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Author Topic:   panhardbar angle question ?
dluna
Member
posted May 31, 2003 10:14 AM
I have been trying to reason what exactly angle in the panhard bar does to handling, but thought I would ask on here to see if I am thinking in the right direction.

Scenario:
Say you are have a J-Bar running flat with no rake.
You then move the pinion mount down 1" and the frame mount up 1", and lengthen the bar a bit to keep the same rear tire tracking. The roll center would be in the same location, but you now have angle in the bar. Can someone explain what effect an angle only change like this would do to the car? I have always been told to put angle in the bar (raise frame side) when it gets dry, but if you do this without lowering the pinon mount, you are raising the roll center, which is opposite of what you want on dry??? Thanks in advance.


nvracer
Member
posted May 31, 2003 02:01 PM
What you are saying is true with a long panhard bar. But may or may not be true with a J-bar, and is not true with a short panhard bar.
Let me try and explain. With a long panhard bar the roll center of the car is what is called on the bar. If you raise the bar on either side Pinon or chassis the roll center will move up loosening up the car.
With a short panhard bar. Left side of pinon to the chassis the RC is off the bar. If you raise the bar on the chassis it will lower the RC. If you raise it at the pinion it will raise you RC. Now for the confusing part a j-bar is usually off the bar which makes it work like a short panhard bar. But this isn't always true with every car. The only way to know is if you raise the mount on the chassis and keep the rear-end tracking the same and the car loosens up I would say your RC is on the bar. I hope this helps.


hiredgun
Member
posted May 31, 2003 09:20 PM
nvracer is right. I wonder if this stuff is in the tech articles from Afco? Mark Bush is the one who taught me.


WPP
Member
posted June 01, 2003 12:19 PM
I have always heard if you run a short bar with a lot of angle the roll center will move the to the right with the bar hooked to the chassis


Racer17V
Member
posted June 01, 2003 05:28 PM
NV-
I currently run a J bar. I'm on the lowest hole on the pinion. If I move the chassis mount up while leaving the pinion mount in the same hole, what should this do? Does this raise the RC and loosen the car? Also, if you let the rear end slide over without lengthening the bar when you raise it, would this tighen the car (moving the LR out)? I'm trying to tune my car for a dry-slick track, thanks.


nvracer
Member
posted June 01, 2003 06:12 PM
I knew this would open up more questions and I am not sure I can clear them up but will try.
I also run a j-bar, When I lower my J-bar on the chassis it tightens up the car. When my friend lowers his j-bar it loosens his car. So not all cars react the same on adjustment of a j-bar.
Lower the bar on the axle side will always lower the RC of the car, no matter what kind of panhard, j-bar that is run. Tightening and increasing sidebite.
On a dry slick, which are track is I run the J-bar 1" below the height of the driveline and the chassis side between 4 and 5" above that. I have been move it around more this year. It changes the handling of the car greatly with a small change.
Mark Bush is a good instructor, find one of his classes and go. Alot of good information.


dirtsquirt
Member
posted June 01, 2003 10:23 PM
Now that you said something about the roll center being off the bar, I remember reading that a long time ago in the tech articles. I just went back and read the ANGLE section a few times before this post and didn't re-read that part. BUT..the only thing it talks about is the roll center moving toward the stiffer side. There has to be a formula to calculate the rear roll center. Anybody?


devil wrench
Member
posted June 02, 2003 09:19 PM
Mark was working on a program to calculate rear RCs for months. Basically said you can find a general area, but there was no sense in tryin to pin point it because it is constantly moving. It's not easy to find like a front RC.

Dirtsquirt...on a J or a long straight bar, you're correct. The RC is right near the center of the heims, but it does move around with different springs nad suspension motion. On the straight shorty, it's usually more toward the pinion end of the bar, but as you add angle to the bar, the RC can move off the end of the bar to the area of the pinion or even farther.

[This message has been edited by devil wrench (edited June 02, 2003).]

dirtsquirt
Member
posted June 03, 2003 05:48 AM
dirtsqirt part of the answer to your question is because rear spring stance comes into play when trying to find the rear roll center. if you get a chance go to the afco seminar they have several across the country.


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