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Vehicle lift as a function of coil free length for 120 series Prado

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  • Vehicle lift as a function of coil free length for 120 series Prado

    Hi everyone,

    I’ve put together a couple of plots which users may find helpful, as it is a bit difficult to compare the resultant lift from different lengths of coil springs without a plot. These plots are made by using the “suspension database” and “suspension measurements 2” threads, where users have reported their vehicle lifts.





    Some points to note:

    1. Lifts reported are bottom of rim to guard measurements, all on 17” Prado rims.

    2. None of these measurements include coil or strut spacers.

    3. All front lifts are bottom circlip position unless stated otherwise.

    4. Lifts are typically reported immediately after suspension install, so do not include sag.

    I haven’t included TFR-118EHD as part of the trend-line fit for the IFS, as it is a very short coil with extremely high spring rate. Notably, large 0.5-1” lifts are achievable by moving up circlip positions on front struts, by virtue of pre-load increasing.

    When using inflatable airbags in the rear for GXL and VX models, reported lifts for the rear can reach 3.5”. It is clearly better to report your lift with airbags deflated/minimal pressure, so the lift from the coils alone can be discerned.

    Most of the reported lift measurements are for vehicles that have bullbar/winch/dual batteries in the front, and a constant loaded cargo area (drawers, fridge etc.) in the rear, which gives everyone an idea of the lift that is achievable in a typical off-road configuration.

    Some users are reporting more satisfactory results on the 120 IFS with stiffer 150 series coil springs such as C59-352 and C59-350 (725lb/in compared to 586lb/in), less nose diving under brakes with bullbars etc.

    It appears that to achieve a 2” lift (the most discussed in the forum) with close to factory spring rates, you will need >390mm coils in the front, and >400mm coils in the rear. The lift from these length coils are constrained by the spring rate, as provided in the suspension database, and the pre-load in a strut assembly. Lift in the rear can be strongly influenced by a heavily loaded vehicle (e.g. fully loaded cargo area + roof rack), so I would personally be using at least 410mm for heavy off roaders, and have airbags to combat load sag.

    I’m also quite interested to hear reports of coil sag after ‘n’ months. Having read through many different suspension threads, it seems Ridepro, Kings, Lovells and OME coils can sag quickly over time, while in contrast, some users report Dobinsons coils not sagging at all over many years. Some users report the complete opposite of this, so it’s very hard to get a consistent picture without a bunch of sag measurements. Dobinsons have been reported as being quite stiff, but note that Dobinsons make Ridepro coils, which can sag significantly.

    Are there many users who have pulled their coils out and checked the change in free length after heavy/long use?

    One other measurement to be aware of for the selection of coil free length can be seen from the following plot;



    For my current setup with BE5-A712/ZC7296, the maximum shock travel of 570mm on the front IFS in this case shows a coil working height of close to 350mm. So if you choose very short coils (such as TFR-118EHD 345mm free length) with long travel struts, you may reach the coil free height on full extension and your coil spring will be loose. On this basis, it seems sensible to stay above the OEM free length of 370mm, so the coil always remains pre-loaded.

    Best from the Bris

    Mark
    Whitey
    Shockie Maker of the Month Award
    Last edited by Whitey; 20-09-2017, 03:58 PM. Reason: Plot update
    2006 GXL petrol auto. ARB deluxe bar x3 HID IPF's, ARB alloy roofrack, ARB awning, BFG A/T, Safari snorkel, Piranha breathers, Pacemaker extractors, custom Ironman 45710FE 436-569mm with Dobinsons 350, custom Ironman 45682FE 383-618mm with Dobinsons 487, Firestone kevlar 60psi airbags, 30mm extended Roadsafe links, AMTS bashplate and recovery points, ABR Flyer with Powersonic AGM.

  • #2
    Genuine "sag" is a change in free height.
    So I hope all the reports of sag have removed & measured.

