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Why the Bilstein BE5-A713 should not be used in lifted Prados

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  • Why the Bilstein BE5-A713 should not be used in lifted Prados

    Hey all,

    It’s always a bit frustrating to hear suspension sales staff suggest the BE5-A713 shock for the rear of a lifted Prado, so I thought it would be informative for everyone to know why it should not be used.

    The first reason is quite simple, the A713 has a very short open length of 580mm (574mm on OEM shock), and will result in minimal droop for the standard 2” lift. With the Prado having IFS, maximising articulation on the rear is crucial for off-road performance. Maximising rear droop is critical. The plot below shows the how the rear shock open length affects your rear droop;



    The A713 has closed-open lengths of 368-580mm. As you can see in the plot, for a typical 2” lift, you’ll end up with around 60mm of droop in the rear by using this shock.

    The second reason is a little more complex, and is to do with the valving. Historically the predecessor of the BE5-A713 is the BE5-A481. The BE5-A481 was developed by Bilstein Germany for stock non-lifted Prados on soft OEM coils. The A481 was extended by 19mm (as OEM ride heights in Japan can be lower by up to 25mm) and sold in Australia as the A713 with the same valving as the A481. Most OEM Prado rear shocks have lost gas by now, but we can compare the A713 valving with a new OEM rear shock from an FJ Cruiser, shown below;



    Toyota has designed a rear OEM shock for FJ/Prado with 1700N:1475N at 0.52m/s, and they have matched this with a 195lb/in coil. Comparing the valving curves of the A713 and the FJ OEM shock shows they are very similar in magnitude and shape. The A713 has moderately stronger valving at low-mid velocity, but at high velocity, for all intensive purposes, the OEM FJ Cruiser shock behaves just like an A713 Bilstein.

    There is a higher rebound version of the A713, the 24-238830, 370-587mm with 2800N/1570N, which utilises the same compression stack as the A713. This shock would be suitable for an OEM non-lifted vehicle with a packed up cargo area. Unfortunately this is where the development of rear Bilstein shocks for the Prado stopped. Luckily for us, the problem was sorted much earlier on the 80 series Landcruiser.

    When the 80 series Landcruiser came out, Bilstein developed a similar rear shock, which was the B46-1478 (note no S or LT in the part code). This original 1478 shock had valving similar to the A713/A481. This 1478 shock was also made for a Japanese model 80 series Landcruiser which sits 25mm lower than the Oz spec Landcruiser, so it also had a very short open length.

    When the Australian model 80 series was released, fortunately for us the original 1478 was deemed to be inappropriate both in length and valving terms. This motivated the development of the B46-1478S.

    The plot below compares A713 valving with 1478S valving;



    As you can see, the valving for the 1478S for the 80 series rear is substantially different, with compression lowered by around 780N, and rebound increased by around 1560N. The knee in the rebound curve was also designed to inflect underneath 200mm/s to catch the body roll of the 80 Cruiser.

    So how does the 1478S valving connect to the Prado?

    Everyone is aware that 80 series shocks fit the back of the Prado. The rear solid-axle geometry of the 80 series is also very similar to the Prado. So length wise the 80 series shocks are a great fit for the Prado rear.

    On the valving side, I’ll use the example of a heavily loaded Prado. Many of you are aware that once you pack up the rear cargo area of a Prado the vehicle weight can quickly exceed GVM at 2850kg. I’ve seen Prados with 3200-3300kg bridge weight. For a 3200kg Prado, you are going to be running at least a 280lb/in coil in the rear to combat the sag. The calculations to get the valving needed are simple scaling from the OEM valving and coil rates;

    Rebound: 280lb/in coil needs (280/195)x(3200/2110) = 3811N

    Compression: 280lb/in coil needs (195/280)x(2110/3200) = 712N

    So a 3200kg Prado with 280lb/in rear coils will need a rear shock with valving of 3811N/712N.

    These scaling calculations are quite simple, and you can do them off vehicle weight, axle weight, sprung weight and unsprung weight. You’ll end up with numbers that are in the range 3800-4800N for rebound, and 560-710N for compression. Up to 5000N rebound will feel very stiff when the Prado is unloaded, and you could easily bounce the rear over speed bumps with that much rebound. 14mm shafts on the 46 series Bilsteins are also at their performance limits around 4000N of Force, you won't normally see more than 4000N of valving with 46mm piston/14mm shaft. Similarly, high compression can feel very twitchy on the road, and you’ll feel every little bump and it can feel like you have leaf springs in the back of your Prado.

