Technical Does This Rear Suspension Look O.K.?

My '59 Dodge pickup project was acquired as an unfinished project from the P.O.

One thing he did complete before I took it over was this 4-link rear suspension.
I know: It's not traditional, and it wouldn't have been my choice; but working with what you have is traditional, and this is what I've got.

My question is do I need some kind of locator on it? I don't know anything about 4-link, but isn't there usually a wider angel between the upper and lower bars to keep the rear end centered? I intend for this to be a daily street driven truck eventually.

 

I would put a panard bar on it. Also the shock springs look a little wimpy for a pickup.

 

Grab the frame rails and shake them, if the rear end moves around, you need a panhard bar. I bet what you have is fine.

 

If you put a panhard bar on it, what will happen is that it will fight the triangulated four bar. Don't do it. A panhard bar is needed on a parallel four bar set up.

 

That looks good from here! As long as it's straight and the welds don't look like they were squeezed from a chicken, I'd run it just the way it is. There is plenty of triangulation to keep it centered and s pan hard is only going to make it bind. The coil overs have good angle (they're supposed to intersect the inside edge of the tire at the road surface or at least really close to it), they might need a little more beef at the frame rail for a piece of mind. That's my $.02 worth.

"Just because you can put tap shoes on an elephant doesn't mean it can dance!"

 

I second that motion.

Sent from my SM-N900P using The H.A.M.B. mobile app

 

Your upper links might be a little on the long side according to this.
http://www.how-to-build-hotrods.com/triangulated-4-link.html

 

Agree (sort of) with the Panhard bar.
Why -
Though the upper bars (all four) are nice and beefy, BUT...the angle is pretty shallow. More angle is needed, better to handle the side loads. The length of the upper bars are longer than most, but (see above), their size helps to allow them to take the loads.
There just isn't good "tri-angle" there.

Actually...for as much of a pain in the butt as it may be, I'd remount the upper bars. Move the axle brackets much more toward the center, even into the radius where the center section housing starts. The new front mounts should go as close to the frame as possible, for the steepest possible angle.

IF...you go with a Panhard bar...make it as LONG as possible.

OR...don't drive it hard into or out of the corners...

Mike

 

I agree with putting more angle in the upper arms it will probably be ok the way it is . But while the beds off it's easy to straighten out . The way it is now the side load will cause the bushings to deflect and allow movement . The brackets will be forced to take side load , if the angle is greater more triangulated , the arms are being pulled pushed I.E. trying get longer and shorter . This action puts the bushings under a more natural load . The brackets will be pushed fore and aft instead of side loaded . Or install a tracbar keeping it parallel at ride height will keep it from fighting the small amount of triangulation you have now .


Sent from the frozen North

 

A panhard bar will force the rear end to move laterally when it wasn't designed to move that way. I've a friend with a similar triangulated rear end in his car with a panhard bar that forces unnecessary stress into the rear suspension, loading up the bushings. The longer the arc the less lateral movement.

 

Looks similar to a HQ Holden series which used to work good enough for general driving. On the race versions I think they used a Watts linkage but that is race only.

 

It's quite un-conventional and uses a different set of ideals
It might work - it might not.

It's long like ladder bars, it's kind of "not angled" like parallel 4 bar, & and its kind of triangulated like a triangulated 4 bar. So which set of ideals apply? The guy was an out of box thinker, brilliant or misguided bullshit I don't know- Put it on the road and see because it appears to be an experiment.

A watts link set up will not ever hurt when used in any set up so it's always a great "when in doubt" default idea. A pan hard bar can cause some bind issues. In your set up a pan hard bar IS going to work against the slight triangulation & the same pan hard bar is going to help with the long minimal triangulation. So I'd go with a watts link.

 

I was going to suggest a watts link also. Something else I have seen but not sure of it's merits is a bar with heim joints running from the front of one upper bar to the rear of the other.

 

Thanks to everyone for the input. Now I'm more confused.

The guy who did the suspension comes from the rock crawler world and he was planning on daily driving this, so maybe this design is something those guys like. Welds are all good, and the guy clearly (judging by how he did other things on the truck) has built some vehicles before.

I'll look into a watts link. Seems like more work than a panhard, but a better result maybe in my case. The truck is getting close to test-drive-able, so I may leave the bed off for access and drive it a bit as-is to see what I'm starting with, but it won't be ready for a real road test for some time yet.

As to the springs being wimpy- I plan to put heavy stuff in the bed sometimes, so it may get heavier springs later- it came to me with these springs.

 

i would like to see more angle in the top bars as said by the other guys. And I would beef up the spring/shock mount since you say you may haul some heavy stuff .

 

Your over thinking it, as said by many cut the top bars and brackets off, try to save some of it. Move top bars closer together on top of diff. for more triangulation. You may or may not have to get longer bars. I would also check to see if bottom rear shock mounts could be moved outward a little more to help stabilize side movement. I don't see any need or room for a Watts linkage................................

 

You may have nailed it perfectly when you said he comes from the crawler community. My guess is that the suspension we are looking at has a lot more articulation than we as rodders would like or need especially when we figure to do some high speed driving. Rearranging the uppers would help with higher speed driving though.
On the springs on the shocks I'd do just what it looks to me like you plan. Wait until it's all together then figure out if and what change you need to make.
To me the shock brackets look more than stout as everything is in double shear and the lower bracket looks a lot stouter than most rods run.

 

Leave the bed off, drive the fucker and see what you got. Then if you need to make changes you ain't wallerin' around under it to change things.

