jon
Unregistered User
(7/8/04 11:07 am)
Reply x
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correction:i tend towards OVERsteer.

chicane67
Registered User
Posts: 133
(7/9/04 6:06 pm)
Reply | Edit Re: x
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FYI, I'm not ignoring this, I have to put some though into it. Moving weight around takes a few brain cells and I am spent from work right now.

Give me time for a Vegas Robaina and an 18 year.......and I'll be prime.

CarlC
Registered User
Posts: 190
(7/9/04 6:21 pm)
Reply
Re: x
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.......and I'll buy a round of said 18 year the next time I'm in LV for work. Likely early August or early Sept.

David, the car definately understeers under steady state cornering.

Looks like we hijacked Adam's post (sorry Adam.) Perhaps it's more appropriate to start a new topic. If so can Ralph move the info into a new thread?
http:www.geocities.com/casanoc

Edited by: CarlC at: 7/9/04 7:07 pm

ddennis68
Registered User
Posts: 225
(7/9/04 6:43 pm)
Reply hijacking
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i cant speak for Adam but I don't hink he minds, the wealth of knowledge especially in the suspension forum is unbelievable-getting off topic is inevidable and almost always worth it. Keep going guys.

davidpozzi
Moderator
Posts: 1224
(7/9/04 8:11 pm)
Reply
Re: What are you running for a rear sway bar?
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Quote:
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While you're at it, can you describe how tire/wheel width has an affect on that too?
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As Tom said, lots of variables here.

Wider wheels and tires add more (relative) cornering traction to that end of the car, and also make the springs and bars less effective if the wider wheels results in more outboard offset. Either way, wider tires with more wheel offset wil add traction to the front, resulting in oversteer if the car was neutral before, if you do the rear, the rear sticks better and the front will understeer.

Go-Karts can can add oversteer by pulling the rear wheels in or moving the fronts out.

If you start out with a full gas tank and the car is neutral, when the fuel burns down to a quarter tank the rear springs and bars are now stiffer in relation to the load they had before, the car will go into oversteer and lose traction coming out of turns, especially slow ones.



I used a rear bar on my 67 for autocross with 10" slicks front and rear. I used a 7/8" front bar with solid aluminum blocks mounting it to the frame. I used Guldstrand springs front and rear. The rear bar was the 70 Camaro type and a pretty small one like half inch dia but it's got short arms compared to a Hotchkis rear bar so it's somewhat stiff for it's size.

When I put on the street tires and wheels it oversteered, but I had fun with it.
David
67 RS Camaro, 69 Camaro vint racer, 65 Lola T-70 Can-Am vint racer.
ourworld.compuserve.com/homepages/David_Pozzi/

Edited by: davidpozzi at: 7/9/04 8:16 pm

Ralph L
Moderator
Posts: 3634
(7/10/04 12:35 am)
Reply
Re: What are you running for a rear sway bar?
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I can try and move this info to another post, possibly tomorrow, if I get a chance, sorry for the delay.
Ralph
Project Fantom Expected Completion - May 2005
My Tahoe - "Black Mamba"
Rendering of Project Fantom

Rick Dorion
Registered User
Posts: 597
(7/10/04 4:04 am)
Reply Carl
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Carl, are you still running the Hotchkis rear bar?

CarlC
Registered User
Posts: 191
(7/10/04 12:47 pm)
Reply
Re: Carl
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I took it off. I questioned the affect this bar has since it mounts so far inboard.

I'm going to keep the bar in case I need it for tuning, but I don't see a need for that right now.

Back-to-back testing is necessary but the Hotchkis bar is not easy to remove from the car.
http:www.geocities.com/casanoc

Mean 69
Registered User
Posts: 60
(7/11/04 10:31 am)
Reply More Tech
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Some more goodies on the sta-bar topic. I saw some good bits of info, thought I'd try to tie some of it together.

You have to be careful when comparing one sta-bar to another, due to a couple of issues with the design approach. One, the link length from the center of the bar, to where it connects to the frame, or wherever, has a huge impact on the torsional rigidity of the overall system. Think about it in side view, not the vertical portion that links the arm, but rather the "longitudinal" length. The longer this length, the softer the bar will be. It is pretty sensitive too, and is a very common way to fine adjust the torsional aspect of a given bar, you just move the link attachement fore and aft.

Another very important aspect is the effective length of the bar, as viewed fro the top/rear, etc. The longer the length of the bar, the softer it will be for a given cross section.

