[DeTomaso] Springs

[Göran Malmberg]

Pantera has aggressive camber compensation, especially if it is 
lowered. If we assume that the lower A-arm is parallel to the 
ground, so with a further lower car (or more roll) the upper 
A-arm will get to much angle and we therefore require a bit 
harder springs. But we gain back a little grip through the 
lower center of gravity. By making the car lower we will also 
lower the rollcenter, which may make a bit more swaybars 
necessary. Now I have not talked about the car's balance, which 
is a separate issue. 
Another thing with the Pantera is that it has a lot scrub both 
front and rear. If the car is made lower the upper A-arm will
get an aggressiv angle that produce a very short instant centre.
The Ic/scrub distance leverage lessen the spring wheelrate so a
lower car will get a reduced motion ratio, thereby needing more
spring constant for the same wheelrate.

Tricky and compelx stuff here, but dont get alarmed, just look at 
it as a guidlene for making a decision in the right direction.
Goran

-----Ursprungligt meddelande-----
Från: John Taphorn [mailto:jtaphorn at kingwoodcable.com] 
Skickat: den 18 oktober 2009 15:03
Till: Göran Malmberg; arkoch at earthlink.net; detomaso at realbig.com
Ämne: Re: [DeTomaso] Springs

Goran

I appreciate you insight on suspension.  I was not aware of the geometry

issue being the determinate.

Is the Pantera applicable takeaway in your comments that stiffer vs.
softer 
springs rates are better since the chamber and bumpsteer change 
significantly on a Pantera as the suspension compresses?



JT
----- Original Message ----- 
From: "Göran Malmberg" <hemipanter at hemipanter.se>
To: <arkoch at earthlink.net>; <detomaso at realbig.com>
Sent: Sunday, October 18, 2009 4:24 AM
Subject: Re: [DeTomaso] Springs


>
>
> How we should choose springs depends on how much grip the tires
> produce, because that is what gives the loads the springs will
> have to take care of. Generally speaking, the softer suspension
> gives more grip and harder provide less grip, speaking strictly
> from a spring perspective. The problem with soft springs is that
> it is difficult for the suspension to provide the proper camber
> over a long wheel travel, and if the geometry is not designed
> for the suspension travel in question, the tires will lose grip.
> In that case, we lower grip with harder springs, but even
> destroy grip with softer springs because of a less suitable
> geometry. So the question is how soft srings, we can use before
> the wheel geometry is wrong versus how hard springs we must have
> to cope with the loads that the tires are capable of producing
> (with the right geometry). It is easy to find oneselves ending
> up in the catch-22.
>
> So what should we do? I think we should be restrained with spring
> changes. If we have lowered the car or that we are experiencing
> the suspension bottoms out, as well as if stickier tires is used
> it's idea of tougher springs of say 20%. But we can also imagine
> to change shock absorbers for some more compression damping and
> less rebound damping.
> Goran
>
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