RE: Delrin or poly...

[JustaxPHX@aol.com]

>Thanks for the info on the upgrades!  My only question is that doesn't
>stiffening the Panhard rod so that it will not flex make any anti-roll bar
>unnecessary?  It was my understanding that the Panhard rod was serving the
>purposes of an anti-roll bar on the rear suspensions of the older FWD cars

On the 4k and Coupe models, the rear axle beam does double-duty as the anti-
roll bar, not the panhard rod.  The beam is U-shaped and is designed to twist
under cornering loads -- in fact, it's officially referred to as a "twist-beam
axle" in an SAE paper I have on it (thanks Graydon!) -- and by varying the
stiffness of the axle, you also vary the stiffness of the a/r bar.  You can do
this the easy way by simply welding a piece of .125" flat steel plate about a
foot long across the center of the channel and then drill holes in it as
necessary with a 1" hole saw to make it softer ... btdt.

If you think things through further, you'll quickly realize that because the
axle beam is mounted between the rear wheels, in order for it to be twisted,
the trailing arms have to be somewhat flexible in the lateral plane, which is
why they're made from flat steel plate ... they're fairly stiff in the
vertical plane but flexible in the lateral plane.  Because the the panhard rod
is angled forward and upward, analyzing its behavior is difficult because any
movement causes the axle to move laterally as well and unequally from side-to-
side ... this is one of the many reasons why these cars tend to corner better
in one direction than the other (and it's not the way you might think,
either!).  In any event, given the basic design of the suspension, stiffening
the panhard rod will simply cause the suspension to bind up mechanically and
since it needs compliance in order to work properly, this strikes me as a move
in the wrong direction.

Although I haven't driven any 4k/Coupe with a modified panhard rod and an
added-on a/r bar, my educated guess is that it probably makes things worse, at
least in an absolute sense.  For normal street driving -- do I hear 8/10ths?
-- I suspect it will make a positive improvement in handling; however, if you
push it harder than that -- we're talking autocrossing or lapping a race
course -- then you'll find the car takes on a two-stage character since all
bets are off once the inside rear wheel lifts off the ground.  (Remember, once
you've got a wheel hanging in the air, the a/r bar makes no difference since
there is no weight left to transfer!)  On my old '81 4k, in fact, I eventually
removed the stiffening plate across the axle channel because we found the car
was not any quicker with it (besides which, it was also an illegal mod for the
class we were competing in).

JG