Bigger Front Swaybar
 

Does anyone out there know where I can get either a 1 1/8" or 1 1/4" diameter front swaybar for a late ERA chassis ?? The stock one is 15/16" .... and while perfectly adequate for the street , I would like to get something a little bigger for the track and I don`t mind at all a rougher ride on the street .
FWI .... shocks , springs , camber , alignment , ride height etc are also all being changed . That`s what happens when you read the tires after a weekend of track time !

Bigger Front Swaybar
 

That bar size seems very big, with my limited knowledge of suspension I would first increase spring rates, valve shocks to suit springs.
Castor then approx camber etc before I increased roll bar stiffness!

Try the car first, and if you cant find a roll bar that size get some appropriate steel and bend it yourself and have it tempered.

Ant .... that was my first thought ... stiffer front springs , until I talked to the guy who does all the suspensions on several vintage race cars and a TransAm car . He also does the suspensions on several Vintage NASCAR stock cars here and his own circle track car . I`m not saying he is infallible , but his thought was stiffen up the roll and keep the front springs relatively soft . At the same time , go to shocks that were adjustable on both compression and rebound and matched to the springs . Lets just say I had some hi speed stability issues on the dog leg on the front straight at VIR .
Caster is 5 degrees and camber will be increased ( more negative ) on both front and rear . He said all their cars run about approximately 1/16" toe out on the front and about the same on the rear ... except toe in there .
I was able to get just under 200 miles in at VIR and was able to get some pretty good tire readings as to wear patterns .
Thanks for your suggestions as I`m looking for all the help I can get .

Bigger Front Swaybar
 

Bobcat,

Sounds like you are on the right track, that makes sense to me.
I have on my Ram, fully adjustable Bilsteins that were custom made so I can adjust valving to different springs. I really wanted Konis but was talked out of that by a Bilstein enthusiast as he reckoned keep it simple, they cost me almost as much as Konis top of the line race shocks. My sway bar is about 1" although my car is still in the build process I have all the trial and error stuff to come!

Castor is much the same. and I guess you just crank on more camber until you get the happy medium in temp and tyre wear!

Best of luck.

There's two trains of thought with the front suspension. They're both valid, and both work. But they do work a little differantly.

Soft springs and big bar: The soft prings allow the suspension to maintain contact with irregular pavement (which is the suspensions job), and allow the CG to shift to the front during hard braking. But the large bar controls body roll in the corners.

This works well in a bigger/heavier car. But not as well in a much lighter car like a Cobra.

Big springs and soft bar: The springs control the suspension, and control the body roll. The sway bar is used to fine tune the wheel rates for varying conditions. This works well with a light weight car (and especially on IRS). The down side is, it can provide a harsh ride on the street.

Have you calculated your suspension frequency yet? What about corner weights? You might be surprised at the recommended spring and bar rates.

Most track cars have a weight bias to the front. But many Cobras (like mine) have a weight balance to the rear. This really changes your set up. Sometimes people who work on Mustangs and MG's don't realize this.

Bob ... thanks for the input . Haven`t calculated the suspension frequency yet, but have had the car`s corner weights set . Like yours , I have more weight on the rear than the front ( 52.5% ) and cross weights are all within .3% All weights/settings were made with my weight in car and just under 3/4 tank of fuel and all other fluids in . Interesting point on the cars that he works on and I`ll ask him about that today . BTW , I have the ERA IRS rear suspension .... and most of his cars don`t .
His comment about softer front springs made sense to me as that`s how I had my dirt car set up years ago .... as soft as I could get it and still keep it under control ( most of the time ) .

Bob

Bobcat,

Do the frequency calculations first. You'll find that the car is initially set up with a pretty strong difference between the front and rear (by design). I recommend that the springs be changed rather than the anti-sway bar so that the lift under acceleration is reduced, and therefore reduced camber change. This will decrease the amount of power-on understeer/lift-induced oversteer you get.

Soft springs and big bar works really well on a dirt car. The soft springs control the suspension over the irregular surface and keep the tire in contact with the racing surface.

This is not a dirt car, and you'll be driving/racing on a much smoother surface. So those concepts don't apply all that well.

I use 650# springs in the front, and a modest bar rate. That seems to work well, and we get pretty flat cornering.

I also have IRS, and that's a whole differant ball game. The IRS should be prdominantly controlled by springs. With either no bar, or a very light bar for fine tuning. If your springs are set up just right, a bar will actually degrade handeling.

But the way my IRS is built (and probably yours too) it's almost impossible to fine tune with the springs only. The motion ratio is just too high. It can be done if you move the springs as close to the tire as possible, and straight up and down.

Those caster and camber changes should have very little effect on the car in the small picture. If the changes are huge they will. Otherwise they are expected and desired. It's the toe out changes on compression (bump steer) that can really get you!

I don't know the exact numbers for the ERA cars, only mine. But to make intelligent decisions you need to collect data before making changes. Find out what the unsprung weight is at each corner. Calculate motion ratios. Measure sway bar rates. Once you have all that data, it's easy to plug the numbers into a spread sheet, and see what happens when changes are made.

The spread sheet is not magic, and will not provide all the answers. But it does get you in the ball park, and help you understand what happens when changes are made. It's a very helpfull tool.

On my car, I'm using 650# front, and 750# rear. I'm considering 850# rear, and 750# front. It looks good on paper. But I'm not sure track testing bears that out. I'll consider it again when we race in a couple of weeks.

Another note on springs. There are $5 springs, and there are $50 springs. You get what you pay for. There is a noticable differance between one and the other. I use $50 Eibachs.

BTW, I am not a suspension genius nor Guru. I credit Gordon Levy, Wayne Presley, and Carroll Smith for educating me, and helping me to make intelligent decisions. So far, it is working well for my car; it keeps getting faster and smoother, without wasting a bunch of money. A bow of thanx to my friends. :)

Bob:

I'm interested in your source for the $50 Eibach springs..

Thanks,

- Allen.

Got mine from Gordon Levy, about 18-24 months ago.

I have'nt seen anybody point out that in anti sway bar selection, the idea is to balance the front (geometry) roll stiffness RELATIVE to the rear (geometry) roll stiffness. The key word is "RELATIVE".

My 2 cents.

Very true; front and rear have to work together. That's why I asked about corner weights and suspension frequency. Especially with a light car, IRS, and a rear weight bias.

Speedway sells roll bars and different diameter
 

Bobcat Speedway sells straight bars at different widths, ratings, and sizes of the bars. They go by the 1/16 of an inch. You will need to modify the frame mounts and custom set of arms to hook to the lower control arms. They are adjustable with a spline ends. Hiem joints are used for the connection. I believe that Morris and Cobra 3170 are both running this setup. 18" wheels are on these cars with serious suspension changes. Rumor has it that they are running about 1,000 pound spring in the front and 1 1/16" roll bar. Don't remember the rear rates. Seams that 900+ to 1,100 pound springs are what the faster guys are running on road course and autocross. Car rides like a tank but handles like F1. Rick L.