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MG MGB GT V8 Factory Originals Technical - lateral stability and roll center, rear axel

Has anyone tried to attach their panhard rod or other stabilizer to the top vs the bottom of the axel to see how handling is effected?
Thanks.
Chris
c l sorenson




Mine is attached slighly abovre the axle; in plane with the bottom of the trunk floor. It makes the car feel a lot more planted while cornering,however, I suspect it has made the car a bit more willing to let the rear out either earlier or more suddlenly.

Pete
Pete

I've been thinking about this one- the panhard would raise the rear roll center, causing greater pitch/roll on the outside tire in a turn, due to the increase angle of the roll axis. This would cause it (the outside tire) to carry greater weight with less negative camber. A larger front sway bar would be needed to compensate for this.

Am I thinking this through correctly, or is my thinking all screwed up?
greg fast

according to Fred Puhn in How to Make Your Car Handle the roll center is effected by the panhard rod only by its attachment point to the axel. A low attachment point lowers the roll center and vice versa. I wonder if anyone has tried both on their cars to see what the real life diference is. I want to increase rear wheel cornering traction. There aere too many variables to predict with certainty that the location of the panhard rod for this application. I was hoping to avoid the reinvention of the wheel.
Thanks, Greg and Pete
Chris
c l sorenson

Gents,

Roll centre is dictated by the panard rod. Assuming it is horizontal the RC should be half way down the rod.

However raising the RC causes a second problem. the spings are forced not only in an up/down motion but also begin to be forced side ways. Imagine the RC 3 foot above the axle, the axle would rotate with a swinging motion, with each wheel moving up/down and side/side.

Assuming the panard RC is above the axle, this will increase the relative rear roll resistance over that of the standard spring rate. Which will then change the ratio of the front roll resistance to the rear. Thus when cornering the rear outer tire will take more load, and loose grip 'earlier', and thus over steer.

Chris - to increase rear cornering traction, I would suggest;
i) Lower the rear,
ii) Increase the front roll resistance (springs or roll bar) - this will trade off with less front grip.

James
James

James
Your comments are in agreement with the Puhn referenced book. My trouble is that I need the panhard rod to keep my tires from scraping on the fenders. Would you suggest that I modify the body instead of attaching a panhard rod? It seems that if I mount the rod low enough, lower the rear and tighten my front body roll that I will be doing well. I have a 3.4L v6 with about 190 hp and good torque. My goal is a car that handles corners superbly and has great 30 to 90 mph times. I am running nissan aluminum wheels which are ofset about an inch wider than stock B wheels. I love the look and the stability they provide.
Thanks for your expertise.
CHRIS
c l sorenson

http://membres.lycos.fr/mgcontact/fileupload/uploads/1108018873_panhard.jpg
I have built my own Panhard rod (aviation pipe 25CD4S).The car on the ground, in neutral position the rod is parallel to the rear axle. The bracket to the rear axle is welded with rose joint to the rod. To the shell the bracket is also welded, with reinforcement into the bootlid. I use Triumph Spit polyurethane bush to the rod. I have also anti-tramp with the same principle (rose joint and polyurethane bush) I have 6x15” wheels and 195/55x15 tyres and not any problems with the fenders lips
regards
michel

Chris,

My comments were a bit of an acedemic indulgence realy, on what would happen to effect spring/roll rate if the roll centre dictated by the panard was raised significantly above the axle.

The roll centre of a pair of leaf springs is at the level of the springs (info from one of Alan Staniford's books). I would therefore assume that a panard installed at this level (as most of the kits do) would not significantly change the RC, and thus roll stiffness and handling should be ok.

I would procede with fitting the panard rod,
Regards, James
James

This thread was discussed between 31/01/2005 and 10/02/2005

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