Sway Bar Delete

[Advancedynamix]

^Good to know. I have Aspire KYBs for mine, but I'll keep that in mind for the future.

There is a drastic difference between the aspire KYB and the MK1 vw kyb shock.

[sketchman]

Well for now I have brand new ones to use, so I'll make the best of it. I will shorten them, though, and throw in some VW bumpstops.

I'll also have Rio front struts, so that should help a bit too. Next time I'll do Neon fronts and VW rears. Live and learn.

[TorqueEffect]

Dang it, where was this info when I bought Festiva KYBs? What does it really take to install the vw KYBs? And I assume mk 2 golf?

Sent from my LG-D800 using Tapatalk

[Advancedynamix]

once again, an interesting explanation and food for thought, using the non-multi tasking rear suspension do more than just go along for the ride. i wonder, if you are using the rear to control roll, would it be beneficial to stiffen the floor pan/boxed sections of the body to more directly transfer some of that roll control to the front, or is some amount of body twist desireable? if it was available, would a 20mm front swaybar be a performance upgrade?
kia shows a different swaybar part# for the 1.1L prides. i thought it might be thinner but the bar bushing # is the same for both the 1.1 and 1.3L cars. maybe the 1.1 bar is hollow. 4GREEN shows both at a reasonable price. except for shipping

Maybe. The problem with a softer bar is that the front sway bar on the Festiva also acts as a shock load absorbing trailing link. It's actually a genius design. So simple and light and effective. However, softening this means you'll get more distortion under acceleration and deceleration.
Take a look at your sway bar where it goes from the body mount to the control arm. Notice the arc, to clear the wheel as it articulates for steering? That arc also works as a spring. That bar is made of spring steel, like a leaf spring. The arc helps dampen the driveline for better traction while accelerating and braking. If you change the rate of that spring, you change the dynamics of the chassis under acceleration and deceleration.
Watch videos of high hp Festivas on a load bearing wheel dyno and you can see the front wheels move forward. The flex is useful to a point, but excess flex will cause the car to TQ steer and loose traction due to the change in toe ( it toes out under acceleration).
As far as stiffening the chassis, I don't see any need to stiffen the chassis of a Festiva other than the front lower radiator support. I have repeatedly pushed one of these cars past 3 lateral G's without added rigidity and didn't encounter any fatigue or signs of excessive chassis flex. According to SAE safety documentation, the Festiva chassis is one of the most rigid (by weight) chassis ever sent to this country. This was Researched and reported to me by Larry Pond. It's not a coincidence that I chose to build these cars.
With that being said, chassis flex is important. The chassis is the most important component in a suspension system. Not only because it holds everything together, but because it's flex is ultimately what keeps the tires planted firmly on the ground. Adding rigidity without a complete understanding of the dynamics of the structure could not only reduce the cars ability to conform to the driving surface, it could also weaken the chassis do to a change in the way the load is distributed . I've seen braced and stitch welded race cars (these were Porsche cars, not Festivas) fail much sooner than the same chassis which had not been prepped. Possibly the best example of the chassis working with the suspension is in Formula1. More money, time and effort has been spent developing these latest f1 chassis than has been spent putting man into space. The chassis of an FI car is not rigid, it is designed to flex and control frequency loads on the absolute limit of wheel driven performance, while also keeping the driver safe from absolute disaster.
Though it's certain that Mazda didn't have an F1 budget to design the Festiva, they did have a very qualified group of engineers who were doing their best in an extremely competitive market. The mid to late 80's were the heyday of the hothatch, with many racing programs focused around small hatchback cars, and a world market that was flooded with sporty, economical compact hatch's. Mazda has a strong history of innovative and successful designs, as does Ford. It's no wonder that the 121 chassis is so amazing. What I often wonder about is how it has remained such a secret.

[F3BZ]

thanks once more for taking the time to explain in layman's terms these dynamics. i'll definitely buy a copy of your book when it comes out. why is the lower radiator crossmember an achilles heel? is the gage too thin? this piece is one of about a dozen stampings of the body that is made of high strength steel. if you remade it to be beefier, would you still use high strength steel?
F1. starts with an F. festiva. starts with an F. coincidence?

[Advancedynamix]

Formula 121 = Festiva hehe.