As far as tuning for understeer/oversteer, pretty much all drivers will favor a bit of understeer relative to oversteer. With understeer, the driver will feel like he has more control, you can just try to turn the wheel more, for instance. It is a lot harder for a driver to deal with oversteer, once the booty end of the car comes around there isn't a whole lot that you can do to correct for it. I had a couple late model Mustangs, which are notorious for snap oversteer, caused by bind in the rear suspension setup, they were scary to drive until I got things sorted out and learned where the limits were.

And by the way, though I love the movie, the "loose is fast" comment from Days of Thunder doesn't imply that a loose car will make it around the track faster. There is a saying that slow in, fast out will virtually always win races. This is particularly true for front engine sedans, which are nose heavy, and where you can only fit a limited amount of tire on the car. By braking earlier for the turn, and then getting in the throttle through the turn, you transfer weight from the front of the car to the rear due to forward acceleration. This take a bit of the load off of the front tire, and makes available more opportunity for lateral grip. Driving technique has so much to do with the performance of the car-driver system. Most of us want to put as much meat on the back as possible, and you can take advantage of this by setting the car up correctly, and unloading the front through turns by using the throttle.

Mark

davidpozzi
Moderator
Posts: 1227
(7/11/04 11:48 am)
Reply
Re: More Tech
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Mean 69, some good comments as allways.

To add some tips, you can tune the sway bars by swapping out polly end link bushings for stock rubber bushings, this will soften the bar and allow you to change the handling. You can change only one, two, three, or four bushings per side to achieve the softening you want. An understeering car would benefit from this approach on the front bar links. You could also change the frame mounts to rubber but that would probably make too much of a change. The softer you go, the more the car will roll in the turns but usually the amount of softening is not great enough to be noticeable, you just want a fiew pounds less front bar rate to get the balance you need.

If the car is understeering a lot, a rear bar or stiffer rear spring is going to be required.

If you need more front bar and the end links and bushings are all polly allready, you might try mounting the bar to frame in aluminum blocks.
David
67 RS Camaro, 69 Camaro vint racer, 65 Lola T-70 Can-Am vint racer.
ourworld.compuserve.com/homepages/David_Pozzi/

Edited by: davidpozzi at: 7/11/04 5:10 pm

chicane67
Registered User
Posts: 135
(7/11/04 2:15 pm)
Reply | Edit Re: Carl
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Alright, lets start out with what has already been stated. You say the chassis has an understeer even with the amount of toe-out you have dialed in. As David briefly pointed out, this condition can be handled with rate changes either spring, bar or both.

With understeer, it can be corrected by either a rate increase in the rear spring (and/or) the addition of (and/or) an increase in rear stay bar, or on the other end of a chassis, a reduction of front spring (and/or) a reduction in front stay bar.

Your stated tire temps with the amount of toe and noted understeer tells me that you don't have enough rear roll stiffness and is pointing toward an increase in rear spring. Not to mention that you will also have better IC location from the rate increase/spring build/spring design which is a major contributor to "off corner" acceleration and exit stability.

The weight issue. The chassis needs to go on a 500 pound diet (yea, I know)........the driver, a 25 pound diet (the wifie would love that huh?)......you need to remove 44 pounds from the left front and distribute that 44 pounds across the rear, something to the tune of 18 to the LR and 26 RR. Rescale the chassis. What the object to do here is get the L/R split even and worry less about the F/R split. Cross weight and F/R split is all about weight management and its placement, but the L/R split is all about transition and that is what we need to concentrate from the beginning.

IMO, a 240 ish rear spring rate without a rear stay bar would be an easier place to start. Keep everything else the same and only tune one aspect at a time.

Spring.....shock/valving.....stay bar.

jon
Unregistered User
(7/11/04 5:29 pm)
Reply x
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has anyone tried afco leafs?they are about $110 each and have springs in some of the rates discussed.not sure of the fit,they are listed for 70-81 camaro,does anyone know if that will fit a first gen?i'm adding a 1.25 dia. tubular bar right now.it will have arms adjustable to 8.5 or 9".i'm going to start with a .125" wall bar and also ordered a .188" bar also.the bar is 40.5 long.any opinions?

streetfytr68
Registered User
Posts: 1169
(7/11/04 5:47 pm)
Reply The Magic Question
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And now: For the magic question:

Where does one get the right 240lb spring?

