Can I keep up with vettes with my leaf springs?

[CamaroJesse]

ive done alot of reserch into leafs and handling with them and it sounds like they do really good if set up properly. but if i set up my camaro just right, could it keep up with vettes as far as handling goes? im talkin modded suspension vettes. by the way i got a 68 camaro. and as of now it has dse springs.

thanks
jesse

[zbugger]

...im talkin modded suspension vettes....

HIGHLY doubtful. Unless you have enough horsepower to keep up in the straights.

[DarkoNova]

Maybe a stock one, but not modified.

Maybe if you had fiberglass springs with those pivoting bushings, you'd fare better, but still doubtful.

Matt

[Lowend]

Any time you go up against a car with IRS on a non-smooth surface you are at a pretty huge disadvantage.

It really depends on the specifics of the car you are up against and the surface you are running on.
If you look at the SCCA standings Superstock - where you find STOCK 2002-2006 Z06's on race tires and good shocks runs almost as fast as CP which is the home to big tire'd big HP live axel cars.

[Derek69SS]

Not unless the 'vette owner can't drive.

[sporter]

Depends. The most important part of any race car is the driver. A very skilled racer in an average car can embarrass an average racer in a high $$$ car. Given equal drivers, my money's on the IRS. :usa:

[David Pozzi]

The vette has a lower center of gravity, plus better front to rear weight balance. Early vettes suffer from lack of wheel room unless you flare the heck out of them, but the newer cars have some basic advantages. The IRS isn't going to be an advantage on a race track, unless it has a lot of bumps, and most don't.

[CamaroJesse]

well here is my suspension set up as of now. DSE rear springs(175#), hotchkis front springs(600#), ATS tall spindles, probably going with bilstein shocks, i will get a sway bar in the front and maybe some type of panhard bar or a watts link for the rear. fat tires all around and its caged so the frame is nice and tight. How should this car handle? im worried it wont handle like i want.

[wendell]

Pretty tough question to answer. The '68 that I've been developing with the owner will take a new vette to court. That's with leafs,a 4 speed and an iron headed 302. Doesn't mean yours will.
I think the single most frequent mistake I see on the board is this; folks think that going threw a catalog and ording a magic list of parts will make there car "handle like it's on rails" or be faster that a corvette. It won't. Seat time, data and attension to detail will. There is more speed in you mind than your check book.

All that said, it looks like you've spec'ed a good foundation to start from (except for that giant block of iron up front). Have fun with it.

[6'9"Witha69]

I was tagging a new vette (non Z06) up a mountain road last Friday. I have leafs and this thing sticks. I still have a LOT of adjustment to do and more stiffening. Leafs can perform. Never count them out.

[CamaroJesse]

6'9"Witha69- whats your suspension set up? and how do you go about adjusting and stiffiening without coil overs?

[ITLBTU]

How did you hook up the rear sway bar with the leaf springs? I bought one years ago, but I couldn't figure out how to mount it, so I sandwitched some thick flatbars on both sides of the leaf, and then attached the swaybar to that on both sides. I know that isn't the correct way.

[6'9"Witha69]

My setup is pretty simple. Hotchkis springs F/R. Matched Bilsteins F/R. CE Slide-A-links with about 1/4" gap and the solid front eye bushing that comes with it. Urethane rear eye bushings. GW upper and lower arms with del-a-lum bushings up front. 1 1/16" solid bar up front with Energy Suspension 9.8120 end links and ES greasable bar mounts.

There is a lot of adjustment in just how tight and what type of end links you use. Alos playing with the outer tie rods for bumpsteer settings. There is also fooling with alignment settings. I will be buying tall ball joints and seeing how that works. I am also going to switch the CE boltin SFCs for GW weld-in. I have them, just haven't installed them yet. I have considered adjustable shocks, but that will be further down the road.

[Lowend]

Jesse - without a doubt you are going to have a fun street car, and that is what really counts.
If you are running a C6 up a mountain road with an equally skilled driver at the wheel; than you'll have problems... just like most of the $100K+ exotic cars in the world. Frankly there is no shame in it.
wendell is dead on...
One of the things I have always loved about my '71 is the fact that it's ugly and relatively cheap... with all the tuning over the years, and me at the wheel its a fearsome competitor.

