Running a larger front bar.

[Martini Focus]

I have a quick question about the benefits of running a bigger front sway bar with an open diff. Now bear with me as I'm still new to this. When cornering the outside tire is going to loose it's contact patch to the point that only the inside edge will be making contact. Isn't a bigger front bar going to exaggerate that by reducing the contact patch earlier as the loads transfer to the outer tire? Conversely couldn't I create the similar effect of a front bar by cranking up the stiffness of my front shocks, without having the affect of possibly reducing the contact patch of my tires when turning.

I may be way off on this but I figured you guys could help me clear this up.

[GR8 Ride]

A couple of notes on this. One, your shocks should (in theory) only apply when your spring is in motion, not when it's loaded up but static in movement. This isn't an absolute, as your shocks are part of what determine the initial turn-in on your car (all other things being equal).

The idea behind a larger front sway bar is to transfer load back from the outside tire to relatively unloaded inside tire. Depending upon how the car is setup (geometry-wise), this stiffening of the front bar can cause understeer (largely driver dependent).

This is only the start to it, as suspension tuning is almost as much black-art, as it is science.


Pat

[Logan]

We need someone to host a "suspension tuning for idiots" class.
I'd be the first one to sign up.

[Martini Focus]

Ok so let me go through this again and I understand it's pretty basic but I guess that's where I need to start.

Going around a right hand corner.
As the car enters the corner and the loads up on the left front tire the sway bar will force the load back upon the unloading right front tire? Am I getting this??

I know so little about this stuff it's scary. Is there a suspension for dummies book out here, I've got a flight to cali next week and I need something good to read.

[Marsh]

Originally posted by GR8 Ride
A couple of notes on this. One, your shocks should (in theory) only apply when your spring is in motion, not when it's loaded up but static in movement. This isn't an absolute, as your shocks are part of what determine the initial turn-in on your car (all other things being equal).

The idea behind a larger front sway bar is to transfer load back from the outside tire to relatively unloaded inside tire. Depending upon how the car is setup (geometry-wise), this stiffening of the front bar can cause understeer (largely driver dependent).

This is only the start to it, as suspension tuning is almost as much black-art, as it is science.


Pat


??? huh:confused: The sway bar always transfers wheel load from the inside to the outside, not the other way around. Adding a bar at either end will reduce roll by increasing weight transfer to the outside tire. The more weight transfer you get, the flatter the car stays, but the less total grip you have. Plus you will get more inside wheels spin, since you've decreased the load on that tire. Suspension tuning isn't all that much black art. The black art is in the tires, only because manufactures never want to tell you the tire data you need to make accurate suspension calcualtions.

[Logan]

Originally posted by Marsh
because manufactures never want to tell you the tire data you need to make accurate suspension calcualtions.
Why calculate when it's so much fun to guess?

[Martini Focus]

So I was correct in what I thought would happen in my first post??

[haniforama]

Originally posted by Martini Focus
When cornering the outside tire is going to loose it's contact patch to the point that only the inside edge will be making contact.

Change outside tire to inside tire and it's correct.

Isn't a bigger front bar going to exaggerate that by reducing the contact patch earlier as the loads transfer to the outer tire?

Yes this is true.

Conversely couldn't I create the similar effect of a front bar by cranking up the stiffness of my front shocks, without having the affect of possibly reducing the contact patch of my tires when turning.

Shock effects only occur during transient motions (ie when the suspension is moving up or down). Once the car has taken a "set", you rely on the spring rates to dictate the roll stiffness.

IMO, if you want reduce inside wheel spin on a FWD car, you either need to REDUCE the front roll stiffness or INCREASE the rear roll stiffness. I would opt for the latter if that option is viable.

Hanif

[Marsh]

Originally posted by haniforama

IMO, if you want reduce inside wheel spin on a FWD car, you either need to REDUCE the front roll stiffness or INCREASE the rear roll stiffness. I would opt for the latter if that option is viable.

Hanif

Agreed, most whole heatedly.

[Martini Focus]

Originally posted by haniforama
IMO, if you want reduce inside wheel spin on a FWD car, you either need to REDUCE the front roll stiffness or INCREASE the rear roll stiffness. I would opt for the latter if that option is viable.

