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  1. #1
    Fellow Frogger!
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    Default spring modification

    when i bought my 12 g they came with a set of customised rear springs.
    They were made by kingssprings have the same amount of coils as normal r12 springs but a alot thicker . i installed them today and this has raised the back of the car somewhat almost 3 centimetres more than the front.
    If you cut one coil of the springs is there a risk of spring cracking or upsetting the spring rate does anyone no where the major spring compression is a 12 rear springs becuase they are very firm springs but car now sits too high in back .

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  2. #2
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    Sounds like you'd need to get them re-set - if you cut them, they'll be even stiffer. Incidentally, that spring spec sounds almost identical to my Nissan Pathfinder rears on the R12 Wagon. They're made of thicker wire, same no. of coils and raised the back about 2cm, which was actually what I wanted for loads.

    Stuey

  3. #3
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    Default springs

    stuey if i cut em though it will ower the height correct which is what i want stiffness not to bad shouldn t affect back end handlingtoo much should it shoul;dnt make it pig hop at all not sure but i want it lowerthats all
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  4. #4
    Tadpole David Mc's Avatar
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    Hey Guys think about the laws of phisics here.
    Less coils due to cutting means softer spring as there will be less metal and coils to hold up the car. Not stiffer. To make stiffer you need thicker steel or more coils.
    The real way to lower the Back end now that you have new springs is to get them re-set. As in heating them up and compressing the spring. Can be done at home but it realy needs a proper jig so that both springs will be set at the same height as each other.
    Did you ask for harder springs when you had them done or did you ask for higher rate but at the standard or lower height?
    Kings would have just made exact copies of you old srings but with thicker spring steel . So no the car wont compress the coils down enough as it used too.
    I hop this Helps.
    David Mc

  5. #5
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    Quote Originally Posted by David Mc
    Hey Guys think about the laws of phisics here.
    Less coils due to cutting means softer spring as there will be less metal and coils to hold up the car. Not stiffer. To make stiffer you need thicker steel or more coils.
    Have a re-think of the laws of physics...

    EACH COIL on a compression spring will deflect a certain amount for a given load...

    The amount of deflection PER COIL is determined by the diameter of the spring steel used on the spring, THIS CANNOT BE CHANGED and remains the constant.

    If you remove a coil link, each coil will still deflect the same amount for a given load, but as there are less links, the spring will now have less total deflection for the same load, effectively making the spring stiffer...

    As an example, let say that a coil compression spring has 10 coils of 10mm wire and has 10mm of deflection per 100kg.

    That would mean that each coil has 1mm of deflection per 100 kg totaling 10mm for the entire spring...

    If you remove 1 link the spring would then have 9mm of travel per 100kg so you have increased the spring rate by 10%...
    Last edited by mistareno; 29th August 2004 at 02:02 AM.

  6. #6
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    Quote Originally Posted by daniel the r12 nut
    when i bought my 12 g they came with a set of customised rear springs.
    Just wondering, does the car still have the original 12G spacer plate on top of the rear spring (or stuck to the body)? Removing the spacer plate may drop it to your desired level. If no spacer plate just ignore the advice....

  7. #7
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    Quote Originally Posted by David Mc
    Hey Guys think about the laws of phisics here.
    Less coils due to cutting means softer spring as there will be less metal and coils to hold up the car. Not stiffer. To make stiffer you need thicker steel or more coils.
    The real way to lower the Back end now that you have new springs is to get them re-set. As in heating them up and compressing the spring. Can be done at home but it realy needs a proper jig so that both springs will be set at the same height as each other.
    You can't even SPELL 'physics'! As Richard said, you're wrong there.

    Stuey

  8. #8
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    Default springs

    so if i lop a top coil of will it make it softer in the back or harder me thinks harder however richard you said u did it how did your car react and how u have twin sway bars on rear end set up please tell me
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  9. #9
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    Quote Originally Posted by daniel the r12 nut
    so if i lop a top coil of will it make it softer in the back or harder me thinks harder however richard you said u did it how did your car react and how u have twin sway bars on rear end set up please tell me
    If you lop of a coil, it will get stiffer...

    I like the rear to be quite stiff as it allows much better turn in, and less understeer...

    If the springs are already very stiff, I wouldn't advise going any stiffer as the car might become a bit taily if you over cook it into a corner...

    It all depends on the driving style....

    BTW - If you don't have a set of dampers capable of controling the springs it may feel softer because it is underdamped and bouncy...

