Going Big... Swaybar that is [Archive]

ConeKiller

02-18-2002, 08:11 PM

Nope, I'm talking about the front. And Thought if I could find, say a 1 3/8 inch front bar or bigger, that I might try it.

If you can get a big enough bar, you might be able to get the front end of the car a little flatter.

Imagine, say a 2 inch bar.... I don't think you'd have too much wheelspin. You would have other issues to deal with though...

Keep in mind I'm already using custom Koni Double Adj up front, and on full stiff you can't compress the suspension with your weight.

Rick

Raymund

02-18-2002, 08:13 PM

[EDIT]

hotchkis makes a 25mm hollow front bar and the TRD sportivo front sway is a 24mm solid.

autxr

02-19-2002, 06:34 AM

We are getting posts everywhere, so I'm starting a new one.

Rick is wanting to do some tuning. A big fat bar to hopefully eliminate body roll to the point where the inside front stays plants.

Or a soft bar to allow the fornt wheel to droop enough that it stays planted.

Is that a fair assessment Rick?

As for a softer bar, here is what I'm going to do (I hate secrets).

I have the drilled sway bar "mod" already. I'm going to use those 2 holes to bolt an extension on to the sway bar. This will allow me to move the endlinks out several inches from stock. This should soften the bar by about 20% just by way of the longer lever arms. Now I will have one setting stiffer than stock, stock and 2 settings softer.

Maybe I will get something made up this week to show off in Ft Myers.

Scott

CloNeGTS

02-19-2002, 08:03 AM

I was hoping someone would say that if you got a big enough front bar, so much body roll would be eliminated, the front wheel wouldn't pull up.

I can't imagine going with less than stock bar in the front. Like I said in the other post, with just the ST bar in the rear, the rear end gets all kinds of crazy when really taking the corners. I can only imagine that less bar in the front keeping the whole car flatter would make this problem worse.

CloNeGTS

02-19-2002, 08:05 AM

I'd love to hear the results of this. From my experience with just a larger rear bar, I can't believe less front bar would improve the handling situation much. Yeah, the front inside may not spin, but you'll be rolling like a old Corola hatch on stock bars.

preparedcivic

02-19-2002, 08:47 AM

Typically, a softer front bar will allow more power to be put down, as the less stiff torsion action of the lighter bar allows the inside tire to unload more and stay planted. It also effectively changes the front-rear balance and will make for less understeer and more oversteer. As assy as Celicas can be, along with how much they like to light up inside tires too, I'm of the opinion the stock bar is a good compromise for stock class autox. Softer will likely increase the tail happiness, and stiffer will keep the inside front in the air for more wheelspin. Lots of rebound in the rear shocks will accomplish the same thing, by minimizing rear to front weight transfer.

I have lots-o experience with all this while playing with the Prepared car set-up over the years. I ended up with no front bar there, but an adjustable 7/8 incher on the rear full stiff, and 500 lb springs all around. Also a Mugen limited slip to put power down. It'll carry the inside rear about a foot in the air around higher speed sweepers.

erok

02-19-2002, 11:55 AM

If using a softer bar allows more body roll than stock, won't the suspension geometry be adversely affected? I'm no expert, but preparedcivic seems to have the right idea here. Stiffer springs should reduce body roll and eliminate the balancing and tire lifting problems associated with stiffer anti-roll bars. Right?

ConeKiller

02-19-2002, 01:00 PM

Ahhh yes, you are correct about the springs, but the Solo Events Board see's to it that we can't change those and stay in stock.

Rick

Jesse IL

03-06-2002, 12:20 PM

Sway bars affect handling by weight transfer, plain and simple. A stiffer bar translates more weight to the outside wheel during cornering. This increases the amount the wheel slips. With the front suspension on the Celica, roll will actually have very little effect on grip. Strut suspensions by their nature change their geometries very little if at all when raised or lowered. This is the big complaint with struts. That is why for handling purposes, you need quite a bit of negative camber on the front wheels. Roll however in the rear is a different story. The Celica has a double wishbone setup in the rear that not only changes camber dramatically when compressed, but also has a passive toe in when compressed. It is my feeling that controlling roll in the rear is much more important than controlling roll n the front. At higher speeds, the car can let go in the rear, but once the turn is initiated and the outside suspension compresses, the wheel on that side toes in and increases its camber. The car will suddenly catch, an unsettling feeling to say the least. i have to agree with Hotchkis's choice of going with a very large bar in the rear to limit roll and then using a front bar to offset some of the oversize nature of the rear bar.

