do not change the steady state grip characteristics of the car. Spring rates are a little more tricky to determine, and depend heavily on surface condition. The point is usually to find a good balance of compliance vs. stiffness. A more compliant spring is more likely to allow the wheel to traverse road bumps without jouncing the car, increasing traction. However, a more compliant spring will transfer load slower, causing the car to feel floaty or disconnected during turn in or turn out -- this is why you have to go as stiff as possible without sacrificing rough pavement traction.
The reason stiffer springs appear to increase grip on a stock car is for the same reason sway bars appear to increase grip -- both stiff springs and sway bars increase a car's roll resistance, preserving static alignment settings, and preventing excess roll negates any loss of grip caused by ****ty camber curves in roll.
Quote »Also, your expese arguement with the tires is pretty invalid. The reality is that these teams DO have lots of tires sitting around. Sure, it mounting and whatnot takes time, and having multiple sizes can cost more, but after finding a tire that works well, you no longer need to have very many different sizes available.
The reality is that cost is not an issue for many of these teams, and they aren't using swaybars just for convenience.[/quote]Adjusting a sway bar is often quicker than swapping a set of tires on a race car (except for teams that use centerlock style wheels -- but those teams design their **** right the first time ). Even if it is not an apparently large time difference, think of how little time teams have to dial in cars on race weekend, and think of how a task like tuning a car has lots of repetition. Lots of repetition means your small time saving is multiplied enough to make it worth it.
Quote »Also, you tell the OP to get a HICAS rear bar or possible an aftermarket rear bar to cause it to be more oversteer prone. Since adding a stiffer bar will decrease lateral grip, why shouldn't he simply remove his front bar? It would have the same effect as far as oversteer, and according to you he wouldn't be loosing any grip due to a stiffer rear swaybar rate right?[/quote]Removing the front bar would cause a considerable gain in body roll, and 240sxes have crappy camber curves in front, ESPECIALLY when lowered. This would decrease your grip, outweighing the increase due to reduction of load transfer.
Re: (AmoebAssassin)
I think one thing you are overlooking is the fact that race surfaces are not perfectly smooth. As you have said, the suspension should be designed around optimizing the tires. A car with solid suspension is going to glance off these imperfections and cause very little lateral grip.
Then again, you do want to limit body roll to optimize the suspension geometry and thus the the tire's interaction with the ground. Limiting body roll can be done 2 different ways. Let's say we want to minimize body roll to X degrees. This can be done by increasing the spring rates to Y kg/mm, or increasing the spring rates to Z kg/mm (where Z<Y), and increasing the swaybar rate to T.
Since our body roll is limited to X in both cases, it is safe to say that the individual wheel rate in both cases is equivalent. The difference is the ride rate. Ride rate is higher with case 1 than with case two, which results in a car that will not adhere to imperfect surfaces as well as case 2, even though both cases have the same amount of body roll.
Cliffs: I'm claiming that your analysis is ignoring the fact that raceways are not perfectly smooth. Because we don't have a perfect situation, swaybars are the perfect compromise, and do result in increased grip, but only if matched with a proper spring, as I mentioned before.
Your thoughts on this?
Modified by naed240sx at 9:53 PM 11/29/2006
Then again, you do want to limit body roll to optimize the suspension geometry and thus the the tire's interaction with the ground. Limiting body roll can be done 2 different ways. Let's say we want to minimize body roll to X degrees. This can be done by increasing the spring rates to Y kg/mm, or increasing the spring rates to Z kg/mm (where Z<Y), and increasing the swaybar rate to T.
Since our body roll is limited to X in both cases, it is safe to say that the individual wheel rate in both cases is equivalent. The difference is the ride rate. Ride rate is higher with case 1 than with case two, which results in a car that will not adhere to imperfect surfaces as well as case 2, even though both cases have the same amount of body roll.
Cliffs: I'm claiming that your analysis is ignoring the fact that raceways are not perfectly smooth. Because we don't have a perfect situation, swaybars are the perfect compromise, and do result in increased grip, but only if matched with a proper spring, as I mentioned before.
Your thoughts on this?
Modified by naed240sx at 9:53 PM 11/29/2006
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stealthx32
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Re: (naed240sx)
My thoughts are that you need to read the last post again. Especially the part about spring rate tuning.
Or well, you wanna know what I really think? Go out and drive, and stop pounding the refresh button. It's probably broken by now.
Or well, you wanna know what I really think? Go out and drive, and stop pounding the refresh button. It's probably broken by now.
Re: (stealthx32)
Hahah and who are you?stealthx32 wrote:My thoughts are that you need to read the last post again. Especially the part about spring rate tuning.