[David Pozzi]

You will need a front and rear anti-roll bar and some work to balance the oversteer/understeer.

[CamaroJesse]

well im going with a front sway bar. what brand is good? and as far as rear sway bar i didnt even know i needed one. should i do a sway bar or a watts link for the rear?

[wendell]

A sway bar and a watts link have nothing to do with each other. Again, throwing a catalog at a car isn't going to make it fast. I truely respect David's opinions on tuning 1st gens. That said I'm a little surprised at the recogmendation of a rear anti-roll bar. A properly spec'ed set of leafs should provide enough roll stiffness to negate the need for a bar. The exception may be a VERY soft bar with a lot of adjustability to fine tune the roll couple.
But again, David knows what he's talking about.
p.s. I've heard rumors that Lowends car screws.

[silver69camaro]

A properly spec'ed set of leafs should provide enough roll stiffness to negate the need for a bar. The exception may be a VERY soft bar with a lot of adjustability to fine tune the roll couple.

I'd have to disagree with the first part, but I do agree with the second. Not all leafs provide the roll stiffness that is needed in the rear. Bushing type and spring material (composite?) play big roles in this, as you know. My car needs a bar that's about 1/2" diameter, but then again, I'm not using steel springs.

[Takid455]

how do you go about calculating the required dia. for a sway bar? I know how to calc the stiffness, would like know how to find the required stiffness.

[zbugger]

That's a tough one. Basic rule is, the stiffer the spring, the less bar you will need. BUT... The wider the tire, in relation to the front, MAY dictate more rear bar. It also depends on your driving preferences as well. If you prefer a car to push a little, settle for a little less. Like a looser condition? A stiffer rear is better. It's actually pretty difficult to settle on one bar. That's why a sway bar is recommended to be used as a tuning device. But it takes a lot of variables to figure out just what you really need.

[silver69camaro]

how do you go about calculating the required dia. for a sway bar? I know how to calc the stiffness, would like know how to find the required stiffness.

That's where you pick up a copy of Race Car Vehicle Dynamics and starting reading and going through the numbers.

With those equations, you can get pretty close. That is what I used for Art's '60 Vette, and it perfomed very well out-of-the-box. A little tuning would have helped, but we didn't get the opportunity and we're happy with the results.

[Lowend]

I would touch base with the boys at ATS, they certainly have done a few suspensions based around their spindles and the DSE springs, they could give you a baseline to start with for swaybars.

Performance Trends makes some excellent software for suspension design and planning as well

[zuess4u]

Also...speak with Marcus at www.SCandC.com (http://www.SCandC.com) discuss the Fays2 Watts link.

[wendell]

Silver,
Duely noted. I don't have any experience with composite leafs but depending on the arm length a 1/2" bar could be classified as very soft for fine tuning the roll couple. Cool cars.

[David Pozzi]

wendell,
I am editing in this preface.
We wanted to start out with a fairly "known" system to get the car handling well right from the start. I chose the Hotchkis TVS system mainly because I liked the hollow anti-roll bars and figured we could change spring rates if we didn't like them sometime later. Expected use was street driving, perhaps some autocrossing, and at least one open track to see if my wife liked it. (Boy did she like it!) We initially found the car to handle great but after a while found the car to be leaning too much, a bit low in the rear, and soft in the rear, also the Hotchkis Bilstein shocks were great on the street but at an Autocross I could feel that they were way too soft and allowing the car to "flop" over on corner entry. Many of the problems showed up when we switched from street tires to DOT race rubber, the Kumho V710's and was the result of the added grip they provide.

My wife's 73 has taught me a lot about rear springs lately. We went from a complete Hotchkis TVS kit to adding Global West rear leafs. The Hotchkis leafs are 175 lbs, the GW are 240 both by my measurements at home. I measure by placing each end of the leaf on turntables, then loading it with as much weight as in the car, then measure one half inch each way, up and down to get 1" travel. I use a hydraulic gage like a valve spring tester.

Anyway, with hotchkis, the car was very balanced with a little bit of understeer, not bad at all. GW advised us to not use the rear bar. The result was terrible understeer and lifting of the inside front wheel 2"!