    The most common solid-axle valving used in US model Toyotas is 255/70, or 2550N/700N, for leaf sprung vehicles. Here in Australia we tend to use more rebound for our heavier vehicles, eg, the Hilux B46-1036LT has 3200N/700N. For coil sprung solid axles, including the front of Jeeps etc., you can see valving range up to 400/100, or 4000N/1000N.

    The longest Bilstein for the rear of the 80 series is the B46-1478LT, 380-625mm, with 4000N/900N. The 1478S is shorter and softer with 380-595mm and 3865N/540N. There is also Quadrants commonly used rear shock 24-217897 which is 380-610mm with 3700N/515N.

    The rear of the Prado is very similar to the 80 series Landcruiser in terms of geometry and kerb weight (2110kg compared to 2163kg), so it is no surprise that the 80 series valving works well in our Prados.

    I have excellent feedback on the use of the 24-217897 and the B46-1478LT in the rear of both Prados and FJ Cruisers. I have received feedback that the 1478LT can feel “stiffish” on-road when the vehicle is unloaded.

    I myself have run 80 series shocks with 365-618mm and valving of 3000N/600N, and have run them at 3000kg bridge weight. The rear suspension cycles beautifully with this valving.

    My seat of the pants feeling with rear valving suggests a limit of 3500N:800N. Certainly anything over 1000N compression is going to feel bumpy when the 4wd is unloaded. The old 82 series Koni for 80 series Landcruisers is 2300N/1050N, built for OEM configuration. Koni can have quite unusual valving when compared to a Bilstein, and in this case 2300N will be nowhere near enough rebound in a heavily loaded vehicle.

    As I mentioned in another thread, I have driven on the A712/A713 combination through the Simpson in a lifted and heavily loaded 120 Prado, and the A713 could never control the 270lb/in Ridepro coil I had at the time, and the rear was very unbalanced and would force significant uncontrolled vehicle pitch which needed to be cycled out. There is simply not enough rebound in the A713 to control a high rate coil or to handle a heavily loaded rear which can run to 1800kg, which means using the brakes to slow the Prado down and kill the uncontrolled pitch, even at a miserly 20km/h.

    The A713 should be thought of as useful only for an unloaded non-lifted OEM vehicle on soft OEM springs. The short open length of the A713 also means it is not at all useful in a lifted geometry, and you will end up with only 50-60mm of droop at a 2” lift.

    As is usual for the majority of Prado owners who modify their suspension, they lift the vehicle typically at least 2”. If any sales person suggests to you to use a A713 in the rear, my advice is to hang up the phone and find somebody competent. Go for the 24-217897 or the B46-1478LT.

    Note that for 120 owners, you can get away with not lengthening your brake lines or swaybar links with the 24-217897, but you’ll need to lengthen both with the 1478LT. FJ and 150 owners should only need to lengthen their swaybar links with the 1478LT as the FJ and 150 come with longer OEM rear brake lines.

    Hope you all get your rear shocks sorted and end up with appropriate valving, and make sure to keep the open length longer than 600mm to get some decent droop in the rear.

    Best

    Mark
    Whitey
    Shockie Maker of the Month Award
    Last edited by Whitey; 20-09-2017, 05:04 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
    Great post Mark, i love reading your suspension threads as they tend to piece together all the tid bits of info I have picked up over the years about suspension in general. I'm loving my Bilstein/Dobinson setup so far.

    Cheers
    Brad
    2016 [B][I][COLOR="#696969"]GRAPHITE[/COLOR][/I][/B] GXL TD 2.8, ARB Deluxe Winch Bar, 285/65/18, Outback Solutions Drawers, Safari Snorkel, Hayman Reese HD Towbar, Firestone Coilrite Airbags, Bilstein & Dobinson lift, AMTS rear wheel spacer, Redarc Tow Pro Elite, Rhino Pioneer Platform (2128x1236mm) with more to come.

    Comment


    • #3
      Great work Mark.

      Can attest to 1000 N compression valving being pretty firm/skittish with a 280 N coil when the FJ is completely unloaded, which is somewhat mitigated going to heavier rims and bigger tyres. Would like to try a 3500/800 N Bilstein. Are you planning on offering "custom Whitey valved Bilsteins" for the rear of the Prado any time soon?

      Comment


      • #4
        Dear drwormy,

        I'm working on it!

        Valving wise I think 3500N/800N is close to ideal in a Prado or FJ, and they will drive nicely on and off road, unloaded and loaded. 280lb/in coils are what I'm running in the rear, and I think they give the best compromise in unloaded on-road comfort and off road heavily loaded. I do run airbags as well. A 280lb/in linear coil is right on the design limit at 430mm free height, and matches well the 625-630mm open length based on coil bucket separation. As you can see from the scaling calcs above, 280lb/in also matches well with 3500N/800N type valving.

