Panhard Setup vs. Roll Center Change

Ok, This question is for the racers. I've lowered my truck, which has the long trailing arms with coils (airbags) and a panhard rod. I'm moving the pan hard mounts for minimum arc & rearend off-set.
Now the question is, would moving my panhard mount on the Frame be better than moving the mount on the axle?, and how would my roll center be effected if at all?
Any body deal with this before? any equations to use? or am I just overthinking all this?

BYC

 

Ideally the panhard bar is level at ride height.Other than that,I wouldn't sweat it too much.If I had to move one of the mounts,and it involved welding,I'd probably try to move the one on the frame so I didn't have to worry about distorting the rear end housing.

 

I think the roll center on an axle with a panhard is understood to be at the height where the panhard crosses the centerline of the car, so moving mounts would indeed move the roll center.

 

The hight at the centre of the Panhard bar is the hight of your rollcentre.
Ideally the Panhard bar is level, and that is why it needs to be as long as possible, to get the least amount of angle for a given amount of suspension travel.
I Homebuid a Road Race car once with an adjustable Roll Centre on the rear ( De Dion) Axle, and I found that to be an more powerfull tool to change Under- and Oversteer Than the swaybars.
That is why I dont understand that most 1-800 Rods have the Panhard Way high on top of the Rear Axle. ( Must be a Drag Race thing )

 

Hey Mr Shapes!
You KNOW some pictures would be nice!

How high should the roll center be AND how do you set the roll center on a car that has no Panhard bar controlling the side to side motion of the axle/body?

Is there a website somewhere that deals with DIY suspension tuning?

Bill

 

Yeah, Hacker I know pictures are nice. I really enjoy them when some one takes the time to post them.
Trouble is, my Computer knowledge is very limited. In fact I had some real hatred for these things, until the HAMB and the people on it sucked me in. I dont think anything but the HAMB would have been able to do that, and the friends that have known me for a long time still cant beleve it.

There is no hard rule of how high the rollcentre has to be.
It is different from car to car.
It (and the swaybar) determents how much weight transfer you get on that axle. In relation to the centre of gravety.
So it is one of the bandaids you can use to compensate for disign flaws in a car, that upset the handling. (like weight distribution, mismatched tire sizes front to rear, etc.
That is what I had to do on my little Homebuild Racecar (It had some real problems). But in the end it was pretty effective, and it won me a chamionship. (In a small country, but still.....)
So there is going to be a relation between the Rollcentre front to rear depending on all the factors that I named earlyer, and also depending wether the driver likes his car to understeer or oversteer (what the NASCAR guys call Tight or loose)
Besides that the builder can also choose if both these Rollcentres (as a set) are going to be higher or lower.

 

Shapes, Thats some great Info, it was exactly what I was looking for. I actually ended up making a bracked on the frame side with two different mounting positions so I can make adjustments... Still learning here but It's fun, I'll try to post some of my pictures later tonight of what I'm doing.

BYC