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HI ALL:
After reading threads and speaking with builders of the 5exi, it appears that there is a fundamental design fault with the rear suspension on the early cars, of which I believe my chassis/suspension is!
Maybe even a dangerous design that should have been recalled to address!
I am sure Mark from Marlin will no doubt give his 20 year industry experienced view.
I see a few people have addressed this issue in various ways.
Has anyone thought/tried to modify a production car rear setup such as MGF/ MGTF?
I was thinking of using the uprights and modifying my wishbones, retaining the coil over shock set up if using the MGF.
And if using the MGTF the radius arms, lower arms and modifying the Marlin top wishbone. Again retaining springs/ shocks.
I could move the pick up brackets on my chassis as I intend to have it blasted and re powder coated as the factory light grey is so thin it has rusted before even seeing the rain!
Any thoughts from you experienced builders would be appreciated
To be honest I wouldn't bother modifiying a production set-up. Depending on what your application is for the car it may be worth while waiting for Track Developments to complete the "bolt on" kit and then use that.
Track Developments contact details are below if you would like to discuss the issue with them in greater depth which could be beneficial to you,
Dave Cooper - 01666 840482 - Evening Enquires
Dave Gallop - 07977 948883 - Technical/Workshop
The original geometry rear upright, has the ball joints approx 100mm apart, with one upper ball joint mounted directly above the bottom ball joint, the other mounted on the rear of the upright.
This earlier design has quite unpleasant bump-steer characteristics, and also compromised toe stability, due to the small ball joint separation.
The later design, includes an upright, which is more like a V when viewed from the side, and has the ball joints separated by approx 200mm. The later design I understand resolves the bumpsteer, and toe stability issues.
There are, depending on who you speak to, further issues with both of Marlin's designs. I believe Marlin consider the later rear uprights and the corresponding upper wishbone, provides a car that is very well resolved. I haven't driven one, so can't comment. John (limpabit) has a car in this configuration.
The view of some others, is that even with the bumpsteer and toe stability addressed, there remain fundemental geometry issues, that compromise the car's abilities.
From the old threads, you'll no doubt have clocked what my opinion is. In short, from the books I've read (initiated by my unhappiness with my car's handling as sold), I'm of the opinion that Marlin's geometry doesn't follow typical text book rules, and thus has undesireable properties of a high roll centre, along with poor dive / squat properties (there are other issues, but these are the main 3). This is my opinion, and all I have learnt has been from books / conversation. It could be I'm wrong, Marlin are right.
The only person I think to have sat in a heavily modified car (mine), and a car equiped with Marlin's stage 2 suspension, is Limpabit's friend, Ian (another 5exi owner).
As a slight aside, whatever route you choose, get the suspension (I mean arms, uprights, and shocks to provide the correct droop / travel) chosen BEFORE you drop the engine in, and start to play with driveshafts. I've learnt to my cost this evening, that one of my bespoke shafts is too long for the latest round of suspension mods I've made. A costly error!