[ Post a Response | Galaxie Forum Full-size Ford, Lincoln, and Mercury ]
When posting a question about your Galaxie or other Ford (all are welcome), BE SURE to tell us what it is, what year, engine, etc so we have enough information to accurately answer questions.
Posted by Daze
on April 27, 2009, 2:44 pm, in reply to "Panhard bar geometry"
69.145.220.22
First the disclaimer 
Of all my suspension projects to date none of them has had a Panhard bar so I am not speaking from hands on experience. However all my suspension projects to date have given me a complete enough understanding of suspension that I believe I can answer your question.
You are correct, both options will solve the problem but assuming the change in ride height is not to drastic from stock, in my humble opinion one option is better than the other. I would make the bar adjustable and then lengthen it to the desired length. This would not only be the easiest, and allow for future adjustment if you decide to change something in the rear suspension but should also provide handling that is equal to or better than the way the car currently handles.
A Panhard bar is an independent arc which means, its movement is unaffected by any other suspension arc’s movements. To better explain what I mean by an independent arc, lets look at an IRS unit where the arcs are NOT independent. On an IRS unit the length of the UCA, from its inner pivot to the outer pivot, is the radios of a circle that has a specific arc resulting from that radios. In the same way the length of the LCA from its inner pivot to the outer pivot is the radios of another circle and has a specific arc resulting from that radios. Those two arcs work together to create a third arc, which in an IRS unit is the arc the hub moves along. In most cases the radios and corresponding arcs of the LCA and UCA are different. That means if you change the length of either the LCA or UCA a specific amount, you must calculate how much to change the other to maintain the correct hub arc and camber curve. The reason I go in to all this is, as I said before the arc of a Panhard bar is independent and being independent it does not suffer from the complication of incorrect suspension geometry when you change its length.
By lengthening the bar you increase the radios and in doing so decrease the arc. Basically the longer the bar the less change in side-to-side motion. To put it in extremes (made up numbers to illustrate the point) a bar 100’ long may only move 1/32” from side to side with 4” of vertical travel where a bar 2’ long may have a full inch of side to side travel with the same 4” of vertical travel. With that said the reason you want the bar to sit level at normal ride height is so that as the suspension compresses and extends the rear end moves an equal distance toward the frame pivot weather it is in a state of compression or extension. In other words (once again totally made up example with made up numbers to illustrate my point), because of the arc of the bar, 1" of suspension compression from normal ride height may pull the rear end 1/8" toward the frame mount and in the same way 1" of suspension extension from normal ride height will mirror 1” of compression and also pull the rear end 1/8" toward the frame mount. If the bar does not start out level the amount of movement will not be the mirrored. With the bar at a slight angle that same 1" of suspension compression from normal ride height may pull the rear end 1/16" toward the frame mount but 1" of suspension extension from normal ride height would pull the rear end 3/16" toward the frame mount.
The good news is as I said before by lengthening the bar the arc decreases which means the amount of side-to-side movement is also decreases so even though unbalanced by not being level at normal ride height, by lengthening the bar you might get 1/16” movement toward the frame mount in compression and 1/8” movement toward the frame mount in extension. If the car is handling fine in its current configuration where the bar is at an angle than lengthening the bar will only improve handling and correct the issue of the rear end not being centered under the car.
Leveling the Bar by extending the brackets will also fix the problem, but it does not have the benefit of a decreased arch. Also by lengthening the bracket you are moving the bars mounting point away from the frame which will increase the leverage on that mounting bracket requiring you to build the longer bracket stronger than the original. The only real advantage of leveling the bar is to mirror the movement.
All that said I would be willing to bet that with either option the change in handling is probably negligible. Unless you noticed a serious loss in handling by raising the rear end neither option should have a significant effect on handling with the only perceivable change being that the rear end is correctly centered under the car. With that in mind lengthening the bar is the obvious choice because it is easier and will provide future adjustably if needed in the future. I tend to get long winded and bogged down by details so if any of my rambling doesn’t make sense please don’t hesitate to ask questions. 
Message Thread:
« Back to thread
