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  • Roadster Front Suspension.

    Hi,
    I haven't posted here before but would be interested in anyones experience or thoughts.
    I've been slowly rebuilding a Marina based Mk2 Roadster and would love to change the front suspension to the earlier Triumph set up. I've also considered MGB as one would have larger discs and wire wheel hubs. Has anyone done this before ?

    Regards, Brian.



  • #2
    Re: Roadster Front Suspension.

    An idea that has often been raised.
    The main difficulty is the differences between the chassis shown at.


    IMHO the standard Marina front end suffers from two things, a bad reputation from the press demonstrator Marinas that prompted a redesign on the production runs, and poor maintenance over the following 40 years, though there were attempts to improve things by fitting anti-roll bars to the Itals.

    Checking that there is no wear or excessive play in the suspension or steering components, replacing the various bushes with Superflex ones http://superflex.co.uk/products.php?cat=234 especially the tie rod bushes works wonders. http://www.fastmarinamagazine.com/in...hp&f=13&t=5222

    If you want bigger/better front brakes, try my Clio conversion that can be built from lightly modified standard parts to fit either 13" or 14" rims. http://www.marlinownersclub.com/foru...=21&do=discuss

    Hope this helps
    Last edited by stevejgreen; 20-01-13, 08:43 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.

    Comment


    • #3
      Re: Roadster Front Suspension.

      Hi Brian good to here from you, without major surgery to the front chassis it would be quite difficult to change over. As Steve says poor maintance is the reason the marina suspension has problems.
      If you are intersted I can give you details of the suspension mods I did on my roadster to overcome many of the design issues the marina based roadster has like negative camber, unequal front wheels, not enough caster so the steering self centres and poor brakes. You can also get hubs that allow knock on wire wheels to be fitted
      Then we can start on the rear suspension and that also sorts out many issues
      Lee
      Last edited by CosworthCabrioLee; 20-01-13, 08:34 PM.

      Comment


      • #4
        Re: Roadster Front Suspension.

        Welcome Brian,

        I would have thought it would be reasonably easy to fit a more capable front suspension if you are good at engineering. Why stop at Triumph? I would have thought the Cabrio suspension is probably capable of being adapted to the Marlin chassis, The MGB would not be so easy because of it's construction, you would probably need to graft the entire front chassis section. I think a lot depends on what you intend to use the car for and approach the options from that end.

        With the very solid chassis the Roadster has the options must be very wide. I see it as a hugely versatile platform open to a wide range of options.

        That said with proper maintenance and care the standard Marina suspension works well enough, partly because a Marlin is much lighter than a Marina, the components are well under-stressed, as are the brakes.

        You have the choice to run with the pack and use what you have or mod what you have else get the cutting torch and welder out! Choices!!! If you do get adventurous you need to very carefully consider all the implications and possible snags.

        Comment


        • #5
          Re: Roadster Front Suspension.

          Hi and thanks to everyone who came back with their thoughts. I'd just like to say that you all came up with valuable and sensible opinions which is a very nice change from a forum I was once on .

          Firstly the reasons I'm not that happy with the Marina set up on my Marlin are that to my mind the front track is too wide and even with quite sensible tyres is bordering on what is passable for for the Road Traffic Act if a traffic policeman for example ever wanted to get difficult. Secondly is the stiffness of the front end.
          there is next to no movement, I weigh 80 kilos (shame) and produce about 1/2 inch deflection when I stand on the front bumper. As the spring rate for the back end is fairly soft there is a definite lack of balance there. I have nothing against torsion bar suspension. If it was good enough for the D type and others it's O.K. for me too. I believe my donor Marina was a van and the PCDs are 3 3/4 so it was the smaller version.

          To soften the spring rate I could change the torsion bars to a smaller diameter, any idea if Morris Minor saloon would fit ? To machine them down would be a stab in the dark which with the difficulty of replacing them I'm a bit unwilling to take.

          When I first bought the car it was twitchy to the extent that it felt ready to swap ends and there was no self centreing , it's a lot better now with a couple of mm of toe out and a bit more caster. However I feel that properly it should have toe in to preserve stability under hard braking. It's all in good mechanical condition but I think you are right about improving the tie rod bushes especially. I'm not running it down because it's an old design I just think we could do better now.