Hanif

Ahh ok I get it, that's why I have seen people playing around with disconnecting their front sway bar. Adding a rear bar to my car is very easy all of about 5mins work. I'm looking into getting an adjustable sway bar made but I'm stuck on how stiff to make it. It costs as much to have a custom rear bar made as it does to get a 24mm front and 26mm rear I wanted to be sure which would work best in my situation.

I guess this question would be hard to answer but is there a recommended range for a adjustable sway bar? Aftermarket bars are available in the following range.
Stock 20mm
SVT 21mm
Progressive 22mm
Eibach 25mm
H&R 26mm

Would I be better just getting one of the rear bars first seeing how that works and then moving on to an adjustable bar?

Thanks for the help guys.:)

[Carguy]

My RSX currently has a severe inside wheel spin problem. Since I changed my stock springs I’ve noticed that wheel spin occurs effortlessly in wet conditions during mild cornering maneuvers. I recently installed a set of Tein S-Tech progressive springs and I’m still running on stock shocks. I was thinking of increasing the rear diameter of the swaybar to deal with the problem. Anyway, I'm wondering if there is a rule of thumb for swaybar diameter selection?

Thanks.

[Logan]

This is what I think about rear bar sizes, and I am by no means a suspension engineer:
You can't assume a 26mm bar will be better just because it's 26mm, you have to take into account the size of the stock bar first.
A stiffer bar will increase oversteer (reduce understeer), but too stiff will make the car dangerous at high speeds.
For something like solo II, where you typically bring your focus or corolla on a trailer, you could get away some crazy suspension settings because you aren't worried about driving a death-trap on the highway to or from the event.

Intersting to note is the stock focus rear bar is 20mm, while my mazdaspeed protege with it's funky cool suspension has a stock 20mm rear bar, and this is an upgraded bar by Racing Beat.
I think the stock protege rear bar is around 16mm.
The bar used on Speed World Challenge proteges is around 22mm depending on what team you ask.
So I think 26mm is too big for MY car.

I don't think you can apply a rule of thumb to sway bars when you are talking about different cars.
You need to assess what your car does, what you want it to do, and experiment until you get something you like.

EDIT: MY COMMENTS ARE ABOUT REAR BARS

[gatherer]

Originally posted by Logan
We need someone to host a "suspension tuning for idiots" class.
I'd be the first one to sign up.

yeah I'd sign up...

how about someone write a "Suspension Tuning for Solo 2 for Dummies" book..... it would be a best seller

[Martini Focus]

I was thinking along the same lines as you and am worried about putting too large a bar on the car and having to do an emergency lane change and causing an accident rather than avoiding one.

I only ever brought my focus to events on the trailer because either the distance warranted it, to prevent having to swap tires twice in one weekend, ya I'm lazy, or to avoid the police. I do drive my focus on the street but whenever I come near the GTA I get hassled by the police. I ended up missing two events this past summer because I got stopped, harassed and inspected.

Back on topic though I was considering an Adjustable bar that would range from around 22mm to 26mm at the top end.

[Logan]

Well I have an adjustable 21.5mm bar, not much bigger than my stock bar but has some room to play in it.
I only used it once this past season due to other reasons, so I really can't comment yet on how much of a difference it makes.
It's off the car for the winter.

[ice/solo racer]

With the open diff the last thing would be to increase the front bar rate,increasing the rear bar will help with some weight transfer onto the inside front.Use front springs instead to keep roll to say under 2 degrees if possible.Using a rear bar with as wide an adjustment as possible should allow tuning for both low and high speed handling.
BTW Don Alexander has a book on high performance suspension tuning-might not be as in depth as the books Marsh uses but will help understand the basics to begin down the road to solving handling issues.

[Martini Focus]

That's just what I was looking for. Marshal must love this book with a red prelude on the cover.:D

I'm going to have a look at my local chapters this weekend.

Got any other recommendations on good books to read?

[Marsh]

I've never heard of Don Alexander's book, I'll have to check it out.

I have books that tell me how to actually calculate weight transfer, camber curves, roll gradients etc. But there is no book that will tell you what those ideal numbers are. The more you learn, the more questions you have. It never gets easy.

[pete@wheelandti]

The more you learn, the more questions you have. It never gets easy.

How true. But, to be honest, what you need to do is listen to all of the opinions of people how have done it before, then try it out for yourself.