ConeKiller

03-06-2002, 07:02 PM

Jesse,
First off the rear of the Celica Toes out under compression.

2nd, the front sway bar does more then affect weight transfer. And a stiffer bar does not put more weight to the outside wheel. The amount of weight on the outside wheel would actually go down with a bigger bar. What would happen is instead of putting weight straight down on the tire more weight (force) would be put in a horizontal plane perpendicular to the direction of the tire. (Thus the tires wanting to break free faster)...

Put it this way, with your theory if you put a really big bar, you would transfer lots of weight to the tire. That much weight and the car won't break free from the road. In reality the inverse is what happens. The larger the bar the 'less grip' you have...

I haven't described it well in type, it's easier in person..

Rick

Whiteline

03-06-2002, 10:30 PM

G'day there.

The ZZT231 Celica is quite a typical contemporary fwd drive in our opinion. Specifically the car is designed to push understeer with building power with a benign transition to oversteer on throttle lift-off or mid-corner braking. Not too much or this can cause total rotation (and backward exit).

However, unlike earlier fwd designs, the engineers have used some geometry tricks to provide some chassis feedback and make the car feel much more responsive, much more so than say an earlier generation Celica. Most of this comes from the rear roll centre height and its relationship with the front. With out getting too technical, the usual solution of disproportionate increases to rear swaybar size to combat understeer can deliver a "Jekyll & Hyde" personality at the rear during roll transition. This can feel like the car is moving between oversteer and understeer, as if it

GTS LAID

03-06-2002, 10:34 PM

hmm.. interesting... can you get too technical please i'd like to learn!

Jesse IL

03-07-2002, 10:19 AM

ConeKiller, you are right about the toe out, I realized that later in the day. What I said about weight transfer is right, from a certain point of view. You're right, weight transfer is in the horizontal direction, but the horizontal force is on the outside wheel. Adding a stiffer bar causes a greater amount of the horizontal force to be distributed to the outside wheel. Since total traction will only be affected by force in the vertical (normal) direction, adding horizontal force will cause the outside wheel to slip sooner, adding understeer (if we're talking about the front). After all, a car's handling condition is considering the case of the slip condition.

Whiteline

03-07-2002, 02:13 PM

G'day everyone,

GTS LAID:

Many new generation front wheel drive (and awd) platforms have been designed with a raised rear roll centre. This is not something you will find written up in the motor vehicle engineers handbook but as a result of our experience tweaking chassis's and suspension.

For example, the current WRX platform has had the rear roll centre raised by around 20-25mm compared with the previous. We can't comment on the previous generation Celica but the ZZT231 has an exceptionally high rear roll centre compared with the norm in that class of vehicle.

When we started initial development work on P-CeX, we started with corner weighting which showed up the very ordinary weight distribution. This was at odds with the driving impressions until we started investigating changes in the geometry and the roll centres. The relatively high rear roll centre creates a steep downward roll axis to the front which amplifies rear weight transfer giving the impression that the chassis is more neutral than it really is. Though it initially feels responsive, hight speed track testing showed that it was actually very nervous easily swinging between under/oversteer. Upgrading rear swaybar to combat initial front push would result in some nasty characteristics at the limit with the rear un-weighting dangerously so with lift-off or braking

Our solution was to create a roll centre adjusting kit for the rear to remove some of the artificial dynamics as we call them. Same as with our range of front anti-lift kits, we find it more useful to first remove the design tweaks that have been loaded in by the engineers to overcome the

pitcrew

03-07-2002, 05:00 PM

Whiteline, that's all well and good for a car that is raced in a class that allows major suspension mods. Most of us here autocross in SCCA stock class, which only allows adjustable shocks (only 2 adjustments max) with stock mounting points, front swaybar replacement using stock mounting, alignment adjustment only within the range of factory adjustability. No other suspension modifications allowed!