We reinstalled the rear bar and the car was balanced! What I learned was the Hotchkis spring had rubber front and polly rear bushings at a torsional stiffness of 27 ft lbs/deg for each spring and will easily twist to 9 degrees. The GW leafs are the Cat5 with spherical bearings and ZERO roll stiffness due to bushings. The GW springs also raised the rear a little which was desired, aprox 1" so there was probably a small roll center height change.

I learned spring rate has a much smaller effect on roll resistance than bars do. I still need to play some "what if's" and see what a 100 lb stiffer spring does to roll couple compared to a 1" rear bar change. The bar seems to do way more than the spring.

According to my Performance Trends Suspension Analyzer program, total roll stiffness is now at 4181 ft lbs/deg. That's .8 deg predicted roll at 1G but I'm sure the car is rolling more than that but probably not much more than 2 degrees on normal turns now. The program makes it's calculations based on the assumption that the antiroll bars are mounted in race car solid mounts with heim jointed ends. Ours are poly mounted with poly end link bushings, so the actual roll resistance is always less than calculated. The car has been measured last year at Button Willow at 1.2G lateral by data acquisition, with peaks even higher than that for very short periods.

To get balanced handling with no rear bar, we would have to either use solid leaf spring bushings or reduce front roll couple a lot. I think something like 74% front roll couple is needed for our 73 Camaro with 54% front weight percentage. With no rear bar, we have 89% front roll couple which is the way it was when the photo below was taken.
David

Here is the car with GW leafs and no rear bar:
https://static1.pt-content.com/images/noimg.gif

[wendell]

Thanks for the info David. A picture's worth a 100 words and that pic is a rousing endorcement for a rear bar. You knowthe sort of thing I'm into over here and we're able to tune a lot with rear rollcenters.

The '73 looks awesome!

[silver69camaro]

I LOVE that photo!

[David Pozzi]

It pretty well shows the front was doing way too much work! :)
I was not at the event, and Mary didn't realize that the car was doing that, she just said it had terrible understeer. I was doubtful that we could get by without a rear bar, but we had to start somewhere and used the GW recommendation as a starting point.

From a driver's standpoint one of the biggest improvements was the "G" braces invented by Herb Adams, Alston and others sell them now. The car responds much more quickly now to steering inputs.

We have a lot more weight to control and need a lot of anti-roll bar stiffness to keep the car from rolling excessively, with leafs we can't do much about roll center height. I have to say we have no corner exit traction problems once we are in second gear, which is most of the time unless there are super tight corners. Our second gear would be equal to a Close ratio Muncie and 4:10 gearing. We have 366 hp at the rear wheels.
David

[ITLBTU]

It pretty well shows the front was doing way too much work! :)

From a driver's standpoint one of the biggest improvements was the "G" braces invented by Herb Adams, Alston and others sell them now. The car responds much more quickly now to steering inputs.

David

Dave, Does Herb Adams have a web site? I've searched and I can't find it.

[millis]

Herb Adams has a book. Year One part # MJ38.

Year One link - Herb Adams, A Leader in his Class (http://www.yearone.com/leader_ads/herbadams.html)

Link to book on Amazon (http://www.amazon.com/Chassis-Engineering-HP1055-Herb-Adams/dp/1557880557)

millis

[David Pozzi]

Alston calls them "Firewall braces"
http://www.alstonracing.com/pdf_catalog/CATALOG_24.pdf
Mary bought them from a guy on nastyZ/28 called protourFbody or something like that. I'd have to get the exact name from her. I"m not sure who made them, hers are black, not red.
David

[Jeremy]

Most likely she got them from Pro-touring f-body.com. He is where I got mine. Mine is a t top car and I found that they can be improved by connecting both sides. I have a cross brace built out of one inch tube steel connecting both sides (the actual brace is 1 by 3 but I can go as big as 1 x 4 without clearance issues). I was hoping it would take some of the load off the firewall and it has. With a solid roof car this may not be an issue, but it is pretty cheap and easy to try.

[jeffandre]

Most likely she got them from Pro-touring f-body.com. He is where I got mine. Mine is a t top car and I found that they can be improved by connecting both sides. I have a cross brace built out of one inch tube steel connecting both sides (the actual brace is 1 by 3 but I can go as big as 1 x 4 without clearance issues). I was hoping it would take some of the load off the firewall and it has. With a solid roof car this may not be an issue, but it is pretty cheap and easy to try.

