4 link/shock setting???

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bracketracer
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4 link/shock setting???

#1 Post by bracketracer » Mon Jul 20, 2009 5:20 am

Question is I have an IC of 51" with 89% anti squat and short time repeat within
.004 but I have my shock setting all the way tight on the extension and 3 clicks on the compression..

Possibly need a stiffer spring????? Also car started to bounce some after the stripe. Going 8.50s at 157 mph :scratch:

want-a-be
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Location: Southern Illinois

Re: 4 link/shock setting???

#2 Post by want-a-be » Mon Jul 20, 2009 6:43 pm

Enigine size, it's estimated HP and the RPM it made it at, wheel base and the weight of the car please. Rear %atge aslo if you have it. Rear spring rate? Slick size? 60' times? Launch RPMs? Stall?

This ought to get things started.

Don

bracketracer
Posts: 329
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Location: New Jersey

Re: 4 link/shock setting???

#3 Post by bracketracer » Tue Jul 21, 2009 5:55 am

want-a-be wrote:Enigine size, it's estimated HP and the RPM it made it at, wheel base and the weight of the car please. Rear %atge aslo if you have it. Rear spring rate? Slick size? 60' times? Launch RPMs? Stall?

This ought to get things started.

Don

Never Dynoed but slide ruler says 700+hp..474ci...wheel base 110 and 2400lbs with me in it rear spring rate 110,,,tire 16x33x15,,,,60' 1.16,,,,launch rpm 4800,,,,stall not positive new converter but 5800...rear weight 1060

want-a-be
Posts: 189
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Location: Southern Illinois

Re: 4 link/shock setting???

#4 Post by want-a-be » Tue Jul 21, 2009 5:47 pm

I think your shocks are too tight. When this happens, your tires end up being the shocks which will upset the way the way the tires are hooking. Rear spring is what I would be running. Loosen the extension setting of your shocks up to a middle of the road setting. Start from there. Other then the movement on the top end whats the problem again?

Don

bracketracer
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Location: New Jersey

Re: 4 link/shock setting???

#5 Post by bracketracer » Wed Jul 22, 2009 12:07 pm

My short times are the best and constant at the shock settings I listed above..This was my point extension is at it's max setting (tight).....

So what I was thinking :scratch: is if I go to a stiffer spring in theory I should have to back off (loosen) the extension up to possibly get the same results or better :scratch: .....

As far as the bouncing I am also thinking that the shock is possibly totally compressed at the end of the 1/4 causing a "no suspension" at all and it's bouncing off the tire when I lift....

This is all in what Im feeling in the seat ;)

ky mustang
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Location: Benton, KY

Re: 4 link/shock setting???

#6 Post by ky mustang » Fri Jul 24, 2009 8:27 am

Are your tires getting into the tubs when you lift plenty of clearance ? How high is your ic ?

bracketracer
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Re: 4 link/shock setting???

#7 Post by bracketracer » Fri Jul 24, 2009 11:07 am

ky mustang wrote:Are your tires getting into the tubs when you lift plenty of clearance ? How high is your ic ?

No nothing rubbing inside if that what your talking about....Right now it at 51" and 6" off the ground :scratch:

ky mustang
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Re: 4 link/shock setting???

#8 Post by ky mustang » Fri Jul 24, 2009 2:16 pm

The only time mine has bounced in the shut down was when my compression was on the stiff side. I guess it could do the same if the extension was to tight too ?

I would say if you are having to run your extension on full tight and your compression is on 3 clicks from full loose you have to aggressive of an ic for your car or the tire pressure is too low and the hard extension and soft compression setting is "band aiding" it off the line and causing problems when you lift at high speeds.

I would think the tightest extension setting would hinder the 4 links ability to separate from the chassis on a bumpy track just like a tight compression setting would keep it from coming together causing the same effect just in an opposite manner. Also the car will naturally nose dive in the shut down and want to separate in the rear.

bracketracer
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Re: 4 link/shock setting???

#9 Post by bracketracer » Sat Jul 25, 2009 8:05 am

So your suggestion is to lengthen the IC and try to keep it about the same height??? My lower bar is pointing down already so if I rase the top bar in the front bracket it should lower the IC also. This will also give me a lower % of anti-squat..right?? So by doing this it will reduce the hit and I should be able to loosen the extension on the shock.........Right :scratch: :scratch:

ky mustang
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Re: 4 link/shock setting???

