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Ironman Foam Cell Pros – long travel hydraulic shocks for the Prado rear

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  • Ironman Foam Cell Pros – long travel hydraulic shocks for the Prado rear

    Hey all,

    I’ve recently been looking at finding a rear shock for the Prado that is more fade resistant, that can handle a heavily loaded rear, and which gives high droop and a decent “touring” type open length over 600mm. I’ve already killed small bore 2” twin tubes in the rear which only utilise a 35mm bore in the pressure tube. 2” twin tubes are simply not fit for purpose in a loaded Prado rear. They will fade quickly and can get so hot you cannot hold your hand on them.

    Monotubes at the same 2” outer body diameter such as Bilsteins offer a bigger 46mm bore, but surprisingly only use around 300cc of oil volume, and they can also get as hot as bbq hotplates in the rough stuff. I also think a 14mm shaft is on the small side when it comes to the heavy Prado rear in long travel geometry, as there is a lot of side loading on the shaft in the rear. I will be looking at 60mm diameter non-inverted piggyback monotubes in the future.

    Big bore pure hydraulic shocks (pure hydraulics have air above the oil) such as Koni have a great reputation for fade resistance, principally due to the fact they hold a significantly larger volume of oil (twice the volume of a 2” monotube) which can dissipate thermal energy faster. They also utilise a large 18mm diameter shaft. Koni make a rear 90 series RAID shock for the Prado, 90-5404, it is one of the largest diameter shocks you can currently put in the Prado rear. However, the 90-5404 is only 587mm open length, and is valved very softly on rebound with high compression for a soft OEM type coil rate, meaning it is not useful in lifted geometry, and it is not useful in a heavily loaded Prado which requires stiff coils. The low rebound of the 90-5404 will not be able to control the notorious pogo stick dynamics of the Prado rear, undesirable pitch, heave and body roll which can be set off by mismatched front/rear coils, or poorly valved rear shocks (the case for Koni 90-5404’s and many other rear shocks such as BE5-A713 Bilsteins). The Koni RAIDS (both front and rear) will give you limited droop at a standard 2” lift, and as such should only be considered in vehicles lifted to less than 1”, and which do not do heavy touring, ie, a heavily loaded rear. In saying this, if Koni made a decently valved open length 90 series shock, I would be trying it in the rear. I have also found the customer service from Toperformance to be less than desirable, plenty of paranoia and secrecy, so modifying a 90-5404 with their assistance was out of the question.

    Ironman and Tough Dog have filled this void in the hydraulic long travel after market, and both companies offer rear hydraulic shocks for the Prado with the same geometrical dimensions as the 90 series RAIDS. These hydraulic shocks utilise Foam Cell technology to minimise oil cavitation. Instead of air above the oil as in a pure hydraulic shock, the air is replaced with a nitrile type material (consistency like a diving wetsuit) that is impregnated with gaseous nitrogen under pressure. Nitrogen molecules enter the stringy plastic-like fibrous network of the foam cell material and create small micro sacks of nitrogen inside the fibres. As such, the foam cell can swell and contract under oil pressure changes, in much the same manner as a floating piston acts in a monotube. The nitrogen impregnated foam cell keeps pressure on the oil and prevents cavitation. So foam cell big bore hydraulic shocks are an upgrade from a pure hydraulic shock, and they can minimise cavitation, and hold more oil than a pure hydraulic. This means hydraulic foam cell shocks run cooler than pure hydraulic shocks. I’ve read and heard the anecdotes about foam cells falling to pieces, but I haven’t seen one. Even if the foam cell failed, I’d just pull it out and run the shocks as pure hydraulic long travel versions.

    The choice of manufacturer was made easy for me as I’d already spoken with the chief shock builder Kristian at Ironman a few times previously and my good mate John at Zordos is an Ironman distributor. So I bought myself a pair of 45682FE shocks. I initially opted for the 80 series spec valving, as it has higher rebound (for heavy rear body roll control) than the Prado spec valving. The figure below shows the two different valving specs;



    The plot also shows the valving for a Bilstein B46-1478S (slightly modified from its spec valving). This modified 1478 valving is very close to the valving I was already running in my small bore twin tubes. I have found the 3300N/800N type valving to work superbly off road in a heavy rear, particularly when it is matched to a high rate coil, ca. 280lb/in, and matched with a high rebound front strut. These are my own valving preferences, and may not be everyones cup of tea, but as always with valving, there is no right or wrong, and you should always trust your own seat of the pants intuition.

    So the options for me were to either decrease the 80 series 45682FE compression, or increase the Prado 45682FEC rebound. Either way I would need the assistance of Ironman to do this. Every shock manufacturing company is different to deal with, but I can say without equivocation that Ironman sets the gold standard benchmark in terms of polite and professional technical assistance. There are no secrets with Ironman, and their shock builder Kristian will enthusiastically help you with your valving projects. After 8 trial dyno runs, Kristian had developed a new valving stack for me, valving curve shown below;



    You can see that Kristian has achieved a nicely digressed rebound curve with a linear piston head, by adjusting valve shims to match. The low velocity damping has come out more critically damped than the Bilstein damping, which is a big plus for rough terrain handling. Catching sprung mass body roll in a heavily loaded rear is a critical part of the valving curve.

    The next step in the re-valving project was for Kristian to send me the new valve stacks and the disassembly spanner so I could rebuild my shocks at home. Rebuilding hydraulic shocks is something that everyone can do at home with a few basic tools, as there is no gas pressure complicating the disassembly procedure. It is quite simply a matter of pulling everything apart and putting it back together and making an oily mess in your garage.

