Wrestling with rear suspension ideas

I have a nice (i hope) boxed perimeter frame on the way and need to figure out what kind of rear suspension to use this time. I'm going for an old school hi-boy look this time with no rear Z. Kinda like the attached pic but not quite that high in the air.

Since the car will be high, the rear susp will be visible, so that's a concern. The other main concern is the terrible roads in the city, so it needs to soak up the bumps well.

On my '29 rat I used coils, 4-link and cushy shocks - worked great. But its not a very pretty setup.

On my speedster (avatar) I used 4-link and coilovers. Rides like a brick, makes me not want to drive it. I have the softest spring rate avail and adjustable shocks. Still way too stiff.

Whatever i go with, it must have the ability to use seperate shocks, so I can use cushy ones. The shocks in coilovers are too stiff.

So I was thinking 4-link with '35 spring behind the rear axle. Looks great but how would something like this ride? Seems like those springs are pretty stiff looking

Other option might be 4-link or ladder bars with coils in front of the axle (to hide them).

I'll go first. In the mid-70's I built a '31 A Town Sedan and used Chevrolet truck arms and Corvair coils. That car is still on the road with the same rear suspension. I would guess the Corvair springs are around 125lbs./inch.

If I were to do something similar today I would consider Pete & Jakes ladder bars. They are long and point toward the trans tailshaft. The triangulation reduces the inherent bind found in parallel ladder bars. And, they are tucked underneath so are not very visible.

Consider coilovers that are double adjustable. You can get springs down to 85lbs./inch which is really light. If you don't want the look or cost of coil overs you could use a soft 12" tall spring that compresses to 9" under static load. That will be soft enough for a good ride. I have used coil over springs and just mounted them in cups. Or, there are 5" diameter springs as light as 125 lb/inch. If you use a regular shock tilt it up to 30 degrees to reduce its effectiveness. Or, get ahold of el Polacko over on the H--B site and have him get some Bilstein shocks that are calibrated for your car. Do this after you determine the spring weight on the rear axle.

I just converted my '27 Chrysler Tub from short leaf springs to home made coil overs. Because the shocks are tilted at 30 degrees I used 150 lb/inch 12 inch springs. If they were vertical I would have used 125lb/inch.

Thanks Bob

The coilovers on my speedster are actually double-adjustable. They are 5" coils, so the lowest rate I could get was 115lbs. I think the key is what you illustrated in that pic - lean the coilover over 30 deg or so to reduce the effectiveness and increase wheel travel. I should have planned for that when I built that frame.

I don't mind the look of coilovers as long as I can make it ride well.

Maybe I'll make at cross member with multiple holes so I can experiment with diffent degrees of lean and spring rates.

P.s. I found that rear shocks for a K-car (Reliant K, Lebaron, Shadow, etc) are very soft and are just right for a light car. $14 apiece too!

If you want it to look old school why not just go with a model a or model t rear spring setup and hairpins ? Up until I did the coil over setup on my current project that is all I have every used and the ride quality is very good IMO. I drive my 27 everywhere and even on long trips it is not uncomfortable at all.

Don

I run a set up similar to the one above, basicly three bar!
But my springs are in front of the axle, just like 70's chevy truck
so I can adjust leverage against the springs! It isn't
triangulated, (if done over I would) but it works well, and
rides pretty good now that I've gotten it soft enough!

It's about as basic of a set up that you could have!!
Only thing showing out back is the shocks!!

I am real pleased so far with my 1/4 eliptic rear. It is very simple and very easy to change sprig rates by adding or subtracting leaves. Basically it is a triangulated 4 bar but the springs act as the lower arns.

All these suspension approached are good. My '27 roadster has a Posies Model A spring and it rides quite well.
I've done quarter elliptic springs front and rear, with and without shackles and they all can be made to work fine.
Thanks for the K car shock tip.
Good luck with the project.
Oh, with your skills you can make your own Pete & Jakes bars is so desired. Save $$$.

BigIrish said:

Thanks Bob

The coilovers on my speedster are actually double-adjustable. They are 5" coils, so the lowest rate I could get was 115lbs. I think the key is what you illustrated in that pic - lean the coilover over 30 deg or so to reduce the effectiveness and increase wheel travel. I should have planned for that when I built that frame.

I don't mind the look of coilovers as long as I can make it ride well.

Maybe I'll make at cross member with multiple holes so I can experiment with diffent degrees of lean and spring rates.

P.s. I found that rear shocks for a K-car (Reliant K, Lebaron, Shadow, etc) are very soft and are just right for a light car. $14 apiece too!

Click to expand...

BI, do you know the extended length of those shocks?
Thanks!!

rainman said:

BI, do you know the extended length of those shocks?
Thanks!!

Click to expand...

21.5" extended, 13" compressed. 8.5" stroke, so lots of room to play with.

My bad, they've gone up to $19.99 now!

I'm going to try some double adjustable coilovers, see how that works. I think I can get it right by varying the lean angle & spring rates