Pics of this cross brace please!!! I was thinking of using 1/4 iinch by 1 inch strap on the upper cowl part, enough to make up for the lip height. The strap would span enough so that both braces would bolt to it.

[Jeremy]

I'll try to post some pics this weekend. I tried a piece of 1/8 inch plate that bolted to both braces and it worked but when I took it off I could see were the plate actually bent slightly just inside the braces. There was a real nice straight line 1 inch in from the outside edge of the plate.

I then laid a piece of 1 x 2 across the upper bolt holes I made and this added a lot more resistance. I figured if that was good, more would be better. I ran a piece of 1 x 1 below the 1 x 2 and can also add a piece of 1 x 1 above it. The lower 1 x 1 is bolted through the braces like the 1 x 2. I plan to weld the tubes together at some point and cap the ends. I could have gone with 1 x 4 tube but I figured the extra walls would be stiffer than one big box.

I can also drop some legs done around the air cleaner to bolt to the arms a lot closer to the a arm mount. Since these will be angled it should add even more torsional resistance.

In street driving I have nary a rattle or cowl shake. The car feels really solid. I am trying to get rid of a few creaks and groans in the roof just above the windshield. I only hear these when I hit driveway cuts at an angle, but want to get rid of them anyway. It may not be possible as it is a t top car, but it doesn't cost much for the steel and I enjoy fabbing it up.

I have also heard that the t top cars can pop some of the spot welds leading to noises. I plan on pulling the headliner one of these days to see if that is the case.

Overall, I agree with Dave that the braces are well worth the money. I had some issues installing them as well, but the passenger side was worse for me. I had to pull the AC compressor as there was no way I was gettng it in there with it in place. I tried for a couple of hours. When I had the AC evacuated and unbolted the compressor, it did not take much time. All I had to do was lay the compressor up on the intake and valve cover a bit. I didn't have to un do any lines.

[David Pozzi]

Here he is:
http://www.pro-touringf-body.com/chassis_components.html

[O'Neall]

David... would you say that the GW 240# leafs with a rear bar was about equal in roll stiffness to the Hotchkis leafs with a rear bar? (I ask because you mentioned that the GW springs didn't offer much roll stiffness due to the spherical bearings.) Or did the GW/rear bar combo eliminate that bit of understeer that was present with the Hotchkis leaf and rear bar?

Curious to know.

[David Pozzi]

Yes, I was quite surprised to find we needed the same Hotchkis rear bar for the much stiffer GW leaf springs. The difference is the Spherical bearings. Quite a surprise.
David

[ks71z28]

Dave,
I agree with your recomendations of using the sway bars to control roll, I guess that's why there called anti-roll bars! I have had great luck with my old Rancho Suspension adjustable sway bars. The end links front and rear slide, and effectively change the lever arm on the side of the bar. I used to have both bars really tight, that along with urethane bushings allowed almost no body roll. I found out that the urethane was causing binding in the suspension movemnet, which caused the car to be skatey over corner bumps. Del-a-lume bushings and greasable swaybar pivots fixed that! Adjsting the bars is really nice. I set body roll for weight transfer with the front bar mostly, then adjust the rear for over/understeer. I sure would like to spend a day at Thunderhill with you and Mary. Mary is an animal, that picture above is great!

Keith

[ks71z28]

BTW the Ranch bars are 1.25" front, and 1" rear. The adjustability is like adding or subtracting 1/4" from your sway bar diameter without removing the bars. Dave, How did you guys get 366 RWHP from that crate motor?

Keith

[David Pozzi]

It's the GM ZZ425/383, no special parts other than that. It's built for torque with a dual plane manifold which is nice. We did a couple of dyno pulls after installing the new X pipe, Walker mufflers and Flowmaster tailpipes. It's 2.5" all the way back now, before we had 2.25" pipes with flowmaster 50 series. We had to richen it way up after the exhaust change, like 6 sizes at all four corners!
David

[chicane67]

Seat time, data and attension to detail will. There is more speed in you mind than your check book.

...and dont forget to get some "magic pixie dust" that the tech haters talk about.