Whiteline

03-07-2002, 05:15 PM

Hi everyone,

Pitcrew:

I'm sorry but I wasnt really referring to any race class or rules. My post was purely in relation to the previous posts re swaybars and their effects on chassis dynamics. Apologies if this has caused any confusion.

As for the SCCA stock class, I'll help if I can. Are you allowed to change springs or ride height?

What does it mean by "2 adjustments max" to shocks, can you change bump and rebound separately across a range?

Cheers
Jim Gurieff

Whiteline

ConeKiller

03-07-2002, 06:46 PM

For SCCA Solo2 Stock Class...

Shocks, 2 independent adjustments Bump and Rebound, must utilize stock mounting locations, stock spring perches/location.

Springs, stock

Rear Swaybar, Stock

Front Swaybar, Open using stock mounting points

Rick

Whiteline

03-07-2002, 08:20 PM

G'day again,

Seems like the rules were developed by rear wheel drivers to suit rear wheel drives as this severley penalises front wheel drive platforms.

Assuming the rules are fixed, I would suggest doing whatever you can to stiffen the rear while softening the front proportionate to the rear. Some ideas:

- Increase rear shock bump rate and soften rebound
- Soften front bump rate and increase rebound
- Try using smaller front bar and/or rubber bushes
- Increase front camber to -2 or more.
- Use much higher tyre pressure in rear than front
- Trying using coil-wrap (insulating material we sell) around rear springs or anything else that is allowed to simulate increased rear spring/roll rate
- Use some toe out on both ends

Is any chassis bracing allowed?
Can you add some insulating material to the front spring perches?

Just some suggestions

Jim Gurieff
Whiteline

ConeKiller

03-08-2002, 05:06 AM

First off, I don't think your coil spring wrap would be allowed. Stiffening springs via spacers is not allowed.

Adding insulation to the spring perches wouldn't be allowed unless you lowered the spring perch the same thickness of the insulation. (Where the spring meets the perch must remain stock)

Chasis bracing is not allowed either... :(

autxr

03-08-2002, 05:18 AM

The rules are rather archaic, and were written when RWD was the norm. Back when these rules were written a Toyota Celica was RWD...

But your other suggestions are all things that we have been doing. Sounds like we are all on the same page.

I did appreciate the roll center, etc. analysis you gave of the Celica and will be curious to see what your whole suspension package looks like (I won't leave the car stock forever).

Much of what you say would explain why many folks that go with stiffer lowering springs are seeing dramatic changes in the handling (the car suddenly turns from a easy to rotate not very FWD like handling car to a typical, push in the turns FWD car).

Scott

CloNeGTS

03-08-2002, 08:33 PM

Whiteline,

Very interesting dialog. Very informative. I'd also love to see how your suspension kit(s) turn out.

Keep us informed.

Jesse IL

03-09-2002, 04:00 PM

Wow, I'm really interested in seeing the results of changing the rear roll center on the car. Thanks Whiteline. Also re-read the June 2000 SCC article about the suspension on their 300ZX. Very interesting, I'd suggest picking it up if you can.

Whiteline

03-10-2002, 01:39 PM

G'day everyone.

That is interesting. Increasing the stiffness of the rear is a way to overcome the inability to increase swaybar roll resistance. Lowered springs lower the roll centre which make a big difference on the rear, even with standard spring ratres.

We'll let you know when we have something more concrete to report that might help push the limits a bit further.

Cheers
Jim Gurieff

Whiteline

Raymund

03-10-2002, 04:46 PM

[QUOTE]Originally posted by Whiteline
[B]Many new generation front wheel drive (and awd) platforms have been designed with a raised rear roll centre. This is not something you will find written up in the motor vehicle engineers handbook but as a result of our experience tweaking chassis's and suspension.

For example, the current WRX platform has had the rear roll centre raised by around 20-25mm compared with the previous. We can't comment on the previous generation Celica but the ZZT231 has an exceptionally high rear roll centre compared with the norm in that class of vehicle.

