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Author Topic:   Rear Suspension Question from a Dummy.
PEDDLER
Member
posted May 28, 2001 06:55 PM
From what I have read. a fifth coil spring on a slider needs to have a 1/4 in of preload. Why would the chassis builder say that the spring have a 1/2 in. of slack before contact and in reality the shock does all the work.
This car has a Z-link rear and a right brake only floated. 300 lb. rt spring and a 250lb left spring. Panhard bar (27 in) mounted on left frame with a 1 degree down hill angle to the rear end.


rockit
Member
posted May 28, 2001 09:43 PM
i thank that what he is looking for is do you preload the 5th coil or not?


Roadhzrd
Member
posted May 28, 2001 11:24 PM
my guess would be he wants more movement of the rearend. I know some people loosen their fifth coil up when it get slick and some tighten it, some will go to a stiffer spring and some go softer. Try it both ways you may not notice a big difference so whatever works for you go with it.


PEDDLER
Member
posted May 29, 2001 06:14 PM
That is somewhat the answer I was looking for. Some correction to my earlier post, a rr 250 lb and a LR 200lb spring. The car is tight in and loose off. Will reducing the preload on the fifth coil increase foward bite?
Every driver has a different style of driving. Just because a builder tells you jump off a mountain will you do it? My Question is WHY. What will be the difference? What would we see in how the car reacts.
I for one have ran stock cars for most of my racing career and have not had the opportunity to work with the different types of supension available today.I have always liked to know what something will do before trying it. It a heckava lot eaiser to know ahead of time than parking the car sideways in front of 23 others in turn 1, lap 1.
Thanks for any answers
Jim


race8k
Member
posted May 30, 2001 05:39 PM
Find out why the car is tight going in .If you fix the entry the exit may be ok.You may be shaking the car loose in the middle to get it to turn this will cause loose off.


PEDDLER
Member
posted May 31, 2001 08:21 PM
I found out that the car was not tight going in and was working exactly as the suspension was designed to do thanks to an eariler post that I went back and reread.
Other than letting the rear end rotate a little further, the question still is asked, Why leave the fifth coil loose and not preload??????
Don't get me wrong, I really appreciate the answers and I am tring to learn the way this type of suspension works.

Thanks again
The Peddler.


awkwardjeff
Member
posted June 01, 2001 03:03 PM
Peddler, HELP me out.......you stated, Z-link, lift bar.......the ONLY thing pre-load on the lift bar spring does is set pinion angle......unless you have a sixth link.
Or did I miss something?........or unless you are hard against the stop chain?


PEDDLER
Member
posted June 01, 2001 06:11 PM
Jeff: I didn't state my question well. The car has a Z-link rear with a fifth coil mounted with a coil-over eliminator and shock on a ladder style lift bar and a chain stop.The fifth coil preload or lack of is what I'm asking about.I've read Afco's artical which says to preload 1/4 in. The chassis builder say to leave loose and let the shock (Afco 9-7) do the work. If thats the case, why have a fifth coil at all?

I just plain don't understand. Please refer me to something or someone who will explain.

Thanks a lot
Jim


awkwardjeff
Member
posted June 01, 2001 11:59 PM
Peddler, I have the same suspension under one of my mods..........if you load the 5th coil while sitting on the scales you will see you are picking up rear weight.....most people will tell you NO>>>>>>but unless you put the car on the scale while doing this don't challange me.........anyway, when you are preloading the 5th coil you are adding spring weight to the rear suspension.....it's that simple. at static ride height.....now, if you move the suspension up and down it move free without any preload on the 5th........if you load the 5th and move the rear of the car up and down you will notice a differance.....this preload issue also comes into play when getting out of the throttle......I don't like any free play myself, I don't like the 5th coil slapping around in the eliminator .
If the driver is doing his job and running the car with both feet the free play of the 5th coil never comes into play......


PEDDLER
Member
posted June 02, 2001 07:23 AM
Jeff ...Thanks very much. As always you have been a very big help.

Jim
The Peddler


awkwardjeff
Member
posted June 02, 2001 07:47 AM
Peddler, I would guess your chassis builder told you to take the preload out AFTER you told him the car was tight going in and loose comming out............he was giving you a quick way to change the car and see if the 5th coild is causing the problem.
I would try HIS idea in hot laps if the track is fast and NOT slimey........
I personally would try a few other thing to get the car to turn into the corner first. skip the right rear wheel out, tuck the right front wheel in........take some cross weight out..........softer right front spring.....things like this.
there is a formula in the AFCO book telling you how to figure out whaat spring to put into the lift bar........If you need it let me know, It may take me a few hours to find mine, and then my wife will be mad because I will need to make a mess out of her house to find the catalog.......
tell me if the chassis builder told you to run 1/2 inch of free play when he sold you the car, or if this is his answer to your problem.
Jeff


awkwardjeff
Member
posted June 03, 2001 07:38 PM
Peddler, I see you are browsing the board, I clicked on live chat.........click on the same and we can chat about the rear suspension.........I'll be here a few more minutes.......Jeff


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