The front lower radiator support is the most stressed member of the chassis under acceleration and deceleration. The wheels push the car via the front sway bar. The sway bar mounting plates are held by the front lower radiator support.
With the loads applied by the stock B3 and 155/12 tires, the front support is plenty adequate. If you plan to put over 100ft.lbs of TQ to the ground, I strongly suggest replacing this support with something that is not only more rigid, but also secured to the frame rails better.
My best guess, as to why this area is so flimsy, is that this is a crumple zone issue. Auto manufactures have to make cars that squish just right to keep the occupants safe. This area of the car is quite squishy.

[Safety Guy]

Charlie, one thing I've noticed on my "Northern" cars is that the front stab bar ends get all corroded underneath the bushings. I'd love to have new front bars, or a nice rust free southern bar, but would it be best to have the eaten out areas of the old rusty bars completely sandblasted and then welded back up to spec diameter or is this even a concern?

Also, if we were to make a bunch of new front stab bars, what would be your ideal specs for say, 100 to 150 hp road race/daily driving (as opposed to just drag race) usage?

Karl

[sketchman]

He said welding wasn't a good idea. I'm making drag links, and I'll post up pics when I get them done.

[Advancedynamix]

Charlie, one thing I've noticed on my "Northern" cars is that the front stab bar ends get all corroded underneath the bushings. I'd love to have new front bars, or a nice rust free southern bar, but would it be best to have the eaten out areas of the old rusty bars completely sandblasted and then welded back up to spec diameter or is this even a concern?

Also, if we were to make a bunch of new front stab bars, what would be your ideal specs for say, 100 to 150 hp road race/daily driving (as opposed to just drag race) usage?

Karl

Karl, welding spring steel makes it brittle, so this would actually weaken the area your trying to strengthen. Also, trailing links, or drag bars as many call them, aren't specifically for drag racing. In fact, these trailing links would be substantially more beneficial on road going cars than they would be on a race car. Proof of this is in the last generation of Kia pride with this style of front suspension (01-05 Kia Rio is actually a Pride). The "New Pride" uses trailing bars to support the longitudinal load, rather than the sway bar. These cars have a separate sway bar instead of integrating it. Basically, the Festiva evolved into the system that I'm describing.
I will eventually build a trailing link setup for both of my Festivas.

[Safety Guy]

Are these trailing links considered torsion springs? Just wondering.

Karl

[Advancedynamix]

Are these trailing links considered torsion springs? Just wondering.

Karl

No, a torsion spring is the spring which loaded by twisting it. The trailing link is not technically a spring, though it's flex should be considered when it is being designed. The trailing link shouldn't be torsionally flexed.

[sketchman]

I wondered about the flex.

With a straight link from control arm to stock sway mount point you have an angle at the control arm. The stock bushings might be preferred in this setup because they would allow greater flex and so be easier on the link, and assuming a rod end at the frame end, you'd also probably balance out the loss of the compliance up front with stock bushings at the control arm.

I plan to run the poly bushings at first and see how it feels.

[blake4591]

I read through this thread about a week ago and have been thinking about a couple options for the sway bar since I have to figure out what to do on the car I’m putting together. First has anyone investigated simply using the Rio traction arms. They are available on rock auto new so I will not have to pull a bunch to find ones that aren’t rusted under the bushing as Karl was describing. I know the control arm and bushing is a different width but I’m sure a spacer could be made to take up the extra space between the nut and the bushing washer. I’m planning on strengthening the rad support so it shouldn’t be much additional work to integrate a solid mounting point for the rio trailing arms. This also gives the factory part and appearance that I’m going for with the build. The second though I had was trying to reduce the torsional stiffness of the factory sway bar. I wonder if it would be possible to cut the arm in the long straight portion and then sleeve it with a tube that has sealed bearings or bushings in it. This would in theory remove all the sway function of the bar and make it only a trailing link. Just sort of thinking out loud here.

[sketchman]

If you use the Rio part or the trailing part of the stock bar you still have the spring effect of having a bent bar taking longitudinal forces.

IMHO it would be better to have a straight bar and change the bushings to tune the stiffness to your liking if you plan to make power. If it's a more stock build that sounds like a great idea to me.

[Advancedynamix]

The Rio bars are too long to fit under a Festiva, IIRC. I would have already done this if they fit.
Also, the spring action of the trailing link is beneficial in putting HP to the ground. The stock bar works great up till the 180-200ft.lb mark, then it distorts too much and affects the wheel alignment, which affects traction and can cause torque steer issues. If you don't plan on using more than 180ft.lbs of TQ (about the same speed as a c5 zo6 corvette) then keep the stock bar and get poly bushings for it from Australia. If your dead set on removing the bar (like I am) then be aware that flex is important in a chassis.