As a rule, sway bars are a very crude tuning tool. One should try to use as small a sway bar as possible, just for tuning. If it is because of rules, then that is fine. But, sway bars do a fair number of bad things, like overload outside tires, and unload inside tires (REALLY bad for open diff FWD cars). Rear sway bars are not as bad, so big ones are ok.

When it comes to size, I have never found an aftermarket sway bar that was ever big enough. The manufacturers have to deal with a US that sues lots, so they are not going to make your car diabolical.

Have you looked into rear toe adjustment? There should be someone making rear shims, so that the toe can be adjusted. This will simulate a rear bar, when it comes to eliminating understeer.

[Greg F]

Originally posted by pete@wheelandti
When it comes to size, I have never found an aftermarket sway bar that was ever big enough. The manufacturers have to deal with a US that sues lots, so they are not going to make your car diabolical.

Have you looked into rear toe adjustment? There should be someone making rear shims, so that the toe can be adjusted. This will simulate a rear bar, when it comes to eliminating understeer.

Yup, I have to agree with you there, big time. I bought what were supposed to be the best sway bars for the Talon and didn't find them to be that great at all.

They came with all the hype about how their bars will let you four-wheel drift and that unlike other manufacturers they've removed all understeer. Well Bull Spit!

It wasn't until WTZ did my alignment that my car really started handling well. I should've done that instead of the bars and gone for shocks and springs instead.

But then I took the RX-7 out for a spin the other day and quickly realized I still need to loosen up the Talon some more.

Basically I think that any car with seating for more than two people will understeer no matter what aftermarket bar you use, because it's better for them to kill only two people in an oversteering two-seater than four in a sedan.

[Marsh]

Originally posted by pete@wheelandti
As a rule, sway bars are a very crude tuning tool. One should try to use as small a sway bar as possible, just for tuning. If it is because of rules, then that is fine. But, sway bars do a fair number of bad things, like overload outside tires, and unload inside tires (REALLY bad for open diff FWD cars). Rear sway bars are not as bad, so big ones are ok.


I disagree. Anything that increases roll stiffness transfers more weight to the outside tire. That is, by definition, how you increase roll stiffness, and sway bars don't increase ride rate.

I used to think they were evil, but working on the SAE car cured me of that. Carol Smith told me that sway bars should acount for about 40% of the total roll stiffness equation, or a little more than that. I suspect this should be lower for sedans due to the taller centers of gravity, but I tend to agree with the number in general.

[pete@wheelandti]

I disagree. Anything that increases roll stiffness transfers more weight to the outside tire

I thought I said that. :(

Not to disagree with Caroll, but since I have very little experience with Formula cars, I cannot agree or disagree. I think that most production sedans already have pleny of sway bar in them, especially in the front. They need to keep the ride comfort, while controlling lean.

You have modified your own car, mainly by stiffening your springs/shocks, correct? Did you increase the sway bar stiffness by a similar amount? If not, why not?

And, I am not going to be able to talk definitively about that proportion, until you show me some numbers about how stiff a sway bar is, compared to springs, when it comes to roll stiffness. I just do not know how to compare the two, in similar values.

[ice/solo racer]

Along with chapters try checking your local performance improvments location as they do have some selections that may help.I just found the high performance ford focus handbook by cartech advertised in my performance in motion book.It's supposed to cover engine and suspension mods,most books like this don't do a decent job on the suspension chapter but it might be worth a look if you don't have it already.
For the record I like both edition's of Don Alexander's suspension tuning books,his books are what I've based my chassis tuning on for the corolla and even though I couldn't afford all the parts necassary for proper control(plus some rules issues)it sure had me on the right track very quickly instead of getting to far away from the basic set-up.I prefer to tune with springs over bars as well(except for fwd,pull the front bar and increase the rear bar)with the rwd car.
Its going to be a matter of how hard core a street car you want to live with because tuning with LINEAR rate srings(stay away from progressive for motorsports)will make the ride quality suffer as opposed to tuning with sway bars.
Also rember just going with the stiffest springs you can doesn't mean it'll be good,our lots are a little rough and I know I could've run a little softer spring a few times to keep the tires from pattering over the bumps(partly a shock issue as well).
The stiffer you make it the harder it is to feel when your approuching the cars limits,thats why on slick days its mostly the modded cars going in circles untill things dry/swept up!:o

[Marsh]

Originally posted by pete@wheelandti
I thought I said that. :(

Not to disagree with Caroll, but since I have very little experience with Formula cars, I cannot agree or disagree. I think that most production sedans already have pleny of sway bar in them, especially in the front. They need to keep the ride comfort, while controlling lean.