        Regarding the rear shock length, it is geometrically possible to achieve closed-open lengths of 360-630mm in a short body 1478 which has the floating piston and gas chamber removed to a piggyback reservoir.

        This kind of shock is not unusual, see here;



        That is a TRD PRO piggyback on the rear of a Tundra.

        This is the design concept I'm working around. With 360mm closed, there's not much room at the bottom of the shock body, so creating the shock body/reservoir connection is the biggest design hurdle. You can buy 7100 series reservoirs straight from Bilstein USA, so I may use these and knock together a customised bottom mount for them.

        My aim here is twofold, to create a rear shock that is i) bump proof, meaning less than 370mm closed (typical Dobinson coil solid height in the rear), and ii) fade resistant. I will start with 46mm pistons and get proof of concept working, and then work my way up to bigger heads.

        Getting point i) done is just a matter of machining and being careful with lengths.

        Point ii) is harder to satisfy.

        All shocks will fade, no matter how hard you try to design your way around this problem. Shocks are a simple energy in/energy out device. When the energy in exceeds the energy out, the shocks will get hot, and I mean super hot!

        There are many anecdotal stories around about which shocks are the most fade proof in the toughest of conditions, eg., the heavily corrugated sections of the Gunbarrel Highway, Canning etc.

        I've heard the stories about laser thermometer tests on 90 series hydraulic Konis running the coolest. However, the outside wall temperature on a twin-tube Koni will not be as high as the outside wall temperature on a monotube. Never the less, it has prompted me to investigate, and I am getting some Ironman Foamcell Pros custom valved to my settings so I can run them and try a large bore hydraulic myself. Ironman Foamcells are almost geometrically identical to a 90 series Koni RAID, and the principle behind them is they contain a larger volume of oil, so more stored thermal energy can be transmitted out via the oil. The Ironman shocks are also decent lengths 383-618mm, the Koni 90-5404 for the Prado rear is useless in lifted geometry with only 587mm open length.

        Koni RAIDS are pure hydraulic, and contain only air above the oil. Ironman Foamcell Pros replace that air with the Foamcell, which is a nitrile type material containing nitrogen stored in cells inside the foam. In this fashion, the foamcell acts in the same manner as a gas chamber in a monotube, and keeps an overpressure on the oil to stop it boiling and cavitating. When cavitation starts, fade begins. ...and yes I've heard all the stories about how foamcells fall to pieces etc., but again, these are anecdotes rather than hard facts. Have you seen a torn up foamcell inside a shock, I haven't. Even if it did tear up, I would just pull it out and run the Ironman Pro as a pure hydraulic....just like a Koni.

        I am testing the Ironman Foamcell Pros on the basis of their extra oil volume capacity, if the foamcell works as advertised, then great, it's a bonus! The shock oil used in Foamcell Pros has been run as hot as 220C on the outside wall temperature, so inside would have been much hotter. Shock oils are quite hardy when there is a lot of oil in the shock. Koni 90 RAIDS have also had massive kilometres put on them, up to 300,000km on the worst stuff in Australia, just go and ask Mick Hutton about his Land Rover tours in the outback.

        Ultimately I don't believe a large bore twin tube will run as cool as a large bore monotube.

        Bilstein have 60mm bore monotubes, we just haven't seen them here in Oz yet. The 6112 series has been out for a while in the USA. There will be 60mm Bilsteins released in Australia eventually, possibly by 2018. We're up against the wall waiting for these, as Bilstein Germany is running behind on everything, they run 24/7, and cannot keep up.

        Eventually I aim to have a 60mm piggyback version of my 360-630mm rear shock.

        If it works, I'll submit a technical drawing to Bilstein and they can do a production run on them, because I reckon they'll sell like hotcakes!

        It's a long road from here to a 60mm working shock, and I am just fiddling with stuff by myself in my garage at home, but I think that a decent rear fade resistant (not fade proof) shock that is also bump proof will serve the Prado and FJ community well here in Oz.

        Best

        Mark
        Whitey
        Shockie Maker of the Month Award
        Last edited by Whitey; 20-09-2017, 05:08 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.

        Comment


        • #5
          I know I'd definitely pay for a 60mm long travel versions of the Bilsteins I run now.

          Comment


          • #6
            Originally posted by RBJET View Post
            I know I'd definitely pay for a 60mm long travel versions of the Bilsteins I run now.
            X2
            2016 [B][I][COLOR="#696969"]GRAPHITE[/COLOR][/I][/B] GXL TD 2.8, ARB Deluxe Winch Bar, 285/65/18, Outback Solutions Drawers, Safari Snorkel, Hayman Reese HD Towbar, Firestone Coilrite Airbags, Bilstein & Dobinson lift, AMTS rear wheel spacer, Redarc Tow Pro Elite, Rhino Pioneer Platform (2128x1236mm) with more to come.

