Stock spring dimensions

[Josh]

I have two springs that came with my car. I am just trying to identify if they are stock or aftermarket springs. Does anyone have the height of the stock front and rear springs?

Thanks!

[Rich]

Does anyone have the height of the stock front and rear springs?
Measured ours sitting in their box -

Front: 14 in.
Rear: 16.5 in.

[Josh]

Well I measured them to be 14-3/8" . Look like they are stock fronts? Or perhaps lowered rears?

[Bitsyncmaster]

Probably more important to know the "wire" diameter than the no load length.

[Josh]

I understand there is more to a spring than the length; the unloaded height could be the same as stock but the loaded could be less depending on the capacities and rate of the spring. Ill put a caliper on the coil later

[Rich]

Measured our OEMs sitting in their box -

Front: 14 in.
Rear: 16.5 in.

These readings are within 1/4 in tolerance in hopes of ID'ing yours.

Good point from Dave M about the wire diameters, so here you go.

Spring wire diameters for the pairs of OEMs we took off the car.

Front: 0.485 in.
Rear: 0.510 in.

With OEM coating, no corrosion. Used dial calipers.

[Josh]

Thanks for taking the time to measure Rich!

[awildermode]

I got close to the same measurements, using vernier calipers. Also, they have some rust, so measurements will vary from others.

Front -

Length: 14.375
Outside Diameter: 4.475
Inside Diameter: 3.500
Wire Diameter: 0.490
Gap: 1.305
Turns: (about) 8.25

Rear -

Length: 16.375
Outside Diameter: 4.515
Inside Diameter: 3.480
Wire Diameter: 0.514
Gap: 1.185
Turns: (about) 9.9

I do not have a way of measuring the compression weight (or know the correct term for it). Hope that helps.

[Nicholas R]

All DeLorean springs have a spring rate of 150lb/in (+/- ~3lbs)

[Jacko]

If you're trying to identify OEM springs as was mentioned above the rears have a heavier wire size. Also as the pic below shows the rears will have a yellow paint smear and the fronts will have a red smear.

18619

[Mark D]

I may be completely wrong, but I could swear I remember reading in a thread here that there were slightly different front springs used throughout production, hence some cars having higher front ends than others. The paint color smear on the spring was said to be an indicator of the different springs.... If I'm remembering correctly there were red, yellow, and blue and had something to do with accounting for variation in the fiberglass bodies and how they sat in relation to the frame.

If what Nick is saying is correct and the springs rates were the same then the colors would have to mean a difference in some other variable... possibly spring height?

Again, I don't know if any of this is factual or not. I did a quick search of the forum and I couldn't find that old thread.

EDIT: Found the thread here:
http://dmctalk.org/showthread.php?886-Is-there-a-difference-in-stock-spring-heights-from-81-to-83-models&p=9092&viewfull=1#post9092

[Josh]

Sorry I havent had a chance to go out to the garage and measure. Thanks for all the input guys. The springs do have a red smear of paint on the one coil.

[DeloreanJoshQ]

All DeLorean springs have a spring rate of 150lb/in (+/- ~3lbs)

How did you come up with this?

I came up with Fronts at 183.01 lbs and Rears at 191.57 lbs using the below formula:


spring rate =

modulus of spring steel* X wire diameter
--------------------------------------------------------------------
8 X number of active coils X mean coil diameter (OD)

*modulus of spring steel = 11,250,000 pounds/inch2*

[Nicholas R]

How did you come up with this?

I came up with Fronts at 183.01 lbs and Rears at 191.57 lbs using the below formula:


spring rate =

modulus of spring steel* X wire diameter
--------------------------------------------------------------------
8 X number of active coils X mean coil diameter (OD)

*modulus of spring steel = 11,250,000 pounds/inch2*

I found the number by helping Cliff measure a couple dozen springs on his spring rate tester a few years back when he was studying different ride heights. We measured a bunch of stock springs, eibach springs, grady springs, and several unknown. Probably about 25-30 springs in all. I know they all focused around one very round number which I'm about 90% sure was 150lb/in. I'll see him tomorrow so I'll double check the graphs to be sure.