I did read that part. I still think what he says about swaybars only applies for an ideal road.
While what he says about springs is pretty much true, I think he should be talking about effective wheel rates and ride rates and not spring rates, because that is what truly matters. Spring rate is only a portion of the puzzle.
Hahah ohh wow. You got me good there. Im a little confused about how that proves anything though?stealthx32 wrote:Or well, you wanna know what I really think? Go out and drive, and stop pounding the refresh button. It's probably broken by now.
I'm enjoying this discussion. Amoeb is a smart guy. How about staying out of it since you don't seem to have anything to contribute. mmmkay?
Modified by naed240sx at 7:50 PM 11/29/2006
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AmoebAssassin
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Re: (naed240sx)
This is true, and I mentioned it already in my last post -- but also consider how much smoother race surfaces are compared to the street driving we do every day. The magnitude and frequency of suspension events you encounter on a race course is drastically less than what you encounter on a road. Therefore, you can get away with things on a race course that you can't get away with on a street course (shorter travel, stiffer springs, more roll resistance, etc.)naed240sx wrote:I think one thing you are overlooking is the fact that race surfaces are not perfectly smooth. As you have said, the suspension should be designed around optimizing the tires. A car with solid suspension is going to glance off these imperfections and cause very little lateral grip.
Quote »Then again, you do want to limit body roll to optimize the suspension geometry and thus the the tire's interaction with the ground. Limiting body roll can be done 2 different ways. Let's say we want to minimize body roll to X degrees. This can be done by increasing the spring rates to Y kg/mm, or increasing the spring rates to Z kg/mm (where Z<Y), and increasing the swaybar rate to T.
Since our body roll is limited to X in both cases, it is safe to say that the individual wheel rate in both cases is equivalent. The difference is the ride rate. Ride rate is higher with case 1 than with case two, which results in a car that will not adhere to imperfect surfaces as well as case 2, even though both cases have the same amount of body roll.[/quote]Yes this is true, and I do prefer my cars' roll rate to be roll bar influenced as well as spring influenced, but there is a really big problem with running ultra soft springs and just jacking up your roll bar stiffness.
Think of the mechanism behind spring support. The spring is there to provide roll resistance, but there is a huge factor in springs vs. sway bars: the damper. Dampers can be added to create a car that is critically damped (suspension will make one oscillation and then stop with no overshoot) or slightly underdamped (suspension will make 1+ oscillation with a little bit of overshoot oscillation). Overdamping is bad because then your wheel will not return to the road surface quickly enough, causing the wheel to skip off the ground.
Whereas springs can be damped in order to maintain contact patch integrity, roll bars cannot (well they can, but that's more of a purpose built race-car design and not a modded street car design). Jacking up your roll bar rate and running soft springs may seem like a good idea, but then second you hit any significant road surface imperfection, your wheel will oscillate due to the undamped sway bar's vibration characteristics. At best, this will cause a car to be shaky or unstable, and at worst cause temporary wheel-lift over bumpy surfaces and sudden traction loss.
Quote »Cliffs: I'm claiming that your analysis is ignoring the fact that raceways are not perfectly smooth. Because we don't have a perfect situation, swaybars are the perfect compromise, and do result in increased grip, but only if matched with a proper spring, as I mentioned before.
Your thoughts on this?[/quote]Yes, sway bars are a good way of controlling body roll with soft springs, but they do change your TLLTD, and soft springs will cause huge dive under braking. Therefore my personal theory on the matter is that a designer should get AS CLOSE AS POSSIBLE using roll center heights, camber curves, and spring rates (using anti-dive and anti-squat geometries to combat braking dive or accelerating squat), which is possible to accomplish. After this, any small imperfections in vehicle oversteer/understeer should be remedied with the sway bars.
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EazyBreazy
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Re: (AmoebAssassin)
Thanks for the great info guys.
I've read a lot about sway bars and yes, I tot ally agree. Sway bars will allow fine tune the suspension and that's why I decided to get Whiteline swaybars that are ADJUSTABLE. Am I spending too much here? Should I get HICAS rear one and leave the front alone. BTW, I have Stance coilovers w/RUCAs now and am planning on getting adjustable tension rod, Nismo power brace, subframe bushings...etc. I'm just trying not to waste my money on somthing I don't need that much.AmoebAssassin wrote:After this, any small imperfections in vehicle oversteer/understeer should be remedied with the sway bars.
