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Rear Leaf Spring Elimination Kit


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I don't recall any kit either but I know there have been efforts to do so. Do a Google for Corvette five and six link suspensions as that's been done a lot. But then, with your experience you probably don't need those illustrations.

 

Bear in mind that such a mod will be OK in SCCA but will be frowned upon should you want to go Vintage....Steve

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Thanks for the input. I will undoubtably design my own system, but I wanted to see what's been done before. I need to make sure it will pass SCCA tech, so I have more research to do. Something has to be done to tame this evil handling car, and it seems to be due to the rear suspension set up I have. (main leaf spring only, spaced up 1" on the diff, Spax coil overs w/400lb springs, 240Z half shafts and adjtable lower wishbone)

 

Clark

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Evil handling in what way? What sort of toe, camber and rear caster angle do you have? The latter is effectively set by the angle of the diff - which usually needs to be nose down for the right result - which tends to be at odds with what your driveshaft (propshaft) UJs would want.....

 

400lb at the rear seems quite high though I guess the angle means you are not seeing all of that.

 

My other thought is that the single leaf may be too flexible and is allowing the top of the vertical link to move around under load. IMO the KD TRiumph upper link (and Prirace too) will suffer from the same problem due to the inner pivot being single, narrow and a long way from the outer pivot. It will need to be extremely stiff fore and aft or once again the outer end will be all over the place. Also unequal length wishbone setup tends to have the upper link shorter than lower as it helps the camber change go in the right direction.

 

It's perfectly possible to get these working pretty well with the transverse spring.

 

Nick

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Excuse me for interupting , but from what I have just been reading , does it not make sense as a relitivly simple step to first ensure that at least the lower wishbone is ' very stable ' , thus ensuring the VL is therefore also very stable , at least in the fore/aft plane . I realise this is only part of the weakness but even this will surley make a welcome improvement on the origional system .http://cl.ly/image/0c3N0r2Z0i0U

I am finaly expecting these modified MGTF VLs and simple ally wishbones back from the engineers [ powder coaters ] this week . I realise the wishbones could be improved upon but at least they should achieve the principle I am talking about without any weight gain and can be redesigned later .

I will post some pictures on their return as I am fully aware of some members considerable knowledge and am fascinated to hear any feedback/suggestions . Matt .

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The Ro-Spit originally had the the upper link on the top of the diff. they felt under hard cornering (the car was built to Autocross) the diff. was flexing and allowing camber changes. So they built a support for the upper link that attached to the chassis and the upper shock support

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Thanks for all the input guys, now we are going to set the car up and measure 3D coordinates of all the front and rear suspension points to figure wheel rates and other figures to determine what need to be done relative to these fixed dimensions. Then I will decide about some way to stabilize the upper portion of the rear upright that will be "legal" in SCCA - I am chasing info on the most successful Spit chassis in the country (Steve Sargis) to see what he has done, because he has won several national championships and been well scrutinized. Steve Smith has told me he has been able to get the leaf spring set up to work fine - after years of tweaking...which confirms Nick's comments.

I do suspect that using only the bottom leaf of the spring has weakened it torsionally and may be a large part of the problem.

I will keep you lot updated.

 

Clark

 

my set up:post-1494-0-75421000-1349876607_thumb.jpg

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Lincspeed,

If you are going to all that trouble, for goodness sake junk that enormous,heavy Rotaflex wishbone!

At half of it unsprung weight, it will make your new suspension much slower to respond with lower wheel rates and stiffer springs needed to control it.

It's extraordinary how lightly built a fabricated wishbone need be, when compared with that boat anchor.

John

 

PS Please compact your pics when you post - but I'm so envious of your drawing ability that its' good I can't see the drawings. J.

post-690-0-02044100-1349889683_thumb.jpg

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John, that is certainly part of the job this winter. Those are quite fancy ones you shown above, I will probably just replace the wishbone with a three point tubular part with rod ends. I could also see a performance improvement by replacing the heavy 240Z half shafts with light weight drilled half shafts and CV joints...

 

Clark

 

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Not so fancy!

All the sphericals are adjustable, of course, but the two to the upright are adjustable on the car.

The one to the side is for the radius arm, and on the other is a threaded tube for the shocker bolt.

You don't need that on your's. What's your upright?

Do you have a radius arm??

JOhn

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The VL/upright is Mgtf .

You are correct one side of the wishbone would have to be disconected to adjust , not a big issue .

I agree that a redesign to something even lighter at some point would mean lower unsprung weight .

No I am not intending to use a radius arm just two strengthened mounting brackets either side .

I shall see if I can pick these up today and post the results .

I am NO engineer quite obviously hence the basic wishbone design , just trying to use basic parts which are somewhat of the belts and braces selection as even now when I look at my Canley front upper wishbones I can not believe the tiny weld area on the butted joints is strong enough for the job even though I know it must be .

Next job is having shafts made up to link the Subaru and Mgf CVs .

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Spit 131- name? Anyway, I look forward to seeing photos of your new parts, I'm not sure what I'm seeing in the drawings...

John - My upright is the stock cast GT6 part (machined to take the 240Z shafts) - as far as I know. It came with the car when I bought it and that was my understanding. Your custom A arm design with the shock stud is not a bad idea, as it would allow me to fit a longer shock. If you look at the photo, you will see how short the shock is I'm using.

 

Clark

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AAaaaah, so!

Two conversations at once.

 

131,

I know of a very successful mod that uses two modified radius arms instead of the wishbone, located by brackets as far apart as possible on the chassis rail, onto a conventional Triumph upright. opwner swears by it, and it looks very good. You say, "two strengthened mounting brackets" - is that what you are doing?

But a wishbone, and an inverted wishbone at that, located at the chassis rail at a single point, you must have another control arm, else your toe-in will be all over the place.

 

Linc,

That was the plan!

 

John

post-690-0-56794300-1349966740_thumb.jpg

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