Most of us are building hot rods that handle. The ride height must deliver good looks and clearances as well as good handling. So given a baseline rate and arch and a new target rate, how do you establish a target arch to avoid do-overs?

www.lateral-g.net

chicane67
Registered User
Posts: 140
(7/11/04 5:48 pm)
Reply | Edit Re: x
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I believe they are good enough for a race car, but would need replacement after a season or two maybe even three and the design has definite limitations. I have seen some use the AFCO springs is limited street applications, but can only tell you that the spring steel used is imported and not of the highest quality. Not saying that they are all that bad, cuz all there stuff is real nice, but there is a difference in spring steel and the difference in cost is actually quite staggering.

The build of the leaf is just as important as the rate itself. So, just throwing a leaf spring in a chassis that meets a specific rate will only do so much......the leaf spring has to be built correctly to do more than just hold up the ass end of the car.

I dont have my 'black book' in front of me right now, but the dimensional differences between the 1st and 2nd Gen are similar, but.....do have some slight differences. I believe the differences in the center to center and pin to forward eye dimensions.

As for the bar......I'd have to scribble the math to give any kind of thought to it.



chicane67
Registered User
Posts: 141
(7/11/04 6:00 pm)
Reply | Edit Re: The Magic Question
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Quote:
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And now: For the magic question:
Where does one get the right 240lb spring?

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You sell your house and move your ass to Vegas.....and then I build you a set.

I have two spring builders in the country that can and have built my spring design to 'spec'. However, I myself will only use one of them for my personal builds. This cat is also the very same that builds the famed 'TriCity Competition' springs.....his attention to detail and knowledge is second to none.

The free arch is set to run flat when installed into the chassis and the final ride height is tuned with a 1" lowering block..... but the target arch has already been tested and works as configured. When you get out this way, we'll give you the grand tour with the 320 inchers that are currently in the 67.

streetfytr68
Registered User
Posts: 1171
(7/11/04 6:11 pm)
Reply Re: The Magic Question
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Works for me. But the wifey's gonnna be pissed. "Honey, I dropped the price on the house so'z I could get summa dem 320 lb springs"

www.lateral-g.net

Mean 69
Registered User
Posts: 61
(7/11/04 6:19 pm)
Reply Or....
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You could drop the leafs altogether, cut a little channel in the driveshaft tunnel (not too bad), and convert to a really cool three link!!!! Then, anytime you wanted to change spring rates, it would cost you less than $100, and take you minutes. And adjust the ride height. With plently of room for shock compression. And, on top of everything else, it looks really cool! Want to dial in more anti-squat? You got it. Lower the RRCH? You can do that too.

Packaging is 90% done, now all I need to do is to get Matt from RFR to make me the real brackets.....

Geez, Steevo, are you really moving to Vegas?! Oooh! You can get in trouble out there, with the likes of Tommy in town and all....... I'd give Tom's spring design a shot, the young man is wise beyond his years, no doubt. Just a question though, like Carl, I kind of assumed you were happy with your car, what doesn't it do that you want it to?

M

chicane67
Registered User
Posts: 142
(7/11/04 6:57 pm)
Reply | Edit Re: Or....or what ??
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Hey M.....

You are almost like a 'pusher' on an Oceanside street corner......."Pssssst, hey buddy.....have you ever tried a threee link......do ya wanna ??".....

Your next homie. Go public and then hook up with the Vegas punks. The four of us (Tyler, Steevo, you and myself) need to have a little pow-wow.....what is looming in the near distance may be worth some real consideration. Looks like its time for a round of e-mail.

Is everone coming to SEMA this round ??

Edited by: chicane67 at: 7/11/04 8:18 pm

davidpozzi
Moderator
Posts: 1228
(7/11/04 7:07 pm)
Reply
Re: Or....or what ??
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Tom, I've got a mental picture of you standing on a street corner, wearing an overcoat with leaf springs hanging inside!
David

67 RS Camaro, 69 Camaro vint racer, 65 Lola T-70 Can-Am vint racer.
ourworld.compuserve.com/homepages/David_Pozzi/

Edited by: davidpozzi at: 7/11/04 7:17 pm

Mean 69
Registered User
Posts: 62
(7/11/04 8:09 pm)
Reply Ha!!!!!
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Can you just imagine the picture!!!! Tom, with springies hanging out of his jacket.... Sly look on his face... You'd better start lifting weights, Tommy, those leafs are heavy!

E-mail away, I'm all ears. There are SO many people to delight with really great hardware solutions, and oh-so-many ways to do such.

M

P.S. I've seen some of those O-side folk, but I ain't never seen one with a three link!

P.S.S. Michael Shuie and team Red are just nuts, unreal domination. Just watch how calm his hands are with the steering wheel, it's just not right!!! Watching the BGP, halfway through the replay...