            Comment


            • #7
              Damn, i wish i found this post a month ago.

              what about the BI-BE5-A712 for the front?

              Comment


              • #8
                Originally posted by leont92 View Post
                Damn, i wish i found this post a month ago.

                what about the BI-BE5-A712 for the front?
                Hey leont92,

                The 712 is also a copy of the OEM valving, see here;



                The 712/713 saga has gone on for many years on Pradopoint. Kits such as "platinum Bilstein/Ridepro" were sold to members on the basis they had customised valving for Australian conditions. This was later shown to be false;

                http://www.pradopoint.com.au/showthr...lved&styleid=2

                The only difference in this "platinum" kit compared to OEM valving and coil rates was a stiffer rear 270lb/in coil. This stiff coil rate was poorly matched with the rear 713 valving, with nowhere near enough rebound in off-road conditions. The 713 shock cannot control the stored energy from a 270lb/in coil, and in a packed up Prado this leads to the notorious "pogo stick" dynamics.

                The 712 valving is a copy of the original 120 series Prado strut valving, and it has not changed up to the 150. The only difference is a stiffer front OEM coil rate in the 150 (780lb/in compared to 620lb/in for diesels) which makes the 150 even more of a boat handling wise than the 120 on OEM suspension.

                The most appropriate off the shelf off-road valving/coil rate setup for the Prado in Bilsteins is D563/660lb/in/1478LT/280lb/in. This combination gives enough rebound in the rear with enough critical damping to minimise body roll and "pogo stick" dynamics. The 660/280 coil ratio also gives around 25% for the Olley criteria ride rate ratio and gives a rear frequency around 10% higher than the front, both of which give good handling and minimal kinematic perturbation of the Prado.

                Getting the valving/coil rate correct in the rear of the Prado is the most important aspect of choosing Prado suspension. The front IFS motion ratio severely scales the strut valving at the wheel position and leaves a maximum of only around 15% critical damping possible. As such, having high critical damping at low velocity in the rear shocks and the correct rebound/compression ratio at high speed is vital to good off-road performance in the Prado.

                Unfortunately most sales staff have limited knowledge of how suspension really works, and I continue to hear 712/713 sales pitches to this day. Ask yourself if you would drive a Prado down the Canning Stock Route with OEM valving that is matched to soft coils. Of course nobody would try this if they had knowledge of the valving, which is why you should never buy suspension without asking what the valving is.

                Best

                Mark
                Whitey
                Shockie Maker of the Month Award
                Last edited by Whitey; 20-09-2017, 05:10 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.

                Comment


                • #9
                  Thanks,
                  very interesting/ annoying as i literally fitted them yesterday.

                  so, this is all assuming your running HD Springs? and the it would be slighly better runing standard or MD/ progressive rate spings?
                  im running KTFR-101HT and KTPR-102 which my logic says would be less likely to top out?

                  Would it be worth pulling them out and getting the D563 And 1478LT, While i could potentially sell the A713 & A712 at minimal loss given they are brand new.

                  the D563 and 1478LT's seam to be pretty hard to find/ a lot more expensive.
                  i got my current shocks for $220 per set, ive only been able to find the others for about $440 each set.
                  is there a reason why they are so much more expensive?

                  Comment


                  • #10
                    Hey leont92,

                    I sent you a PM.

                    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


                    • #11
                      Originally posted by leont92 View Post
                      i got my current shocks for $220 per set, ive only been able to find the others for about $440 each set.
                      is there a reason why they are so much more expensive?
                      No, but there is a reason the 712/713's are cheap. Not suited for a lifted Prado, and not valved for Australian roads.
                      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


                      • #12
                        Originally posted by photoprado View Post
                        No, but there is a reason the 712/713's are cheap. Not suited for a lifted Prado, and not valved for Australian roads.
                        Yes and yes!

                        However 712 and 713 have always been around the same price as D563 and 1478LT, must have been a run out sale or something to get them at $220/pair.

                        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


                        • #13
                          Sorry, i stuffed up they where 220 each for the front and 190 each for the rear.

                          Comment


                          • #14
                            Originally posted by leont92 View Post
                            Sorry, i stuffed up they where 220 each for the front and 190 each for the rear.
                            Hey,

                            No problemo!

                            D563's and 1478LT's can be had for very close to those prices when they're on special!

                            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


                            • #15
                              That's what I was going to use, what do you recommend....efs?

                              Comment

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