Re: [doc] Front springs

[John Tien <johntien99@xxxxxxxxxxx>]

Hey Martin,

So if I want to lower my D's rear using the adjustable
shock option (with stock rear springs)... apart from
setting the adjustable collar on the shocks itself,
are there any adjustment I should do to the suspension
setup on the car so it runs properly?

And what is the minimal height the rear of the D can
take before the wheel starts to hit the wheel arch
when going over bumps?

Cheers!
John

--- Martin Gutkowski - DMC Ltd <martin@xxxxxxxxxxxxxx>
»¡¡G

> Hi All (esp Mark)
> 
> I've driven a lot of DeLoreans now, and more than
> one with old front 
> springs on the rear. I also have moderately lowered
> rear suspsnsion on 
> my own car, by about an inch with Grady's (former)
> shock setup.
> 
> 1) Front springs on the rear make the rear too low
> IMO, in fact 
> sometimes lower than the front. Anything lower than
> where the control 
> arms are level is a bad idea IMO.
> 2) On my own car I've eaten 2 sets of back tyres in
> 10,000 miles thanks 
> to the lower setup (toe-in is correct and although
> I'm a fan of 
> wheelspinning, so is Chris H and he's done more
> miles on one set :-) 
> I've got adjustable lower links on my other car and
> the wheels sit 
> noticably straiter at the back.
> 3) A softer ride on the rear makes an unbelievable
> difference to the 
> ability to lose the back end, in a similar, but more
> predictable way as 
> loose trailing arm bolts do. I've recently had two
> cars in at the same 
> time - one Stage 1 and one Stage 2. The Stage 1 car
> (less powerful) was 
> far too tail-happy. The difference was front springs
> on the rear, and I 
> can vouch for the rest of the suspension on both
> cars, and both had the 
> same set of pirellis.
> 4) In playing with the adjustable suspension we do,
> you can make the car 
> thoroughly dangerous (but a great drift machine, if
> you're into that!) 
> by stiffening up the front and softening up the
> rear. It's quite surprising.
> 
> "
> 
> The rear suspension uses the 'Second Order Lever' It
> has its fulcrum and effort(spring) in opposite ends
> and the load in the middle, just like a wheel barrow
> set up.
> 
> The front suspension uses the 'Third Order Lever' 
> The fulcrum and load are at opposite ends this time
> with the effort(spring) is in the middle, such as a
> shovel.
> 
> "
> I'm not entirely sure how you can apply lever
> principles to the rear 
> suspension because as I see it, there isn't one. The
> weight of the car 
> is passed directly to the hub carrier at one end of
> the lever. The other 
> is just a pivot. There's no multiplication involved
> unless you look at 
> the angle of the spring/shock which in this case is
> only non-vertical to 
> get it out the way of the tyre, hence needing a
> slightly stiffer spring 
> than if it were vertical, at a ratio exactly
> proportional to the angle 
> of the spring/damper compared to the vertical (at a
> guess, but it's 
> probably as near to no difference as makes no odds).
> That's "moment of 
> forces" stuff and Newtonian physics, IIRC, but it's
> a while since I did 
> my A-level Maths and Physics!).
> 
> The front suspension is a second order lever,
> although dealing with a 
> multiplication of effort rather than a division of
> it.
> 
> You're absolutely correct that all other things
> being equal, the rear 
> spring can be weaker for the same effort, given the
> geometry. 
> Unfortiunately all other things aren't equal because
> someone had the 
> bright idea of plonking the engine over the back
> wheels :-)
> 
>
http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0017416.html
> 
> Martin

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