          I rather like the Triumph suspension as it allows a lot of changes to geometry and spring and damper rates and worked pretty well for Lotus and others in the past. MGB frony suspension is attractive because it's easily available and cheap and also gives you a wire wheel hub with the right relation to the kingpin. Rather than use the whole front subframe I had thought of bolting the lower wishbone to the Marlin chassis and using a coil spring damper and a fabricated top wishbone, but this hasn't got to the stage of offering up components etc.

          Probably I'll carry on with the Marina set up for the time being but would welcome your advice on improving the camber and castor etc

          Thanks again for all your help.


          Best Regards,

          Brian.

          Comment


          • #6
            Re: Roadster Front Suspension.

            Hi Brian,

            Not quite with you on the front track being too wide? Might that not translate into the original builder putting the front wings too high, therefor too narrow. My front wings are borderline to the edge of the tread and I only have 155 13 tyres on at the moment. I am looking to lower the wings about an inch which will widen the front coverage significantly. If you measure the cars width of the rear wings and compare that measurement with the width over the front wings, that may tell a story. I think mine are about three inches narrower at the front than the back. If it passes the MOT as is then a I understand nowadays a policeman is likely to require a retest if he feels it's borderline, rather than prosecute on the spot.

            One simple mod which I have heard works wonders is to change the bushes to one of the grades of the Polly Bushes.

            I am with you on the stiffness, I don't know if Morris Minor will fit, the splines may be OK, but the length may well be different. Why not get hold of some spare torsion bars and thin them down a bit. An engineer should be able to work it out , DogonCrazy worked my spring rates out for my Marlin from basic data. I would expect it could be even easier with a torsion bar. What about retaining the Marina suspension but use a coil spring damper like the Triumph Herald unit. The mounting might need altering a bit but nothing too radical.

            There is scope for adjusting the castor and camber by elongating the mounting holes for the top arm and making some sort of adjuster to position the pivot shaft in or out at each end, independently, which could well give you all the adjustment you need? That's what we used to do to get neg camber on the Mini's, front and rear. I have to admit I have little experience of the Marina suspension so these are merely ideas gleaned from past experience and basic principles.

            Out of interest what part of the country are you based? Not that it matters but you might be almost on somebody's doorstep!

            Comment


            • #7
              Re: Roadster Front Suspension.

              Hiya

              We have a member who has removed the Torsion Bars completely and replaced with adjustable Coil Over Shockers which allows for ride height and softness to be adjusted.

              Adrian

              Comment


              • #8
                Re: Roadster Front Suspension.

                For torsion bars I only know of two variants.
                21H5437 Heavy duty 20.6mm / 0.812" Dia
                21H5747 Normal duty 19mm / 0.75" Dia
                Measured in the middle as the splines at either end are the same on both.
                Morris 1000/Minor torsion bars will not fit.

                Depending on the front shock absorbers you have fitted, it may be worth replacing them with Spax adjustables, certainly they make an improvement to the rear suspension.

                I am not convinced that removing the torsion bars and replacing them with coilovers is a good idea. The whole of the front of the car is supported through the torsion bars and to use Coilovers relocates that load to the top shock absorber mounts that were never intended to carry the full weight of the front of the car. That is not to say that it cannot be done.
                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.

                Comment


                • #9
                  Re: Roadster Front Suspension.

                  Taking the liberty to insert the link to the thread which Adrian kindly dug out, in order to make cross reference easier in the future.



                  Having thought about it maybe reducing the diameter of the torsion bars by machining them might not be a good idea because they are forged, forging induces a grain structure in the steel part and also a 'skin' which influences the strength of the part. Machining that 'skin' away could compromise the reliability of a particularly critical part of the suspension, a breaking torsion bar is far worse than a broken coil, which would usually only collapse by about one coil or so.

                  If you added a 'strut brace' between the two suspension towers I see no reason why it wouldn't be OK, after all the top link is mounted on the tower and stiff shockers can impose a fair hammering on their mounts. I think I would want to improve the lower bracket mount where it attaches to the bottom link perhaps?

