Re: alfa-digest V8 #237 - Changing the roll center of a suspension

[AlfaNeely@domain.elided]

George,
       I need to dig out my copy of How to Make Your Car Handle.  Maybe I 
ought to read it too! <grin>
      I need to build or buy a panhard bar for my 84 spider race car.  I 
bought a bar from Speedway but have yet to build mounts.  I also plan to 
build a pair of upper control arms so I will have a four bar rear end 
attachment.  Any comments on that?  Should we move this to the Alfa Racing 
list for additional comments?  That is a more appropriate forum than Alfa 
Digest.

       Who's bar are you using?  Jack Beck at 
http://www.orionmotorsports.com/ wants $625 for his weld in bar kit plus $200 
to weld it to the axle plus $400 for the upper link to replace the T Bar.
       I broke down and bought his tubular front sway bar that bolts under 
the steering box.  I am glad it did.  I bolted right in and would have taken 
hours of trial fitting to duplicate it.
       I seems Jack told me once the Panhard bar could be used with the stock 
T Bar.  Apparently the conflicting centering devices do not fight each other 
too much.  Or that was the impression I got.

      I bid on a Tom Zat bar on eBay some time ago.  I bid half what Tom 
wanted for his bar and did not get it.  He charges $295 per his web page at: 
http://www.alfaheaven.com/  However, it appears it mounts at axle level, 
which would not lower the roll center all that far.
      Also how far below the axle is your Panhard bar?  Do you have the stock 
gas tank?  Does your bar attach to the axle on the passenger side?  Jack's 
bar does that so that you can change the drive side axle housing and center 
section as a unit to change gear ratios.

Ciao,
Russ Neely
Oklahoma City



In a message dated 11/19/2001 9:00:38 PM Central Standard Time, 
owner-alfa-digest@domain.elided writes:


> Date: Mon, 19 Nov 2001 21:25:30 -0500
> From: "George Schweikle" <schweikg@domain.elided>
> Subject: Re: Changing the roll center of a suspension
> 
> Nizam,
> 
> I don't have my "How To Make Your Car Handle" book handy, but here's what I
> remember: the front and rear roll center points must be connected to
> establish the roll axis. Think of this as the longitudinal line that the
> entire car rotates around as it leans. This really establishes the basic
> handling characteristic, and to define this axis requires knowing both the
> front and rear roll centers. I'm not sure about the roll axis of a GTV-6,
> but the 105 Spider/GTV has the roll axis angled downward from rear to front.
> This why stock Spiders seem to want to corner on their outside front wheel
> as the rear of the car hikes up. The Panhard bar kits sold for 105-chassis
> cars move the rear roll center from the T-bar attachment at the top of the
> differential to the level of the Panhard bar under the diffential. A drastic
> change of 8-10 inches that improved the handling of my Autocross Spider. I
> believe the GTV-6 Watts link already provides a fairly low rear roll center
> at the center link pivot on the DeDion tube, but don't know how this
> compares to that of the front suspension. Calculating the roll center of
> independant front suspension is more complicated, but the Fred Puhn book has
> some excellent material on this topic.
> 
> How about some comment from the racers out there?
> 
> Regards,
> 
> George Schweikle
> Lexington, KY
> 76 Spider

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