Kirk! We're under attack!! Suspension help.

[rbgray1]

Joel,

Does a 4 trailing arm setup benefit from a panhard bar?

Can you send me a pic of your setup? Would be very easy at this point.....just not sure Panhards and 4 trailing links go together.

I do know you want the panhard as long as absolutely possible, to create the largest arc possible.

[cycleguy55]

Originally Posted by rbgray1

Joel,

Does a 4 trailing arm setup benefit from a panhard bar?

Can you send me a pic of your setup? Would be very easy at this point.....just not sure Panhards and 4 trailing links go together.

I do know you want the panhard as long as absolutely possible, to create the largest arc possible.

The biggest problem with a Panhard bar is the axle will move in a slight arc - with the arc being reduced through as long a Panhard bar as possible. While there is certainly some compliance in the bushings of a 4-link rear suspension, this is not ideal.

You may want to look at a Watt's linkage ( https://en.wikipedia.org/wiki/Watt%27s_linkage ) - you get the lateral location benefits of a Panhard bar but the axle remains centred. While there is still some lateral motion, it is significantly less than a Panhard rod would produce.

A very thorough assessment of suspension including 4 link suspension and Watt's linkage. It touches briefly on Panhard rods but discards that design due to the issues of arc travel of the axle. https://eprints.usq.edu.au/3971/1/Parkin_2007.pdf

[moore_rb]

Originally Posted by rbgray1

Does a 4 trailing arm setup benefit from a panhard bar?

That all depends on how the upper control arms are positioned.

If the upper arms are positioned parallel (or near parallel) to the lower arms, then a panhard bar will definitely help with lateral positioning in a solid rear axle car.

But, if the upper control arms are angled in, so that they converge near the center point of the rear axle (forming a triangle), then the control arms themselves serve to keep the axle located laterally, and a panhard bar would be redundant.

[C5GTO]

Given the angling of control arms on the CR1, the main lateral movement comes from control arm bushing displacement. If you have "solid" bushings, no or very little displacement. If you have rubber bushings, then there will be displacement under load. Under load is when you really don't want the displacement.

Is a Watts linkage better than a Panhard bar? Yes, but it's more complicated and thus likely more expensive.

Can a Panhard bar be setup to minimize the amount of arc? Yes, through length and setup. On mine, it's length it about that of the distance between the frame rails. For setup, it goes slightly downward from frame to rear end at normal ride height. So when the suspension compresses, the Panhard bar first goes to level and then to slightly upward. Given the amount of rear suspension travel on a CR1 (not a lot) and this setup, there's very little arc introduced by the Panhard bar. And besides, when you're cornering hard it's usually on a fairly flat surface, in other words not a surface with large undulations.

I didn't have a chance to jack up the car and take pictures over the weekend as I was busy welding new mufflers into the side pipes. Let me know if you really want some pictures and I'll try to find some time to take them.

[C5GTO]

Originally Posted by rbgray1

Joel,

Does a 4 trailing arm setup benefit from a panhard bar?

Can you send me a pic of your setup? Would be very easy at this point.....just not sure Panhards and 4 trailing links go together.

I do know you want the panhard as long as absolutely possible, to create the largest arc possible.

Ok, I got a chance to put the car on jack stands and take some pics of the Panhard bar setup. The Panhard bar on my car is 33.5" center to center from pivot points. I've got a 9" in my car but the same setup should work on an 8.8". There's a tube running from the opposite side frame rail to the frame side mount to keep it from moving/flexing. The Panhard bar has about 3/8" clearance with the back of rear end housing and extends just short of the shock absorber. The side connected to the rear end runs under the frame rail.













I hope this helps

[rbgray1]

C5GTO,

Thanks for the pics. Should give me something to consider before I finish the suspension and frame painting.