When we started initial development work on P-CeX, we started with corner weighting which showed up the very ordinary weight distribution. This was at odds with the driving impressions until we started investigating changes in the geometry and the roll centres. The relatively high rear roll centre creates a steep downward roll axis to the front which amplifies rear weight transfer giving the impression that the chassis is more neutral than it really is. Though it initially feels responsive, hight speed track testing showed that it was actually very nervous easily swinging between under/oversteer. Upgrading rear swaybar to combat initial front push would result in some nasty characteristics at the limit with the rear un-weighting dangerously so with lift-off or braking

Our solution was to create a roll centre adjusting kit for the rear to remove some of the artificial dynamics as we call them. Same as with our range of front anti-lift kits, we find it more useful to first remove the design tweaks that have been loaded in by the engineers to overcome the

Whiteline

03-10-2002, 05:47 PM

G'day,

Raymund:

I tried to have a look at that link but its in Japaneese, is there an alternative? The pictures seem self explanatory though.

That's interesting about the Corolla?celica sharing a platform, this is our first foray into contemporary Toyota chassis's so we're still learning. Calculating the rear roll centre is a bitch and the extend of angular change through the working arc is quite interesting too.

Cheers
Jim Gurieff
Whiteline Automotive

Raymund

03-10-2002, 06:13 PM

I've stumbled upon another site with better expanations. i'll see if i can find it again.

btw, the corolla uses Mc struts all the way around.

Raymund

03-10-2002, 06:36 PM

"Just like active rear steer systems, they are useful for enlarging the median performance envelope however sometimes at the expense of outright predictability and handling for enthusiasts."

The generalization you've made about active rear systems definitely applies to the celica. As you probably already know and is well published, the celica rear has a toe in/out geometry. Toe in during suspension droop and toe out during compression. While this design shows certain advatages like toe-in braking stability and passive steering during corners. I've found this set up to interfere with the driver and tire grip communication. it gives a false impression the rear tires are sliding were in actuallity the tires are just pointing out. in order for this to fully work lots of suspension travel is needed. thats were soft springs comes into play to allow the passive steering geometry to work. i've found this problem can easily be tamed with a stiffer suspension. springs/swaybars.

i hope this helps.

M SPEC

03-11-2002, 05:26 AM

Jim (Whiteline), Glad to see you on here after the email I sent you about the site a couple of weeks ago. This is by far the best current shape Celica site on the net. Looking forward to your ZZT231 handling and other kits when they are released. Keep up the good work.

Jason

Korben007

03-11-2002, 09:43 PM

Hey,
where could I go to college to learn about all this stuff is this what a mechanical engineer does? or is it something else
thanks

MilinGTS

03-20-2002, 01:02 PM

would the inside rear wheel spinning problem be present with my LSD equipped celica gts?

it didn't seem to be an issue...but the car had an odd habit of having to be "Steered twice"

once id turn...then the car would be turning to little and id have to readjust.

pitcrew

03-20-2002, 03:59 PM

Originally posted by MilinGTS
would the inside rear wheel spinning problem be present with my LSD equipped celica gts?

it didn't seem to be an issue...but the car had an odd habit of having to be "Steered twice"

once id turn...then the car would be turning to little and id have to readjust.

Did you put in an LSD?
One of the reasons given for manufacturers not equiping FWD cars with an LSD is that they torque steer.

ZeroGTS

03-20-2002, 05:49 PM

it felt like more of a spring thing. id still be having traciton...but the car would dip one way....then it would settle and into the turn it would need a tiny bit more steering all of a sudden.

im using pro kits.

it feels a little odd.

there wasnt squealing when this happened.

yes i have an LSD

autxr

03-21-2002, 04:33 AM

Eibach pro kit...

In other words, they are variable rate springs. Maybe turn in on soft spring, then turn in again on the hard spring.

That's why I tell everyone not to get veriable rate springs. Zero/Milin- what shocks are you running? Another very possible option (other than having 2 spring rates) is that you are bottoming out. Typically the way that feels is an instant push when the suspsnsion hits the bump stops, but maybe not if you weren't already at the limit.

Scott