#10 Post by ky mustang » Sat Jul 25, 2009 10:47 am

bracketracer wrote:So your suggestion is to lengthen the IC and try to keep it about the same height??? My lower bar is pointing down already so if I rase the top bar in the front bracket it should lower the IC also. This will also give me a lower % of anti-squat..right?? So by doing this it will reduce the hit and I should be able to loosen the extension on the shock.........Right :scratch: :scratch:
In my opinion a 4 link should be set where you can run the shocks in the middle settings on extension and compression , maybe not exact to each other but close.

How many degrees down is your bottom bar pointing down in the front ? What is the bar spread at the rear . How far away is each bar from the center of the housing in the rear ?

I do think the spread on the bars at the housing has an effect on hit. The first reaction of the car will be to separate, how much is dictated by the 4 link setting. I think you can get to worried about having a certain % of a/s because you read so much about it. I am not saying it is not important just use it as a reference point for each move you make. Make the move based on what you have learned from your previous setting and don't worry about keeping the a/s, or ic height the same because you want to change things when you move the bars.

In my opinion there is no one that can tell you exactly what your car wants , just point you in the right direction. You get close and test to find what the car wants. Video helps also , you can slow it down on a computer and see what is happening.

I will help you all I can based on what I have learned from messing with mine , not meaning to sound technical or anything because I am not an expert on them . I know how it is talking with people about 4 links . They (4 links) can be frustrating and sometimes after discussing my issues with other people I was more confused :smt003

bracketracer
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Re: 4 link/shock setting???

#11 Post by bracketracer » Sat Jul 25, 2009 1:37 pm

My lower bar is 2* down, the bar spread is 12",,, the center of the upper bar is 4 1/2" to the center of the housing tube,, and the center of the lower bar is 7 3/4" to the center of the housing.... Now I can move the upper bar 1" closer to the axle tube and can move the lower bar 3" closer to the tube...thanks for your time Mr Mustang :thumb: Your help is appreciated...

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BillyShope
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Re: 4 link/shock setting???

#12 Post by BillyShope » Sun Jul 26, 2009 6:02 am

Remember: The closer you get to 100% antisquat, the less significant are shocks and springs. And, at 100% antisquat, the shocks and springs are just going along for the ride. All weight transfer is being carried through the links and there is no relative motion between rear axle assembly and the rest of the car.

Your IC location indicates antisquat less than 100%, so you certainly wouldn't want to put it further out at the same height. Page 13 of my site has a spreadsheet for determination of IC location AND percent antisquat.

Page 38 has a spreadsheet where you can play around with spread and see its effect. You might be surprised to see that spread has no effect if the IC remains in the same location. That is, the car "sees" the same force regardless of spread. Spread does, however, have an effect on link loads.
http://www.racetec.cc/shope

bracketracer
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Re: 4 link/shock setting???

#13 Post by bracketracer » Sun Jul 26, 2009 7:56 am

Here we go again :scratch: :scratch: ........Billy the longer I make the IC the less the % of anti-squat will be...The lower bar needs to be pointing down so there is no way to get a longer IC and get it to 100% anti-squat....

A pro-mod car has IC as long as 100" long and that is in front of the car so tell me how they car get to 100% or even close to it :scratch: ...

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BillyShope
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Re: 4 link/shock setting???

#14 Post by BillyShope » Sun Jul 26, 2009 3:55 pm

bracketracer wrote:Here we go again :scratch: :scratch: ........Billy the longer I make the IC the less the % of anti-squat will be...The lower bar needs to be pointing down so there is no way to get a longer IC and get it to 100% anti-squat....

A pro-mod car has IC as long as 100" long and that is in front of the car so tell me how they car get to 100% or even close to it :scratch: ...
The 100% antisquat line, when considered in a side view of the car, passes through the rear tire patch at an angle with a tangent equal to the center of gravity height divided by the wheelbase. If the instant center is located anywhere on that line, you have 100% antisquat.

There is no requirement that the lower bar be pointed down. The important matter is the location of the instant center, NOT the angles of the individual links or their spread. In other words, pick a point on the 100% antisquat line and then point the upper and lower links at that point. Of course, the spreadsheet on Page 13 doesn't allow you to do that, so you'll have to play around (on the spreadsheet) with the available adjustment holes until you get your 100% setup.
http://www.racetec.cc/shope

bracketracer
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Re: 4 link/shock setting???

#15 Post by bracketracer » Sun Jul 26, 2009 9:20 pm

Billy, I have never seen a lower bar on a 4-link pointing up :smt003 ...Never ever!!!!!!!!! that just won't work.....You need to get to the track sometime and look around.........


KY mustang.......want a be.............HELP :scratch: :scratch:

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