Thread: Panhard bar opinions

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The weather should be warming up soon and I'm contemplating getting back on my '57 Chebbie. I've installed a 4 bar rear and am trying to decide how best to locate the rear end housing. The 4 bar kit came with a track locator bar, but a number of years back I broke one of them in a corner and experienced a "challenging" recovery to get the car stopped without a big wreck. I've determined they are best for drag race cars and not for street cars. A Watts Linkage is of course the best method, but with a narrowed housing, 4 bar brackets, coil over mounts, stabilizer bar and mounts things are getting a bit crowded around the housing. A Panhard bar would be the easy way to go, but I'm curious of what you folks have for opinions on whether or not a Panhard bar cares which end is mounted to the frame and which end is mounted to the housing? Oh yeah, the front is a straight axle with leaf springs if that goes into your considerations. Thanks in advance.

I've typed 2 or 3 different replies... 8-) but I'm re-writing this again as I think you already know the answer(s) , I don't believe the link cares what end is where. If it's straight, curved, zig zag means nothing imo. The distance from connection point to point is all that matters. I do know that you'll need to make it as long as practical so the travel arc minimizes the axle travel side to side.

i've used lower 4 link bar . also helps center the rear . no lateral movement with travel .

Not sure if there is real reason, but all the panhard bars I have ever looked at have been anchored to the frame on the right side. This may have something to do with chassis loading from engine torque, but I can't say for sure.

I have had 2 vehicles with panhards. My T-bucket and my Ram truck. Both have 4-bar rear suspensions. The T-bucket had a very short bar (around 18") and the Ram is much longer (probably 40" or so). On both vehicles I can feel the body floating sideways on the suspension when you go from compressed to extended rapidly. There is a particular road near my house that has some close spaced rolling dips that causes the suspension to move almost through it's full travel if you are going too fast (which I usually am). However, I have never felt it in normal driving, but I do find it annoying.

Keep your bar as long as is practical and level with the ground. Being level keeps the sideways movement the same in both directions of travel. Make the bar heavy duty. I would use at least 1 1/4" tubing with a 1/8" wall. The loading can get high when the bar is in compression. In that situation, only the strength of the material is resisting bending. That 57 will have a lot of load on the bar when cornering, considering the body overhang.

Make the frame brackets strong with diagonal bracing.

Where the bar crosses the centerline of the rear suspension will be the roll center. I would probably try to keep that a little higher than the front roll center, which would be where the leaf springs attach to the axle (centerline of chassis). Keeping the rear roll center higher makes the roll axis run downhill the to front of the car and usually will help give a little understeer, which is way safer than oversteer.

Hope some of this helps.

The Panhard Bar on my '33 Coupe is from Pete & Jakes, and is anchored to a bracket high on the driver's side frame rail and then uses the 9" Ford center section bolts, biased to the passenger side. That makes the bar only about 24-28" long, but I justified that against the limited suspension travel on the rear. If I were doing one from scratch I'd make the Panhard Bar as long as is practical, anchoring on one frame rail to a point very near the opposite frame rail. The longer Panhard Bar minimizes the side travel of the differential as the suspension works. I don't believe it matters which side anchors to the frame for a street car.

Thanks for all the great advice, reminders, and "evidence" from your current apps. The weather is supposed to start warming up next week, I'm just too cheap to turn the heat up and get to work when I'm only working on my own stuff!

Dave, I goofed in my reply. I meant to say that all the panhards I had looked at were anchored to the frame on the left (drivers) side. Sorry for the confusion.

Mike had some really good points about the geometry in his post, and it prompted me to try to find what I remembered to be a very concise explanation on YouTube. I had forgotten about the "pre-load" step to minimize, and almost eliminate side play by calculating (or measuring) the "Sagitta" and setting your differential offset from center by 1/2 of the Sagitta value. Then as the suspension travels the side to side movement is 1/2 of the total, likely barely noticeable! Here's a link to a really good explanation - https://www.youtube.com/watch?reload=9&v=liR1--EHMg8

Thanks for the link Roger, a good refresher on geometry is always helpful. Once I get back working on the car I'm still hoping to find or make room for a Watts linkage, but if not I do have references for a proper Panhard bar install!

Just a quick comment on the Watts link. I found out that they can make routing exhaust more difficult. The Watts layout has one high link and one low link so that the pipes may not be symmetrical. I finally had to run the pipes under the rearend. I don't particularly like that solution, but that's what I had to do. Your 57 probably has a lot more room than my project did, so this may not be an issue for you. Just thought I would mention it.