    Often peeps misuse the word sag, they mean, they added more weight & it went down more or it settled.
    Over time things get added, fuel tanks get filled, & like any spring, add weight & down she goes!
    If u take it out & it's the correct free height it's not sagged, you chose the wrong coil.

    The only time I have seen genuine sag in DOBINSONS, well it wasn't genuine really, it's when DIY use cheap dangerous bench spring compressors on the front coils & over compress them to fit into the strut. They get squashed permanently damaged. A whole new free height. Can be picked by rolling the coil & it's no longer str8 either.

    Comment


    • #3
      Hey,

      Excellent info on the DIY compressors buggering the free length, I'll be putting my struts together very carefully from now on!

      Sounds like the Dobinsons are good, but I'm certain my Ridepros (=Dobinsons) have sagged a little, as my coil working height started out at 307mm, and its less than 300 now. When I put in my new struts, I'll definitely measure the free length again and check how much sag there really is.

      Mark
      2006 GXL petrol auto. ARB deluxe bar x3 HID IPF's, ARB alloy roofrack, ARB awning, BFG A/T, Safari snorkel, Piranha breathers, Pacemaker extractors, custom Ironman 45710FE 436-569mm with Dobinsons 350, custom Ironman 45682FE 383-618mm with Dobinsons 487, Firestone kevlar 60psi airbags, 30mm extended Roadsafe links, AMTS bashplate and recovery points, ABR Flyer with Powersonic AGM.

      Comment


      • #4
        I have some Dobinsons part numbers & free heights in my head, do you have those already?

        I don't remember the load, I just know what they do, as in which one to use to get the lift my customers want.

        On a 120:

        The fronts i use all start with c59-

        296 - 378mm
        300 - 385mm
        302 - 395mm petrol full accessories 40-50mm lift
        314 - 405mm diesel full accessories 40-50mm lift.

        Rears c59-

        325 - 420mm light & comfy. A great coil, but if u have constant load or really load up when u go away u will go down a lot.
        327 - 410mm or whatever length I order popular coil. Medium & still comfy, I use this 90% on prados. Retains pretty well.
        329 - 410mm heavy, comfy if loaded a little.

        On a 150:

        Rears are the same, always used 327.

        Fronts c59-350 with steel Bullbar.
        352 with the lot. It's 5mm longer, 10mm at the wheels, can't even remember free height :-)

        Use those on front of Heavy hiluxes too.

        Comment


        • #5
          You can prime up the strut, a couple cycles in & out o get the air out, make sure its upright.
          Also make sure when you assemble, you line up the top & the bottom 99%+ it will make it easy to put the strut in. Also save leaving the bush installed on an angle/twisted.
          Don't leave the top bolt too loose, it may cause some bounce, on the other hand, there's no need to over tighten & squash the crap out of the bush.
          Leave the bottom bolt/bush finger tight till its on the floor & been bounced. Generally bushes only allow 30% twist.
          with the Prado lack of travel, it might not matter? But it's good practise. Once it's on the floor & bounced 135n/m.
          The other issue with tightening before its in its neutral position is side load & possible uneven/premature wear to shaft & seals.

          Comment


          • #6
            Hey everyone,

            Have updated the rear plot to include King KTRR-102, which is a commonly used coil for the rear.

            I also added some more C59-327 data. The variation in lift from this coil can be quite large, from around 2-3.2". Strongly load dependent.

            Best

            Mark
            2006 GXL petrol auto. ARB deluxe bar x3 HID IPF's, ARB alloy roofrack, ARB awning, BFG A/T, Safari snorkel, Piranha breathers, Pacemaker extractors, custom Ironman 45710FE 436-569mm with Dobinsons 350, custom Ironman 45682FE 383-618mm with Dobinsons 487, Firestone kevlar 60psi airbags, 30mm extended Roadsafe links, AMTS bashplate and recovery points, ABR Flyer with Powersonic AGM.

            Comment


            • #7
              Can someone share an updated link?

              Comment

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