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  1. #1
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    Nov 2016
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    Shocks springs IRSension

    Hi there,

    i have researched old posts but cant quite find the answer,
    when the old DAX company sold me some parts in 2016 the anti roll front bar was wrong, but now overcome. But it lead me to check over all the suspension dax supplied parts.

    Car is 2002/3 IRS chassis with the extra bracing etc. Also it has the ‘lower’ spring bases at the front, thats the cradle looking piece that bolts onto the lower wishbone, the year 2000 build manual shows a flatter earlier type.
    i believe that the revised piece was to allow for a longer coil spring perhaps from an 8 inch to what i have GAZ 9 inch. Thats all well and good everything fits no problem, until my suspension guru brother in law advised that there is too much PRELOAD on the spring ie about 15mm when fully open full droop or ie not even bolted to car, i had to use spring compressors to get them on. Is it not correct that the springs should be installed without compressors with the slightest of preload just off chatter. Too much preload to start means i have lost the poundage ratings straight away no?


    The Gaz 22 click shocks (gold in colour) are new from 2016 marked as DJ02 with 13” open length measured centre of eyes.
    Should i not have longer travel shocks???? Or shorter springs? Or what?

    sure there IRS chassis guys been down this road, i would be gretful for input as always. I think i have stuff spot on but its not always the case.

    graham

  2. #2
    Join Date
    May 2016
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    Preload doesn't change the spring rating. It just changes the amount of weight that you can put on the spring before it starts to compress. Not saying that having to use compressors to get the spring off is right ( I just had to use them on my rears and I think that's wrong based on my calculations) but it's not necessarily wrong.

  3. #3
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    Just to add to my rather brief post:

    Assuming that your unsprung open/closed shock dimensions are correct for full droop and full compression of your suspension (taking into account any bump stop) and the spring rating is appropriate for the sprung corner weight and driving style (comfort vs performance), taking into account the length from the pivot to the bottom shock mount vs the pivot to the hub carrier knuckle, then preload allows you to adjust where in the available shock stroke the suspension sits while the car is at rest (e.g. 50%).

    So your situation depends on whether, when the car is on its wheels, you observe the travel being circa 50%..

    By the way, ride height shouldn't be adjusted via preload.

  4. #4
    Join Date
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    Graham,

    It's usual in my experience to have a bit of a fight to get the springs collars back into the coil over shocks. Normally spring compressors are not needed as it 'just' a matter of squeezing the springs down several millimetres to get them fitted.
    The spring poundage should matched to the weight of your car. The type of engine you have fitted will determine the lbs/inch for the front springs. This is normally 350lbs for a light RV8 up to 600+lbs for larger cast iron block engines. Rear spring rates are fairly standard (200-225 I think)
    You wind up the lower collars on the shocks, compressing the springs to get the ride height you want. 15mm sounds about right to me. There will still be a reasonable gap between each spring coil to lessen the chances of them crashing into each other under compression. If you want to set the pre-load precisely then you need to get hold of some corner weight scales to measure that each wheel is exerting the same pressure on the road.

    Russ.
    Joint Area Rep - East Midlands Region
    1984 DAX Cobra
    Rover 3.5 V8 with Holley carburetor.

  5. #5
    Join Date
    Nov 2016
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    Quote Originally Posted by Russ-Notts View Post
    Graham,

    It's usual in my experience to have a bit of a fight to get the springs collars back into the coil over shocks. Normally spring compressors are not needed as it 'just' a matter of squeezing the springs down several millimetres to get them fitted.
    The spring poundage should matched to the weight of your car. The type of engine you have fitted will determine the lbs/inch for the front springs. This is normally 350lbs for a light RV8 up to 600+lbs for larger cast iron block engines. Rear spring rates are fairly standard (200-225 I think)
    You wind up the lower collars on the shocks, compressing the springs to get the ride height you want. 15mm sounds about right to me. There will still be a reasonable gap between each spring coil to lessen the chances of them crashing into each other under compression. If you want to set the pre-load precisely then you need to get hold of some corner weight scales to measure that each wheel is exerting the same pressure on the road.

    Russ.


    ok great all good info,my springs are 375lb as quoted at the time Ford 289SBF

  6. #6
    Join Date
    Apr 2004
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    East Leake, Nottinghamshire, England.
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    From other threads on the subject Dax springs are normally too long for the spring collars to just push on but I guess if this is how they are designed there are enough well handling Dax's out there for this to be causing any problems. Other manufacturers don't have this issue but as a non expert who is to say if either way is wrong ? ?

  7. #7
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    Yup i understand everyone has same. Guess just set it up best as possible corner weighting too.

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