You have modified your own car, mainly by stiffening your springs/shocks, correct? Did you increase the sway bar stiffness by a similar amount? If not, why not?


OK I understand you saying that you think must cars have enough bar already. I thought you were leaning towards the "make it so stiff it doesn't even need stock bars" camp. I did recently up the rear bar, after putting the stiffer springs up front. The car is much better now. Just as neutral on turn in as when I had the stiffer rear springs. Puts power down much better on exit, and doesn't get nearly as squirly on bad pavement as before. If I were road racing the car then I would do both bars (significantly larger than now), but I don't think a lot roll stiffness is as good for Solo-2 (personal opinion).

Incidently my setup is now 12kg front spring, 10kg rear spring, 25mm rear bar (stock was around 19 or 20 I think), and stock front bar.

[RegaMaro]

I'm a little confused about all thats being said here.

My understanding is that a sway bars ,or antiroll bars, purpose is to limit body roll and suspension travel during cornering. It's also a great and easy tuning tool cause its alot easier to swap out a sway bar than a spring. I've always thought it works by transferring weight off the ouside wheel and placing it on the inside wheel while keeping the roll angle to a minimum. The antiroll is deflected by a load being fed in from the outside wheel and is resisted by the spring weight of the inside wheel. All in all this keeps proper roll couple distribution for maximum traction of all tires when entering or exiting a corner. Roll couple distribution is where I agree the black art of tuning exists as on most tracks not all turns are of the same degree nor have the same ideal enter and exiting speeds. Basically I think it comes down to feel and lap times instead of bar rate numbers.

[GR8 Ride]

No, (despite my earlier comments, which I typed in a state by being dyslexic, and transposed inside and outside), the sway bar transfers load to the outside tire. This is why a relatively softly sprung car will do better in the wet, as opposed to a very stiffly sprung car.

However, these are generalizations, which is why I STILL claim that suspension tuning can be a black art; two different teams of engineers can look at nearly identical cars and find different ways of tuning them, and a variety of laptimes (just look at F1, for example). Another case in point, suspension tuning is as much about tuning for the driver's preferences, as it is about technical perfection.

For what it's worth, I too, disagree with the 'Biggest is best' sway bar theory. Sway bars are easy to tune (unlike springs), but also eliminate some of the independence in the suspension. There are several people racing professionally and regionally who are running stiff rear springs, and no rear sway bar. It works quite well for smooth tracks like Mosport, but can suffer more when the tracks get rough. Again, stuff like this is why suspension tuning is a bit of a black art; ideally, your suspension should be tuned for each individual track, and for prevalent weather conditions.

Also, TOO MUCH roll resistance (front or rear) can in fact, be slower than less roll resistance. However, most drivers equate minimal body roll with traction when cornering, even if it's not accurate. This is why it's important to balance roll resistance with
driver confidence.

As to Carroll Smith, while he certainly does have some interesting insights into suspension tuning, he's only one guy, and there are plenty of differing opinions on how to tune a chassis (open wheel or closed wheel). A lot of it depends on overall geometry, track conditions, and ultimately, the driver themselves.


Pat

[Martini Focus]

Well thanks for the info everyone while I think I understand most of what everyone is saying I see a large amount of reading in my future.

I think what's left me more confused is the interaction between the sway bar and the spring, how one can almost counteract the effect of the other. Hmm maybe counteract isn't the correct word more like interfere with.

I guess after all of this it comes down to the one fundamental thing, if the driver doesn't pick the correct line or tries to carry too much speed into a corner no suspension in the world will help.


When I first saw a Pittl event last year I thought, racing around a bunch of cones in a parking lot cant be that hard, hell they don't even go that fast. Little did I know.:rolleyes: :D

[RegaMaro]

I think what's left me more confused is the interaction between the sway bar and the spring, how one can almost counteract the effect of the other. Hmm maybe counteract isn't the correct word more like interfere with.