                  Choices! That's what I love about these cars.

                  Comment


                  • #10
                    Re: Roadster Front Suspension.

                    Good point Robert. There was an Australian Marina owner who was considering getting some special torsion bars made. Not sure if it came to anything. I think he was going heavier rather than lighter as he was fitting a straight six, but the costs will be almost identical.

                    Meanwhile, a couple of pics of a coilover conversion.


                    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.

                    Comment


                    • #11
                      Re: Roadster Front Suspension.

                      Hi Brian give me a buzz sometime and I can talk you through what I did which cured all your problems you have. 07720398794
                      Regards
                      Lee

                      Comment


                      • #12
                        Re: Roadster Front Suspension.

                        Wow, what an impressive font of knowledge I seem to have tapped. Thanks for all your posts and Steve I live near Arundel in West Sussex and don't know any other members down here. I did see a red Roadster in Sainsbury's car Park in Chichester last summer but didn't manage to catch him !
                        I don't know how similar the Cabrio chassis is to the Roadster and what could be adapted but would be interested in knowing what might be possible. My wheels 5 1/2 J x13 and the tyres are 175 which brings the tread almost to the edge of the wing, I'm not much of a fan of fat tyres but feel this width is about right for the car.
                        I'll strip the suspension and fit Superflex bushes and probably a rose jointed tie rod and forget about anything much more radical involving taking a grinder to a functioning motor car. I'm very tempted to try a pair of adjustable coil overs in place of the current shocks but had reservations too about loading the struts up, a brace similar to a modern cars suspension brace would be ideal but a bit difficult to fit without cutting the bodywork about. Possibly thicker wider sides on the strut feeding down into a cross member under the chassis might do it.
                        Moving on to the rear suspension I thought a reasonably easy mod might be an 'A' fame from the diff centre to the forward spring mount area. It would be similar to the old Lotus Cortina set up which worked well. However I'm not too sure how you would mount on to the diff casing.

                        Regards, Brian.

                        Comment


                        • #13
                          Re: Roadster Front Suspension.

                          A Watts linkage and anti tramp bar at the o/s or both sides would get the job done. Welding brackets to the axle on spreader plates would be the way to do it.

                          A couple of pix of a Rally Marina anti tramp bars. Not rocket science but for normal road use I question the need with an 1800 engine.

                          Marina Tramp Bars 1.jpg

                          Marina Tramp Bars 2.jpg

                          Comment


                          • #14
                            Re: Roadster Front Suspension.

                            Ok My last bit on this subject.

                            The Morris Minor boys seem to use this kit when updating the front supension from;

                            JLH Minor Restoration Ltd., The Old Coal Yard, Folly Lane, Napton, Southam CV47 8NZ UK

                            Front Coil-Over Kit
                            We developed the wide A arm coil-over kit as an alternative to the established method of up-rated torsion bars and telescopic dampers, which usually give a rather 'pitchy' ride characteristic. Three years of development saw the kit released in 1996, and it has proven to be a hit with the owners of cars with up-rated engines.

                            minor.jpg

                            overA.jpg

                            The kit is adjustable for full geometry set up and utilises the original king pin, trunnions and lever arm damper, which is now only used as a as a pivot point. The torsion bars are removed completely and are replaced with a bespoke weld on chassis bracket and extra cross member between the chassis legs.
                            The AVO coil overs are located through a wide section A arm which offers excellent location. The top mount is weld on and incorporates two strengthening plates to spread the loadings and reinforce the bulkhead cross member. The kit is adjustable for ride height and damper rate and offers a very compliant ride, but should be seen as a sports derived upgrade.

                            Or you can contact Steve Holder of Fourtune Engineering on 07973 128189 and get a Rear Axle Tie Bar Kit for around £100.

                            Adrian
                            Last edited by listerjp2; 23-01-13, 07:27 PM.

                            Comment


                            • #15
                              Re: Roadster Front Suspension.

                              Is Steve still in business? I thought he'd retired a while back...
                              Marlin Roadster, LWB...1860 B Series + Ford Type 9
                              Renault Espace 54mm front calipers, vented discs, cycle wings and adjustable tie-bars.

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