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Re: Rear suspension

To: vinttr4@FORBIN.COM, friends of Triumph <fot@autox.team.net>
Subject: Re: Rear suspension
From: R John Lye <rjl6n@uva.pcmail.virginia.edu>
Date: Wed, 5 Mar 97 07:17:43 EST
Hi Jack,

On Mar 4,  7:31pm, Jack W Drews wrote:
> I am surprised that connecting / disconnecting the rear sway bar has
> such little effect on over/understeer, and inside rear wheel lifting.

Just curious - are you using the Addco sway bars or something else?
For what its worth, when we were working on the suspension of my
TR-4 autocross car (admittedly a somewhat different setup than you'd
want), Bill Lambros did a bit of computer modeling for me.  He
determined that the Addco front bar added about 7-10 pounds per
inch of roll stiffness; as you can imagine, with stock springs
at 290 lbs/in and uprated springs going up to as much as 480
lbs/in, the Addco front bar does little except look good.  I don't
remember the numbers for the rear bar, but it added somewhat more
stiffness, hence its terminal oversteer problems (in my car 
anyway).  We ended up using a very large front bar to balance a
stiffer than the Addco rear bar.

> I am running one extra leaf in the rear springs and am beginning to
> suspect that this makes the rear spring too stiff 

Maybe for road courses, but its partly the front to rear balance,
and the balance between the springs and shocks that all needs to
be accounted for.  That is, if you stiffen the springs, you'll
need to stiffen the shocks, too, so that the springs aren't underdamped.

> which would indicate that different
> length shackles change this.....how about opinions on that too?

I'd be curious to hear about this, too, since I've done no
experimentation with shackle lengths at all.

John Lye

rjl6n@virginia.EDU
http://avery.med.virginia.edu/~rjl6n/homepage.htm

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