 

Adding triangulation to the upper bars is a good idea is it will obviate the need for a panhard bar or Watts link. As it is set up right now a panhard bar would probably work if it was long enough to work in a shallow arc due to the fact that the upper bars don't have much triangulation and thus will allow a little lateral movement of the housing --therefore making some sort of lateral locator a good idea.
Moving the lower shock mount outboard will not stabilize side movement and will simply reduce roll resistance due to the shock rate becoming less linear. The method of locating the axle housing is what stabilizes side movement, the spring/ shock package is what holds it up. The more that the shock is off vertical the more that the spring and shock rate will fall off as the rear end travels. Moving the entire shock (top and bottom) further outboard of the longitudinal roll center will make it more effective while leaning it over does the opposite.

Roo

 

If you move the uppers closer to the diff it looks like you could get a little more clearance for the exhaust. Right now it looks like the uppers would hit if you jacked up on the frame. Good luck.

 

Looks like it'll ride nice and smooth. The springs, while at 1st blush they look a bit light, may not be a bad choice. The farther back behind the axle you go with coil overs the less in/lb rate is required. My coil overs were behind the rear axle by maybe 2 1/2" (or whatever those standard mounts were) and I was supporting a car that weighed over 3500 lbs. with 110 in/lb springs. To be fair it was a drag car and mine were vertical but it worked well and even rode nice on return roads. I don't know why it works like that, leverage I reckon, but springs do more than carry weight. They store energy to create rebound for control too. As was suggested above, shake the hell out of it side to side and see what does what. It might be just fine as is. The sway bar below the axle, that's also apt to provide spring function assistance. Looks like a fairly stout one. Run it...

 

As I tell my wife to keep the harmony ...."Honey, your rear suspension looks fine. No, the tires don't make your rear end look big"....

 

I have a similar setup in my truck. It wasn't too bad as is but my tires are close enough to the inner fenders that they rubbed in hard turns. I added a panhard bar, problem solved. With the side movement I had and short suspension travel (about 3 inches), the small amount of change in the panhard bar doesn't cause any binding.

 

Any side loading (in a cornering situation) that allows the rear to move laterally (when not located by the suspension links) will simply tend to rotate the shocks around their mounting points unless they are extremely laid down and in that case you have just thrown the spring and shock rate out the window. As I stated in my post, the springs and shocks are meant to hold the car up and stabilize the suspension motion, not locate the rear end. When the vehicle is in a cornering situation the outboard shock/spring carries the most load and laying the shock over just lessens the ability for it to do that effectively. The further that the car rotates around the longitudinal axis the closer the upper and lower mounts get (in the horizontal plane) and the less effective the shock and spring become as they move less for the same amount of vertical travel. A small amount of angle (as seen it the OP's photos) is usually good depending on the height of the roll center.
When I raced (owner not driver) my circle track (dirt) Corvette back in the 80's most of the opposition had the rear shocks laid over at fairly high angles to stop "sway". When the track got rutted up late in the evening they would bottom out the suspension in the big holes while my car with the shocks actuated by a rising rate linkage did not. In my case the shocks were actuated by a link off the rear axle that was free to articulate so they provided no lateral force on the rear end at all. Once again, the suspension linkages were what kept the rear centered, the springs simply held it up and the shocks controlled the motion.
I can dig out my old Wm. C. Mitchell suspension analysis software and run the numbers if you like but I can tell you from experience laying the shock down is not the way to go. Another good reference is Carroll Smith's Tune to Win (Chapter Six deals with suspension geometry).

Roo

 

In layman terms, the angled springs, by definition, will RESIST side movement but will not PREVENT all movement. That requires a solid link somewhere in the design (panhard, triangulated, watts, etc)

 

Rooman, I don't believe ever thing I read here or in books. In the time it would take me to read a book or fiddle around on a computer program I could have the OP's rear suspension working as it should for a daily driver. He's not building a Moon Rover. After saying all that if I were to go racing I would want YOU on my suspension team! Happy New Year to all and good luck to the OP!

 

As a crawler suspension that's still sux. Needs more angle on the top bars as the others have said or you can add angle to the bottom bars in opposite direction to get a double triangulated suspension.

What you have there will have quite a bit of deflection side to side, shaking the truck with your hands won't tell you anything as you are putting at best a couple hundred pounds of load on it, running driving it will be getting a lot more than that.

You can add a panhard bar to the existing setup without causing a whole lot of issues as long as its properly designed.
Make it as long as possible and as level as you can. The amount of side to side movement created by the track bar should be minimal and easily absorbed by the bushings.

The truck arm suspensions on the 60's Chevy's had long triangulated arms and relatively short panhard and they work fine.

BTW we love articulation in the rocks,,,,

 

I'd never present myself as the king dick suspension guy but I've done an awful lot of rear suspension installations. What we can't see in the picture is how much angle is in the bottom bars. They don't look straight, looks like a little bit of narrowing up front. In order to answer your own concerns the total of both angles from dead center is the triangulation you have in your favor. I didn't see that in the replies offered. Based on the construction quality we can see and your knowledge of the man's background there's not a lot to worry about back there. Adding a panhard bar or a Watt's link? I don't see enough real estate behind that axle to get a good clean installation of either one. What hasn't been mentioned or offered, and I wouldn't raise a rt hand as to feasible street usage, a wishbone locator might be an option. Drag racers started using em in the mid/late 90s more often. Since there's a sliding componet to some of them I'm not sure how you'd keep it clean on the street, but mounting one on top would seem possible and the last option for available room. This assumes you even need something. Add up both angles to see what you have and dig around to see what an optimum angle would be for positive lateral control. I know it's not a "some's good, more's better" thing. Share that dimension her too. Maybe some of the really accomplished suspension guys can help better with that info.

 

The geometry involved looks remarkably similar to Chevelles to me.