  10. #10
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    Default springs

    ok shockers in rear are not too bad if i cuttop of the springs which are hard but similiar to 12wag hardness it will lower car to proper height not 2.5 cm higer at back than front how richard did u have twin rear ssway bars car doesnt pig hop now so would u think it would? or just make it twitchy on turn in
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  11. #11
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    Quote Originally Posted by daniel the r12 nut
    how richard did u have twin rear ssway bars car doesnt pig hop now so would u think it would? or just make it twitchy on turn in
    With the 12G 24.5mm rear anti roll bar I wouldn't think you would want to go much stiffer with twin anti roll bars, especially if the springs are already pretty stiff.

  12. #12
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    Quote Originally Posted by Simon
    With the 12G 24.5mm rear anti roll bar I wouldn't think you would want to go much stiffer with twin anti roll bars, especially if the springs are already pretty stiff.
    Daniel, I would agree with Simon.

    My car had 2 much thinner rear sway bars and firmer rear springs.

    If your car has a 24.5mm rear swaybar, this is huge for a 800kg sedan...

    I would probably just wait till the car is on the road before worrying about any of this stuff.

    Then drive it to get a "base point"

    For all you know the higher rear springs may be for loose surface rallies where the previous owner may have wanted a higher rear roll center to enduce roll oversteer to counter act the understeer...many drivers like different feeling cars on the dirt...

    Do you have the original springs also??

    I thought standard 12G's were always pretty tight to start with

    I personally find that firm spring rates are not as important as well matched dampers and swaybars...

  13. #13
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    Default springs

    ok guys i think we confused here the springs came with the car and and are in my white 12 sedan at the moment which has 17 sway bars from and rear it had virage sedan springs in the rear b4 but now for some competiontion use i put these springs that came with the 12g in the back of my WHITE car.
    Noww yes the 12 g has a 90 litre fuel tank in back which mayu lower bum a little buti want to no would lopping a coil of thses springs lower the height and not harden it up too much further.
    the reason i put thses springs in was to reduce the nosing up the cardoes when launching it just to try reduce it a little
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  14. #14
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    Quote Originally Posted by daniel the r12 nut
    buti want to no would lopping a coil of thses springs lower the height and not harden it up too much further.
    the reason i put thses springs in was to reduce the nosing up the cardoes when launching it just to try reduce it a little
    Well, I certainly wouldn't go lopping those springs into pieces, especially as they may have been custom made for the 12G. Once lopped forever lost.

    How about sourcing some 12 wagon springs they may give you the ride height you need. Or get the Virage springs reset to give a better ride height.

  15. #15
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    Bluey,

    I looked all this up a while back when I was thinking of getting custom made springs. I got this info then.

    There are three basic principles in spring design:
    • The heavier the wire, the stronger the spring.
    • The smaller the coil, the stronger the spring.
    • The more active coils, the less load you will have to apply in order to get it to move a certain distance.
    Based on these general principles, you now know what to do to change the properties of a spring you already have. For instance, if you want to make automotive suspension springs a little stronger than stock, you can a) go to a slightly heavier wire and keep the dimensions and coil count the same, b) decrease the diameter of the spring, keeping the wire size and coil count the same, or c) decrease the number of active coils, keeping the wire size and spring diameter the same. You can also go to a stronger material to achieve the same result.

    Given that the concept of 'stiffness' equates to the amount of deflection for a given severity of bump (or other loading), if you reduce the number of active coils by cutting them off, you'll get less deflection over a bump - or in other words the spring will be stiffer in its action.

    When I was trying to understand it, I went back to the concept of a coil spring being a coiled torsion bar. It seems to make more sense if you think of the above in terms of a straight bar. The coil size and number of coils both affect the length of the bar. If you imagine a looooong bar, it's easy to imagine that it would be easier to deflect (twist) than a stubby bar of the same diameter material.

    Cheers

    Stuey
    Last edited by Stuey; 1st September 2004 at 01:56 AM.

  16. #16
    1000+ Posts REN TIN TIN's Avatar
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    I have a little EXCEL spreadsheet that calculates spring stiffness. If anyone wants it, let me know and I'll email it.


    Ren
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure. Mark Twain"

  17. #17
    Fellow Frogger! Bluey's Avatar
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    My apologies.
    I went and found out today and yes cutting a spring does make it stiffer. Cut a spring in half and it will have twice the spring rate.

  18. #18
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    No worries Bluey. I didn't know it without looking it up a while back.

    Stuey

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