    The photo below shows the new valve stacks;



    Once you have the Ironman disassembly tool, you can crack open the top dust seal;



    Once you have the top seal undone, you can pull out the oil seal/rod guide/pressure tube;



    Once you have the pressure tube out, you can drain it from below by pushing on the foot valve, then you can knock off the foot valve with a cold chisel, hammer off the rod guide with a deadblow and you’ll quickly have everything apart;



    After that, it’s just a matter of disassembling the foot valve and the piston head and replacing the valve shims;



    Once you re-torque the shaft nut and foot valve nut, just check the foot valve is working ok and the spring is located.

    After that it’s time to refill the pressure tube and the overflow chamber with oil, then cycle the piston head carefully with the rod guide in place to bleed the air from the system. This will take a little bit of work, as you need the shaft all the way out to get the entire shock volume full of oil, so you’ll need to top the rod guide bleed holes with oil until you get the shaft all the way up and the system free of air.

    Once you’ve done that, it’s easy to do the top works back up with the assembly tool. As you do it up, you’ll force the rod guide back into the pressure tube.

    All up it’s 2-3 hours of work pulling the shocks off the Prado and redoing the valve stacks.

    After putting the re-valved 45682’s back on my Prado, I could feel the difference on-road immediately, and they are very close to the feeling of my old shocks. I can start to feel the higher rebound at around 50-60km/h, and I can also notice it has decreased the body roll around roundabouts. Hitting a series of speedbumps at 60km/h was barely noticeable in terms of body movement, and I can notice the extra critical damping on the rear shocks. All up I’m very happy with the valving. I know these will give similar excellent performance off-road in valving terms, but the real test is their fade resistance. I’ll be testing them out on Fraser Island soon on the same tracks I cooked my 2” twin tubes on.

    The 45682’s contain around 680cc oil volume, over twice what is in a Bilstein B46-1478LT. The oil in the 45682 can handle up to around 260C before it will start to boil, but it’s very unlikely you’ll see these kinds of temperatures, even in the worst of corrugated conditions and hot Simpson Desert testing, Ironman couldn’t push them past 160C. I’m sure we’ll see excellent fade resistance from them.

    Length wise, the 45682FE shocks are 383-618mm, so I’d like to see the closed length shortened up to around 370mm in the future, and get them closer to typical Dobinson solid coil bind which occurs around 370mm open length.

    If you’re interested in trying some big bore Ironman hydraulics, give Kristian at Ironmans Melbourne headquarters a call. I can’t emphasise strongly enough how open, helpful and knowledgeable Kristian is, he is a breath of fresh air in a suspension industry full of paranoia about valving!

    Enjoy your big bore long travel hydraulics!

    Best

    Mark
    Whitey
    Shockie Maker of the Month Award
    Last edited by Whitey; 20-09-2017, 07:05 PM.
    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
    Hi Mark,

    Great information as always. I'm in the market for new suspension so will be very interested to hear how they go on Fraser.

    Comment


    • #3
      How about the 45683FE? They appear to be 615mm max and 370mm min?
      2008 D4D M6 GXL [MT ATZ-P3][Whitey's Ironman 45710FE/45682FE+KTFR101H/Dob487][extended Roadsafe links][Polyairs][DBA T3/T2][amts diffdrop & recovery points][Tin175's stone guards][Bushskins BashPlate][ARB Sahara][IPF 900s][Snorkel][WindCheetah][MaxTrax][IC-440][Parrot Asteroid][ARB Fridge][Lifestyle 2nd Row Fridge Mount][ARB Compressor][Thumper][SandGrabbers][Cargo Barrier][Tigerz Awning][MCC Rear Bar]

      Comment


      • #4
        Originally posted by photoprado View Post
        How about the 45683FE? They appear to be 615mm max and 370mm min?
        Hey,

        Good lengths, but they are 80/105 series solid axle fronts pin-pin.

        My old twin tube 80 series rears from Driveline services were 365-618mm, so it is possible to reach a decent closed length with twin tube geometry!

        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


        • #5
          Can't swap a pin for a loop?
          2008 D4D M6 GXL [MT ATZ-P3][Whitey's Ironman 45710FE/45682FE+KTFR101H/Dob487][extended Roadsafe links][Polyairs][DBA T3/T2][amts diffdrop & recovery points][Tin175's stone guards][Bushskins BashPlate][ARB Sahara][IPF 900s][Snorkel][WindCheetah][MaxTrax][IC-440][Parrot Asteroid][ARB Fridge][Lifestyle 2nd Row Fridge Mount][ARB Compressor][Thumper][SandGrabbers][Cargo Barrier][Tigerz Awning][MCC Rear Bar]

          Comment


          • #6
            Originally posted by photoprado View Post
            Can't swap a pin for a loop?
            Hey,

            You can, but the lengths will change as a typical EB2 ringeye is 45mm diameter, meaning the length increases by 22.5mm on one end.

            To get the closed length down on a normal ring-pin rear shock means changing shock body length, shaft length, and piston head and foot valve dimensions. Not an easy job!

            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
              Nice work!

              Comment


              • #8
                Hey all,

                I've had the chance to test my rear Ironman Pros out on Fraser Island. I was up there recently in extremely hot conditions, 45C in the shade and 60C sand temps. I did some hard driving testing out to Platypus Bay and back on the northern track which takes you to the top of Wathumba. I'd already driven up the the eastern beach to get to this track, so the shocks were already warm. The Ironmans passed the test easily, and didn't ever get more than around 10C warmer than my D563's up the front, typically around 50-60C at most.

                I couldn't get them to fade at all under these very hot conditions, so I'm very happy with them!

                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

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