Rear suspension ?

I've searched the topic extensively, but cannot find a satisfactory answer to a question I have regarding my proposed rear suspension setup. I'm using an 8" Ford rear in my Model A coupe, with shackled quarter elliptic springs. I want to use ladder bars, and my question is whether the ladder bars should be run parallel to the springs, (which will parallel the frame rails) or triangulated as with a transverse leaf. Thank you.

Greg.

 

Greg, parallel will not allow the ch***is as much freedom to roll, but will give more effective "push" on hard acceleration. The QE springs won't care much either way. Are you running a panhard bar or relying on the springs to hold the axle side to side?

 

Triangulated or parallel with a panhard bar to control lateral movement is my
recommendation, why are you using the semi-elliptical springs? Something different?

 

The guys are right, a panhard is absolutely necessary. As for parallel vs triangulated, we only have experience with parallel 4 bars and those handle VERY well. The ride is very smooth and on hard launch the car goes straight and hooks.

Don

 

Why is a panhard necessary? Parallel leaf setups locate the rear side-to-side with no panhard just fine.

 

Not if you mount them on a single bolt type perch. Maybe if you lock them in between a two sided gusset. A panhard will keep the rear from wanting to rock sideways on hard turns.

Don

 

4 bar is a better choice.

 

Ok. Thanks for the feedback. I will be using a panhard bar for lateral axle location. For "kwoodyh", I'm using the q.e. setup for a few reasons; lower roll center, ride height adjustability, and decreased body roll. Not to mention increased trunk space. If I just wanted to be different, I'd do something else. This isn't THAT far off the map
I was concerned with running the ladder bars at an angle to the springs, because I thought the spring shackles might bind with suspension travel.

Greg.

 

The shackles will prevent binding with that setup.

Ah, I gotcha Don, I mounted mine with 2 Ubolts each to gusseted plates on the rear of the frame. NO movement there...

 

Yeah, and I don't even know if my formula is correct, but I just tend to overbuild everything.

Don

 

If you have the QE's, do you need the bottem link of the parallel bars? Seems useless in a 4 bar set up. Just asking.............
Yes I think you will need a panhard rod.
The quarter eliptical and the bottem bar of the 4 bar seem redundent.

 

Some people say the spring is sufficient on the bottom, including Posies, who make a QE spring setup. Lots of cars have used them that way too, like Austin Healy Sprite, MG Midget, etc. But to us it seemed that when the spring would compress it would also extend out a bit, changing the pinion angle of the rear axle. And, since we tend to overbuild stuff, as I mentioned above, we simply let the spring do the spring thing and let the four bars control the rear end fore and aft.

Don

 

I agree with Don, in my experience, the pinion angle changes drastically as the spring grows in length. Hard on u joints, makes for vibration too, use a shackle and a four bar, you'll be happier.

 

Watching this one as I plan on doing something similar soon

So parallel or triangulated? Or is it ultimately just down to packaging and preference?

 

I use triangulated, but parralell with a panhard bar is excellent as well. Both work well.

 

Depends on the horsepower and tire. Remember the lower links provide the "push" from the axle to the ch***is. You don't always want a flexible connection in there...

 

So an old style traction bar on the Q E and a stiff bar on the top link would be the "best" way to go???
Not trying to be an ***, but this is an interesting conversation.

 

Do you have pictures of your setup?

 

im taking notes on this!.. ive got QE in box ready to do my build but so many different ways.

 

If you're running actual true ladder bars (like in drag racing) they can only be mounted parallel to the springs. I have never seen them mounted any other way.

A 4 bar is a different story to which I have used both configurations and have had success with both.

 

Do you have pictures? I'm really leaning to a triangulated 4 bar with the QEs as the bottom bars with no shackle.

 

It seems to me that ladder bars running parallel set up the same problem that has been discussed at length regarding so-called " truck arms". That being, control arms mounted rigidly to an axle housing, when parallel or nearly so, force the axle housing to become, in effect, an anti roll bar when there is ch***is/body roll. Since the axle housing cannot twist around it's axis, the bars and/or their brackets will bend or break.

By angling the ladder bars toward the center at the front this problem is alleviated, if not eliminated. Also, a single ladder bar would serve to control axle rotation without inducing "twist" in the housing.

Ray