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Roadster Front Suspension.

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  • #31
    Re: Roadster Front Suspension.

    An article on this subject would be great for Pitstop.

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    • #32
      Re: Roadster Front Suspension.

      During the 1980,s Jim Jackson done away with the torsion bars. He introduced a Triumph bottom wishbone and coilovers. As I remember he welded a length of approx 80x 50 to the underside of each chassis rail to be able to get a mounting position of the correct height for the bottom wishbones. Terry Dutton went down a similar route in late 1980,s but he had the bottom arm fabricated and much beefier, but picking up on the existing mounting points and used a tie rod , and wishbones. Both of these mods are well covered in magazine articles and kitcar press etc.

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      • #33
        Re: Roadster Front Suspension.

        Sorry Chris. I could not remember the source of the pics I published, otherwise I would have given you credit.

        One thing that comes to mind, is whether it was necessary to cut the torsion bar. Apart from corrosion/paint there is nothing holding the remaining splined end in the Lower arm. You could probably get away with simply extracting the torsion bar as a complete part, giving you the option of refitting it. If I were to do the job however I might leave the Torsion bar in place and replace the Chassis end Lever arm, with a bronze bushed part, allowing the Torsion bar to twist freely. This would keep the suspension looking more standard.

        I dare day that Steve Holder's adjustable Tie rods are an improvement, but my findings were that well maintained Superflex bushes are enough. A comparison might be drawn with the commercially available Classic Mini uprated Tie Rods that have a similar function but are not rose jointed.
        Last edited by stevejgreen; 27-01-13, 02:36 PM.
        MOC member since 05/97
        1984 Marlin Roadster SWB.
        1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
        Three core radiator, Renault Clio vented front discs.
        The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

        Loads of Marlin Reference can be found documents here or there.

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        • #34
          Re: Roadster Front Suspension.

          Good point about using a bronze bush Steve. That would definitely be a good option. However, the main point for removing the torsion bars altogether was because when I fitted the Fiat Twin Cam engine I needed to get the engine as low and as far back as possible to allow for bonnet clearance, given that I was using the standard carb setup. This meant that the new engine mounts would not clear the existing torsion bars so the decision to remove them altogether was sort of made for me.

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          • #35
            Re: Roadster Front Suspension.

            This has been a very useful discussion and it's nice to hear from Chris that he has been using coil-overs for a couple of years without chassis problems.

            I've pretty much decided not to go as far as replacing the front suspension for the time being at least but to use similar coilovers and leave the torsion bars in place backed off to close to the lowest setting and use them as bump stops which would relieve any big and sudden loads on the shocker mounting.

            Another query I have though is 350 lb springs sound a bit on the stiff side, I was thinking of more like 300 lb. My engine is MGB which is probably heavier than the Fiat. Westfields and so on seem to have springs in the 200 - 225 lb range. Anyone got any thoughts ?

            Brian.

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            • #36
              Re: Roadster Front Suspension.

              Yes, but my battery is running down:-(

              Don't confuse the spring rates with the imposed load, the suspension has leverage which throws more load onto the suspension spring than it seems at first sight.

              Sorry to be brief but almost out of battery.

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              • #37
                Re: Roadster Front Suspension.

                Hi, I would just like to come back to the subject of Marina front suspension geometry as I was at the Goodwood Breakfast Club this morning. Amongst all the lovely stuff there a couple of Teal Bugatis with Marina suspension that caught my eye. What was noticeable was that the bottom arm was parallel with the ground as were the top wishbone and steering arms. In other words perfect geometry. Was the Marlin designed as it is for extra ground clearance for trials or because of the 13 inch wheels ?

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