Altho I'm still unsure about some of the swaybar theory here I can shed some light for you.

For those who believe in the use of higher swaybar rates I think they go along the thinking that you setup your spring rates to control the braking and acceleration loads and let the swaybars control the body roll. This would be one extreme end. Others go with the thinking that swaybars are just a fine tuning element and use as little as possible. There are pro's and con's to both. One big con to using larger swaybars is that you take away from the independance of each wheel. This can make a car pretty squirrely on any kind of uneven surface, especially under braking or acceleration.

[Logan]

That's right, think about Rally cars.
Most of the fast 4WD guys have no front bar.
And a tiny rear bar.

[Carguy]

This thread contains some very good insights and I admit that I too have some reading to catch up on. Having said that and before this thread fades from memory, I would like to share a description and my interpretation of the dynamics of inside front tire wheel spin as it applies to my ride. Any feedback is well appreciated. Bear in mind that my driving skills are still very much under development.

I recently installed a set of Tein S-Tech progressive springs. I’m still running stock shocks and for the price of a set of Koni or KYB adjustables, I’ll probably shell out for a good set of coilovers - since progressive springs are a racing no-no. My stock setup was simply horrible in term of body roll and overall suspension stiffness that simply cried out for improvement.

Stock Setup
Stock front spring rate: progressive 202 lb/in max (3.6 kg/mm) - estimated
Stock rear spring rate: progressive 415 lb/in max (7.4 kg/mm) - estimated
Stock front swaybar diameter: 23mm
Stock rear swaybar diameter: 19mm
Stock rubber: 205/55-16 Michelin “No”-season tires at 30 psi front and 32 psi rear

Baseline Oservations
In spirited cornering, I noticed that there was somewhat slow turn-in response with excessive body lean, leading to mild oversteer with the rear end "snapping" or "hopping" out on occasion when accelerating out of the corner. So my main goal was to reduce body roll, and I have to admit to wanting to change the SUV-like stock ride height just for appearance sake.

Modified Setup
Tein front spring rate: progressive 308 lb/in max (5.5 kg/mm)
Tein rear spring rate: progressive 492 lb/in max (8.8 kg/mm)
Other suspension components remained the same except for a wheel alignment.

The reason I chose Tein S-Tech springs was their price and relatively high max spring rate (for progressives) as well as minimal lowering of the ride height (1.7" front and 1.5" rear). After installing the springs I had an alignment done (without camber or toe in/out hardware) and all settings were within stock specifications or at their limit. The most significant changes were rear camber at -1.5 degrees, front camber at -0.75 degrees and slight front toe-out at 3.0 degrees (1.5 degrees for both wheels).

Modification Results
The result of the modifications (all else remaining equal) is significant inside wheel spin during spirited and even mildly spirited cornering maneuvers. The front outer spring seems to compress a little more then I would expect/like after braking and upon turn-in there is slightly more body roll in front than in the rear (a drawback of progressive rate springs I assume). Upon accelerating out of the corner wheel spin occurs to the point where I fell like the car is spinning on snow/ice but I’m only in wet conditions.

Interpretation of the Wheel Spin Dynamic
When I accelerate out of a corner there is a noticeable weight shift front to rear but this is felt “diagonally” when weight shifts from the inside front wheel to the outer rear wheel. This is when wheel spin occurs – just past the apex. The way I visualize it is that a left-right transfer occurs simultaneously with a front-back weight shift while the outer front suspension is compressed making the front swaybar compress the inner front suspension. This “lifts” the inner front wheel enough to cause wheel spin.

Based on my interpretation a stiffer rear swaybar would solve the problem by reducing the effect of left-right/front-rear weight shift along a diagonal axis from the outside rear wheel to the inside front wheel by reducing rear body roll. Or am I way off on this?

[WannaBeRacer]

From testing done today on the street and on street tires, disconnecting the front bar on my civic with a upgraded rear bar springs and shocks caused "softer turn in" with better exit traction. My car is open diff and at short tracks like Dunnville maybe TMP I see this added acceleration benefitting greatly. However at Calabogie where most corners are 3rd gear my car does not create enough power to spin the inside tire.

Now I need to go to the track with a proper timing setup. I also need to see of I can get some quicker turn in with shock settings.

More then anything it appears that testing and being able to quantify the results is what's really important.