Re: (94_240sx)
Personally my whiteline rear swaybar kinda pisses me off. As mentioned in SCC, it is too wide. This means that in order to keep from missaligning the hell out of the bushings, you have to mount it with one side of it on the outside of it's endlink, and the other on the inside. The holes are also slightly in the wrong places. The endlink lines up perfect with the soft setting, but is must be flexed over to fit into the hole for the stiff setting. Why not design it so that the endlink hangs directly between the two, so that neither is much of a reach? Whiteline needs to fire whoever designed this bar. None of this really affects performance at all, it just illustrates some carelessness on whiteline's part.94_240sx wrote:Thanks for the great info guys.
I've read a lot about sway bars and yes, I tot ally agree. Sway bars will allow fine tune the suspension and that's why I decided to get Whiteline swaybars that are ADJUSTABLE. Am I spending too much here? Should I get HICAS rear one and leave the front alone. BTW, I have Stance coilovers w/RUCAs now and am planning on getting adjustable tension rod, Nismo power brace, subframe bushings...etc. I'm just trying not to waste my money on somthing I don't need that much.
I keep debating whether or not i want to get a front bar. What i did do is make my front oem bar adjustable. I had to do this, because after lowing my car quite a bit, and running SPL TC rods, the increased castor, and lowered right height ended up missaligning the front sway endlinks a lot. Determined to fix this problem, I removed the front bar, and drilled two more holes in it. Solved the missalignment problem, and resulted in a slightly stiffer oem bar.
Within this next year i will be getting new springs (7kg/mm and 5kg/mm respectively) to replace the 8/6 springs on my kts, because i am aiming for the best possible handling on the street, and i feel that 8/6 is slightly too stiff. I will of course revert back to 8/6 rates, or even higher in the future if I start doing track events more regularly. After swapping to 7/5s I might find that i want an aftermarket front bar.
Modified by naed240sx at 6:09 PM 12/1/2006
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Poor_S13_Driver
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AmoebAssassin
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Re: (naed240sx)
OMG someone who agrees...I've been planning that setup for the past couple months, but cant scrape the cash together what with all the new turbo goodies.naed240sx wrote:
Within this next year i will be getting new springs (7kg/mm and 5kg/mm respectively) to replace the 8/6 springs on my kts, because i am aiming for the best possible handling on the street, and i feel that 8/6 is slightly too stiff. I will of course revert back to 8/6 rates, or even higher in the future if I start doing track events more regularly. After swapping to 7/5s I might find that i want an aftermarket front bar. None of this really affects performance at all, it just illustrates some carelessness on whiteline's part.
Re: (AmoebAssassin)
Haha yeah man, i've been planning on 7/5s for awhile now. I think it will feel great.AmoebAssassin wrote:OMG someone who agrees...
Amoeb, what you were writing about having an optimal spring rate that limits roll without causing the car to catch air off slight bumps...this is just speculation, i dont think anyone with a 240 has the budget for this kind of testing, but from what ive read its up over 12 on these cars
you know as well as anyone that having a 15/12 setup or whatever while retaining near stock sways, although it would be your best bet, it would be horrible on a track with any slight imperfections
even though its a compromise to run lower rates and then run stiffer bars to compensate, its one youre forced into
that said, ive also been planning on getting 7/5 springs forever, in fact when i ordered my KTS i tried to only to find out you have to buy them seperate no matter what, and the $200 for the second set of springs was better spent elsewhere at the time, but eventually its something to do
with them ill be running progress sways, which are stiff enough to work well with the rates, but not too stiff (largus)
ill then be turning around and getting higher rates on different tires, probably getting different coilovers altogether once im on slicks
you know as well as anyone that having a 15/12 setup or whatever while retaining near stock sways, although it would be your best bet, it would be horrible on a track with any slight imperfections
even though its a compromise to run lower rates and then run stiffer bars to compensate, its one youre forced into
that said, ive also been planning on getting 7/5 springs forever, in fact when i ordered my KTS i tried to only to find out you have to buy them seperate no matter what, and the $200 for the second set of springs was better spent elsewhere at the time, but eventually its something to do
with them ill be running progress sways, which are stiff enough to work well with the rates, but not too stiff (largus)
ill then be turning around and getting higher rates on different tires, probably getting different coilovers altogether once im on slicks
Re: (holmeS13)
The book that me and amoeb were referencing is Race Car Vehicle Dynamics by William F. Milliken.holmeS13 wrote:I guess I need to do some more reading on this. Someone said they were reading a book and was just wondering were you would find it.
And as Nismofly said, you definately need a good engineering backround and knowledge of calculus to be able to comprehend it. That being said, its a pretty amazing and in depth book.
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sleepyRPS13
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