Miata Mailing List: August 1996, Message #125
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   From: searle@pop.srv.ualberta.ca (Searle)
Subject: RE: Subframe braces + How to make your sedan outcorner a Miata
   Date: Fri, 2 Aug 1996 02:44:38 -0400

>You'll probably get a lot of replies, but subframe braces and sway bars
>are two different animals. Braces are merely passive chassis stiffeners
>and (anti) sway bars are active suspension components.

I'm going to split hairs here, but it is all in the name of an interesting
anecdote:  (Anti) sway bars (Hair split #1 - more properly termed anti-roll
bars) are not active suspension components (Hair split #2), since they can
only passively react to body roll.  Active suspension in the true sense,
where hydraulic pistons, actuated by a complex combination of road and
vehicle sensors, totally replace both springs and shocks. 

F-1 used this technology extensively until it was banned  a few years ago,
and Lotus Engineering Group (among others) was devising a system for road
use.  Sadly, it never saw production.  The only North American production
car that I know of to make use of some of this technology is the Infiniti
Q45 with the (really expen$ive) semi-active suspension option.  Semi-active
because the piston wasn't capable of supporting the full weight of the car
at all times, and so relied on a regular coil spring at each wheel.  Cost
and power considerations (the hydraulic pump required really puts a load on
the engine) resulted in this compromise

So, here's the interesting anecdote:  
        
        How about a bone stock four-door sedan - equipped with all the usual
luxury items, including a boulevard-soft suspension that can put most
Cadillacs to shame - that can pull over 1.0G on the skidpad?

Well, Citreon, the French company that builds all those weird cars that you
can't get over here anymore, had a really brilliant idea on how to overcome
the compromises most manufacturers have to accept when they install
anti-roll bars.  To whit:
                * strong anti-roll bars prevented body roll, but played
havoc with the ride quality under certain circumstances.
                * weak (or no) anti-roll bars allowed the ride to remain
cushy, but the resulting body roll played havoc with suspensions geometries,
etc.

Well, Citreon didn't want to compromise ride comfort.  After all, their
hydraulic suspension design was so forgiving that you could literally drive
over a speed bump at speed, and barely feel it (I've actually experienced
this sensation, and it's uncanny).  Their solution to the problem was to
design an 'active' anti-roll bar end-link that could automatically adjust in
stiffness, much like many adjustable bars sold on the aftermarket, only more
quickly, and involving less grease on the driver's collar.  In full-soft
mode (for comfort) the link was essentially disconnected, and motion from
one wheel was completely isolated from the other.  Full-stiff mode, on the
other hand, allowed essentially no body roll at all.  Thus, the tire could
stay as close to vertical as possible, and allow the maximum stiction - in
this case over 1.0G on stock tires.

Photos of the car going around a corner looked really weird.  Without the
stock car next to it dragging its door handles on the asphalt for comparison
purposes, you would swear that they merely took a photo of the car while it
was standing still.  Drivers were continually amazed at the average speed
they could maintain down twisty roads, without the usual drama, and without
complaints from their passengers.

Moral:  If you need to carry more than one passenger, and don't want to
compromise on cornering fun, import one of these beauties.  So what if you
can't get any parts for it when it breaks down.  You could always pretend
it's British.

Steven Searle

'93 Black & Red L.E.

Q:  Why do the British drink warm beer?
A:  Because they have Lucas refrigerators.