I apologize if this has been asked and answered a hundred times, but querying this forum is a little difficult. I have finally worked up the nerve to replace the brake lines, front drums, springs and shocks, but I have come across a puzzler. The springs that came on my 65 Corsa don't have a sticker that indicates what they are, but at .510" they're thicker than the .459" convertible springs I purchased a few months back for lowering and stiffening my suspension. My thinking is that a thicker wire should be stiffer, right?. Therefore, either my current coils are aftermarket or HD springs, or the convertible springs are aftermarket replacements that aren't as stiff as what they replaced? Does anyone know the answer to this? It would be a shocker to find out that my car had HD springs. Though born a turbo Corsa, there doesn't seem to be any other upgrades from new--AM radio, non-posi rear end, regular ratio steering arms, box and no extra bright work.

Daniel Atkinson
Tacoma, WA
65 Turbocharged Corsa

The coil count also adds to the stiffness. Fewer coils actually make the spring stiffer.

Find a shop with a spring tester.. Compare Pressure vs height Then you'll know for sure.

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
...............110-PG.................................................Webered-Turbo

This might be a little more information than you were looking for but the math does show the relationship between spring rate, wire diameter, and coil count. If both springs are on the bench where simple measurements are accessable, one should be able to compare the spring rates

[www.thespringstore.com]

James
65 Corsa
SF Bay Area

You leave a lot of information out.

Have you measured the current ride height?

What is the source of your "convertible" springs?

New? Or used?

The diameter of the spring to the thousands of an inch indicate original GM - barring if they are used and you are measuring rust / scale.

Do you know that they are HD springs?

Just a guess, but it appears that the current front springs are replacement. Though, spring ID tags do not last forever.

BTW, without bothering to look it up, HD springs will lower the ride height approx 3/4".

I bought HD springs for the rear of a Corsa convertible. The springs I got had a different wire thickness, different number of turns and different free length than the originals. I measured the ride height at the wheel well before and after and it was exactly the same. This was a little disappointing because I had hoped to cure rear coil sag.
I got into spring research when doing the racecar and it's a deep well. My neighbor is a dirt track racer and has a fixture for measuring spring rate. You can get into differences on how the ends are finished as well.
Bottom line is that your springs may have different characteristics but give a similar result, at least as far as ride height is concerned.

Jim Brandberg
Isanti, MN
CorvairRepair.com

Jim B is correct but given ONLY the dimension you have given the .510 is non stock. You left out the free length of which the coupe HD should be about 12.28" long with a wire dia of .465". The standard spring is is 12.57" long with a wire dia of .447".

Given that above the std spring is longer but softer, the HD spring is shorter but stiffer. The ride height will be the same! You will feel the road more with the HD springs and you will not get as much deflection with the same load applied.

The .510 wire dia reminds me of a Pinto spring, some of the racers use them. I have them also but going back to the cut HD springs.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

JimBrandberg Wrote:
-------------------------------------------------------
> I bought HD springs for the rear of a Corsa convertible. The springs I got had a different wire thickness, different number of turns and different free length than the originals. I measured the ride height at the wheel well before and after and it was exactly the same. This was a little disappointing because I had hoped to cure rear coil sag.
>

Jim - Everything I've read said the Corvair HD springs BOTH made for a stiffer ride AND lowered the car compared to the standard springs.

My four door has A/C and that really heavy fold down rear seat. The vehicles rear end was really low! I kept the old stock front springs and replaced the rears with new standard rate rear convertible rear springs. That raised the back end so it's now level with the front.

Thanks for the advice and information. I need to get myself a pickle fork so I can remove and compare the spring sets. I’ll let you know what I find out.

Daniel Atkinson
Tacoma, WA
65 Turbocharged Corsa

vairmech Wrote:
-------------------------------------------------------
>
> Given that above the std spring is longer but softer, the HD spring is shorter but stiffer. The ride height will be the same!

That is not what is stated in the 1965 Assembly Manual.

HD springs "sit" a little lower.

The cars with HD suspension came with a large tag attached to the steering wheel to warn you that the car sat lower. I don't know if the earlies had the tags but it is shown in the assy. manual for the lates.

RJ tools
Salem,Oregon

RobertC Wrote:
-------------------------------------------------------
> vairmech Wrote:
> -------------------------------------------------------
> >
> > Given that above the std spring is longer but softer, the HD spring is shorter but stiffer. The ride height will be the same!
>
> That is not what is stated in the 1965 Assembly Manual.
>
> HD springs "sit" a little lower.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

I haven't looked at the assembly manual but physics are physics. With the specs I gave which are right out of the GM archives the different springs will sit at the same height. The change on the load rate is only 80 lbs.
Keep in mind I do this very thing on my FC springs my springs are longer than the stock springs but the wire dia. is smaller and that drops the front 2". How can you lower a vehicle with longer springs? LOL

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

For my SpeedSkater using '64 rear coils It would squat! After cutting 5 coils is medium "stiff" and set at the desired height and had 4" of travel for a 1400 lb car.

Pic with powerpack out!