1970 'supreme

Torn on what to do here and it's holding me up from ordering the rest of my suspension parts...

I'm looking to replace my rear springs. Moog lists two versions for the '70. One looks to be a standard duty and one a heavy duty. They are both listed as constant rate springs so I know the heavy duty isn't a cargo coil.

The previous owner put cargo coils in and frankly I am not happy with the stance. I'd like to put it back to its factory ride height I just don't know which way to go. Does anyone know what spring I should be using? or have specs on the original spring so I could cross reference it?

I plan on doing a mild suspension "upgrade" so would a heavy duty spring be better or is that going to leave my rear end lifted? Just to clarify by upgrade I mean replacing all the worn bushings adding sway bars front and back (bigger on the front) as well as new shocks all around.

Thanks Folks!

 

Below is the Moog spring data I have from a very old Excel file. Pay no attention to the prices for the springs as that is pricing data from a very old Moog online catalog.





Here are the specs for the above springs:



The front spring data shows both springs will be the same installed height but the 5386 is a bit stiffer (334 vs 317 lbs/in).
For the rear, the 5385 will sit 1/2 inch higher and is MUCH stiffer (167.5 vs 119 lbs/in).

 

This is awesome. Thanks for sharing.

What are your thoughts on the stiffer rear spring? Is this a better choice if I'm looking for better handling with original ride height?

 

When I changed springs, I was aiming for the FE2 heavy duty suspension setup. I used Moog 5536 front springs. They had the same ride height as the original 40 year old springs. I really like them as they are much firmer for improved handling (488 lbs/in) but still retain a smooth ride with no harshness.

The rears were bought from PST before I knew much about springs and were simply advertised as "442" springs. They may be the equivalent of the Moog 5409 springs. Below are the specs from the Moog catalog. Note that the 5409 rear springs ratings are in between the 5385 and 6321. It seems to me that 167 lbs/in is kinda stiff for the rear, but I am by no means an expert on this. I would recommend you try to balance the front and rear spring rates, which is why I tried to copy the FE2 suspension.

Moog springs
Front:
> 5536
> 442 small block - AC - heavy duty, 442 big block - no AC - heavy duty
> wire diameter = 0.690"
> load height = 11.000"
> load = 1984 pounds
> rate per inch = 488 pounds
> free height = 15.063"

Rear:
> 5409
>All 442 applications
> wire diameter = 0.554"
> load height = 7.50"
> load = 847 pounds
> rate per inch = 143 pounds
> free height = 13.44"

Here's some info from a discussion about springs a while back:

https://classicoldsmobile.com/forums...de-height.html
This pic shows how my car sits with the above springs:

 

Your not going to see much difference between the 2 rear springs Kenneth has on his chart.
If your comparing spring part numbers this chart comes in very handy:
http://www.moog-suspension-parts.com...il_springs.asp

 

That's the modern version of the Moog online catalog that I copied over a decade ago and pasted into an Excel spreadsheet. I had forgotten I had it on my computer until just this past weekend. As said, it's extremely useful for comparing springs specs. Knowing what the car had from the factory makes it a lot easier to figure out which ones are stiffer or softer and helps with getting the ride and stance you want.

 

That is a great chart. I'll have to save a copy and print one as well for my files for future reference.

As it stands I decided to go with the stock spring. Cargo coils just rake the rear too much for my liking and I want a firm but smooth ride. I don't drive the car all that often and i'm also afraid that stiffening the rear springs might cause over/under steer.

great information though. Maybe when I build my next car I'll do something wild

 

I would have no concern using the higher rate HD springs listed in the catalog for the 1971 442 as that is what Olds put in the cars from the factory (yes I know there were no 350 cid 442s in '71 but the 5536 front spring is listed elsewhere for 350 cars and 455 w/o AC).

My choice would be the 5536 up front and 5385 or 5413 in the rear. That would give you a "factory matched" set of HD / FE2 springs.

 

Fun71, if the Moog catalogue is 'online' it cannot be very OLD.

 

Ha! It's all relative. In internet speak it's ancient.