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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 7:00 am 
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Location: N.J.
shrinker wrote:
can you post some logs of when its fast and slow?



On the road right now but will do when I get home....

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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 7:03 am 
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Location: Adelaide Australia
I figure your car is very similar to ours, Similar times and weight and style But i dont know the details for your car. Could you inform me please.


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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 7:06 am 
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shrinker wrote:
I figure your car is very similar to ours, Similar times and weight and style But i dont know the details for your car. Could you inform me please.


Details??? What do you want to know???

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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 7:10 am 
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Its weight, wheelbase, power, CGH, fourlink settings etc. Just the stuff to get a general idea If you want to can email me exact dimensions and I can run it in my prog and we can see how it turns out.


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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 7:13 am 
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not sure of power never dynoed cgh???

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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 7:14 am 
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center of gravity height. It doesnt matter if you dont have all the stuff, I can fudge it. The car is a low build chassis car? So its going to be similar to other stuff like it.


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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 7:20 am 
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Check "car of the month" ?My Car

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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 7:29 am 
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This is the info i need to calculate it if you wish too. With some example numbers.

diff ratio= 4.71
rear tyre circ= 104

gear box first gear ratio = 1.76
rear spring rate 175
front spring rate at wheel 225
tyre press psi 7.65

The four link geometry measured with car sitting on ground.
chassis end attachment upper forward of axle C/L x= 19.375
chassis end upper above ground y= 13.2
chassis end lower forward of axle C/L x= 20.1125
chassis end lower above ground y= 6.75
axle end upper forward of axle C/L x= 2.75
axle end upper above ground y= 18.8
axle end lower forward of axle C/L x= 0.5
axle end lower above ground y= 7.75
scaled weight's
left rear= 543
right rear= 631
left front= 607.5
right front= 603.5
static cgh= 14
rear axle assembly weight= 328
wheelbase= 107
FRONT tyre dia= 26
rear tyre press= 7.65
front tyre press= 35
rear tyre tread width in contact with ground when static on start line 15
max tread width= 15
[code][/code]


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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 7:39 am 
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Ok will do =;



You taking notes John???

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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 8:02 am 
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Location: Western Illinois
Barry, Let me get a grasp of your spring deal. You have 110 lb 14 inch springs in the car and they are compressed to 9.5 inches to achieve ride height, and you have a 125 lb 14 inch spring that you need to compress only to 12.5 to achieve ride height? that don't add up in my mind. Is one of these not the correct length for your coil over shock? If one of these is for a shorter shock, you would be better off with a spacer instead of compressing it. If it is for a longer shock you can't cut it and get the same spring rate. Right now you are compressing in a difference of preload of 187.5 lbs of stored energy in the 125 lb spring and 495 lb of stored energy in the 110 lb spring at ride height. I don't know what your corner weight is, but you would have to get 605 lbs corner weight to get that first inch of travel on the 110lb spring, but only 312.5 to get that same inch with the 125 lb spring. this plus the fact that your coil overs are mounted behind the axle center line makes the spring stiffer at wheel rate. Maybe I'm misunderstanding this? Question? When you take the slack out with adjuster nuts, from there how much compression in inches do you have to get ride height on each spring?

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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 12:13 pm 
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OK !!!!!!Now your understanding what I am trying to say Dennis...I am not sure of how much the 110lb spring is compressed that is on my car now but what I was trying to tell you guys is the difference between the two springs of how much each one is differently compressed to get ride height........So if I change to the 125lb spring and it is only compressed, lets say 2 inches it has less stored energy than the 110 lbs spring that is compressed 5 inches..........So maybe the way my car is right now that spring (110lb)has to much energy to compress it more to keep the tires planted on the track...... 8-[ The car in the back according to my logger is in an extended position going down track till almost the very end.........yes.........no.........???

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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 5:01 pm 
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Any spring will compress the distance that its rate dictates for the weight it supports. If the load supporting distance of the shocker is way wrong between the 2 springs then the free length must be different. The car weighs the same with either spring in it at the rear so 600 LBS of weight will compress a 110LBs spring 600/110 = 5.45" and a 125LBS spring 600/125 = 4.8" If the difference in ride height between the 2 springs in different than this calculation then the free length is different between the 2 sets of springs or the rate is not what you think it is, Or the weight is not what you think it is.


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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 5:25 pm 
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shrinker wrote:
Any spring will compress the distance that its rate dictates for the weight it supports. If the load supporting distance of the shocker is way wrong between the 2 springs then the free length must be different. The car weighs the same with either spring in it at the rear so 600 LBS of weight will compress a 110LBs spring 600/110 = 5.45" and a 125LBS spring 600/125 = 4.8" If the difference in ride height between the 2 springs in different than this calculation then the free length is different between the 2 sets of springs or the rate is not what you think it is, Or the weight is not what you think it is.


That is the way I see it too. The key words are they the same length spring for that coil over. I have stepped in the middle of a deal where they had a well used 16 inch spring on a 14 inch shock. You couldn't get the adjusting nut on with out compressing the spring first. It will never give that stored energy back. It will still compress with the weight of the car as long as the weight exceeds the stored energy that was compressed in the spring to start.

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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 6:21 pm 
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Barry can you push the back of the car down? Maybe you have a frozen shock or a bound up anti roll.


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 Post subject: Re: Suspension Dynamics.
 Post Posted: Mon Apr 06, 2009 6:32 pm 
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Beretta wrote:
OK !!!!!!Now your understanding what I am trying to say Dennis...I am not sure of how much the 110lb spring is compressed that is on my car now but what I was trying to tell you guys is the difference between the two springs of how much each one is differently compressed to get ride height........So if I change to the 125lb spring and it is only compressed, lets say 2 inches it has less stored energy than the 110 lbs spring that is compressed 5 inches..........So maybe the way my car is right now that spring (110lb)has to much energy to compress it more to keep the tires planted on the track...... 8-[ The car in the back according to my logger is in an extended position going down track till almost the very end.........yes.........no.........???


As long as you don't have to put a spring compressor on the spring to just get it on the coil over, and it has good travel in compression and separation you are just storing the weight/ energy of that corner. Sure you will run the adjuster nut up farther to get ride height on the lower rated spring. Just because the distance changed it still has 600 lbs if that corner is 600 lbs. The difference is how it takes weight and gives it up. The lighter spring will take it faster and give it up slower or over a longer range of motion. Do you remember the garage spring discussion we had in here a long time ago? The heavy door spring will make the door easier to open but may not get it all the way to full open. the lighter spring will help all the way but not as much so it is slower, when you close the door the heavy spring is harder to close (takes weight slower) and light one closes easier, (takes weight faster).

If your logger shows your in separation all the way down the track and you trust it, then your IC must be a little high for your COG. Springs aren't going to do that. That takes us back to too low a COG for power. The car keeps talking. With the logger yours is bi-lingual lol.

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