Front coils are a common post here but one that I haven't seen is determining what aftermarket type you have.

My case, I have a new set of front coils that I bought about 6 years ago from Corvette Central. They were only referenced as "stock" C3 SB with a/c springs- no rating otherwise. The coils are evenly spaced unlike the originals and I haven't checked the coil wire diameter or coils per inch. I doubt CC made their own springs so how do I tell what these are?

Thanks
Gary

 

Unless you have the company name that makes them and their part number or have access to a coil spring load tester its going to be tough to tell what they are. I am a designer for one of the largest coil spring manufacturers in the world and as far as I know there is no way to tell for sure unless you have the above info and even then after time coils sag and lose their original specs. You can have two different coils that are extremely close to each other but have very different characteristics. If your original coils were not spaced evenly then you had a variable rate coil spring as opposed to what you have now which are contstant rate springs, this is very common when vehicles are no longer in production which I explain at the bottom of the post.

What is it your trying to find out? Load and rate info? Shoot me an email with the following info and I'll see if I can find anything out. Ive got a coil spring part number book here that I MIGHT be able to find a close spring to that one and give you an idea what it is but the material used in making the coil also plays a big part in the specs, so even though I may find a coil that matches your info it may be off from what you actually have. I need the following:

Bar diameter, number of turns, coil height, top and cottom coil ID's

FYI when coils are made new for the OEMs, many times there are quite a few part numbers for each vehicle but once a vehicle is no longer in production only a few coils are made for service. So you get many cases where springs dont match what the originals were. When I replaced the coils in my Chevelle I ended up using small block springs even though I had a 396 in it . . . with the big block coils the car sat way to high. I ended up putting my coils on our load tester here to find out exactly what it was I had before I settled on my new ones.

Chris

 

I know Dee Engineering supplies most of the corvette warehouses with coil springs. They are much shorter than stock sprins and their SB spring rate is 460 lbs. I believe the ID from one side to the other is 3 3/4". I'm not 100% sure but I think it's close.

 

Thanks guys, I have a set of the sb a/c and non a/c coils .I'll have to compare the two.
I wanted to know what the ratings were on them as they that wasn't mentioned when I bought them.
I'll let you know what I find out. Imay be installing a set very soon.

Gary

 

About the only way to find out what they are is to have them checked. The problem is finding someone setup to do it. The only thing I can think of is to call performace race shops and see if they do it or where they send springs to get checked.

 

Gary
I did some minor research on these.

If your springs free length is 12.812 the spring rate is approx 507 lbs. (standard spring)
If your springs free length is 12.31 the spring rate is approx 460 lbs (Grand Touring Spring)

Hope this helps you some.
Dan

 

You got those right, Dan ?
Shouldn't the higher rate be shorter ?

 

Dan, thank you for checking for me, I do appreciate it.

I have a set of springs in the shop that are for a SB- non air, but I didn't get a chance to take a look at them. At home, in my parts room, I have another set- SB with a/c. These are the ones I bought from CC 6 years ago and are Moog #5762 and measure 12.750 +/- .125"

I'm interested in seeing the number of other set for non air cars. I'm pretty sure they are also Moog's as they were purchased at the same time. I have a Moog catalog in the shop so I'll have to look in there too.

Why the difference in a/c vs non a/c, added weight for the compressor???

Thanks,

Gary

 

I'll double check the book again but I'm pretty sure I copied correctly.

 

There a lot more to it than just the height ot the spring. I always think of a spring as a coiled up torsion bar. A torsion bar is esentially a straight round rod made of spring steel. It works by twisting of the rod, one end is held in place while the load is applied to the other end. A coil spring twist as the load is applied. The thickness of the rod, the type of metal, and the length will determine it characteristics. The same is true for coil springs. Height of the spring has little to do, except for fit in the particuliar application.

 

Here is a picture of the new Moog's next to OEM 69 non a/c springs. There no flats on the ends of either, Is that still recommened for the top coil end?

Gary

 

From the way I see it, the springs are 'bent' at both ends. This was done at the factory so the spring is close to being flat at the ends. All the individual coils (on the black spring) are space by 1 1/2" to 2" except at the ends where the coils almost touch the adjecent coil.
I just finished installing my driver side spring last night. My front was sitting at about 28.5" with the original springs so I decided to reuse them since they were not sagging. I now know what people mean by the pocket. The pocket is the area where the end of the spring is designed to be placed. My spring looks more like the black one except I believe I had 7 coils.

 

For what it's worth, I just got 550# springs for my '76 and when I got them they were labelled as BB springs.