I'm not sure how precise pontiacracing's spring rate calculator is. Those are very ideal calculations. For one, being ground flush on both ends, the "number of active coils" on our springs is really up for debate. Plus, it depends whether coil OD is considered from the wire center or from the wire edge. It should be centerline but it depends how the calculator is set up.

Also spring steel is a very specific type of steel. That doesn't mean all springs are spring steel. There's nothing special about DeLorean springs. They're just cold drawn carbon steel wire. I'm curious why they're using 11,250,000 psi from for the modulus of elasticity. Most carbon steel's have a modulus between 27,000,000 and 32,000,000 depending on carbon content. I suppose they could be using the shearing modulus but that seems odd.

[Rich]

I'm curious why they're using 11,250,000 psi from for the modulus of elasticity. Most carbon steel's have a modulus between 27,000,000 and 32,000,000 depending on carbon content. I suppose they could be using the shearing modulus but that seems odd.

Carbon steel has a shearing modulus of ~11,000,000 - 12,000,000. For coil springs the load is mostly resisted by the wires straining in torsion in cross-section so the shearing modulus (G) is the right input, not Young's modulus (E) as in linear strain calcs.

[Nicholas R]

Carbon steel has a shearing modulus of ~11,000,000 - 12,000,000. For coil springs the load is mostly resisted by the wires straining in torsion in cross-section so the shearing modulus (G) is the right input, not Young's modulus (E) as in linear strain calcs.

You're right. Now that I picture the free body diagram, it's definitely a torsional reaction with the center of the wire as the neutral axis. Shearing modulus does make sense.

[Bitsyncmaster]

Do the springs get tempered?

[Rich]

Do the springs get tempered?

I'm not sure, but probably.

This 3-minute video tells part of the story from Eibach, although you're asking about the OEM springs?

LINK: Eibach Spring Production Video (http://automotive-oem.eibach.com/en/products/product-overview/helical_compression_springs)

Watch it and see if you get your answer.

[Nicholas R]

The Eibach's likely do, but no way on the originals. The originals are truly nothing more than bent wire.

Ok, I double checked and got all the numbers. ~150lb/in is indeed the spring rate for *nearly* all DeLorean springs. Please see the following attachments.

Overall height/length vs force
18685

Spring rate comparison between all the different springs.
18686

Ride height comparison for each type of spring.
18687

Here's a shot of the spring rate tester. Combination of a linear transducer and a load cell.
18688

Here are some of the springs measured. I say some because many of the springs measured are also on people's cars right now; mine included.
18684

Like I said, a LOT of springs were measured to collect this data. Multiple sets for each type of spring were compared.

Hope this information helps.

[1batt4u]

My stock springs have Red paint.

I have P.J. Grady's lowering springs sitting on the side, waiting to be installed. I just measured them, they are 13.5" high. Does that mean when installed the car won't sit low, since the stock springs are around 14"?

[Nicholas R]

My stock springs have Red paint.

I have P.J. Grady's lowering springs sitting on the side, waiting to be installed. I just measured them, they are 13.5" high. Does that mean when installed the car won't sit low, since the stock springs are around 14"?

They should still be a little lower.

When did you get them? Far as I know, Grady's lowering springs have been unavailable for several years.

Also, the the chart with the ride height is a relative measurement. The most important thing is the difference between the heights, rather than the actual heights themselves. If I recall correctly the actual number shown is the distance from the wheel center to the lip of the fender. That measurement is pretty arbitrary without a frame of reference but when comparing the different springs against one another, it gives you an idea of how much some lower compared to others.

[jmettee]

My stock springs have Red paint.

I have P.J. Grady's lowering springs sitting on the side, waiting to be installed. I just measured them, they are 13.5" high. Does that mean when installed the car won't sit low, since the stock springs are around 14"?

I thought the same exact thing. The coil geometry is different. I saw about a 1.25" drop from stock. VERY happy with Grady's springs on front....steering & handling changes are significantly better.

[Mark D]

Awesome job on the spring rate and height comparison testing!

http://dmctalk.org/attachment.php?attachmentid=18698&d=1367510503

[1batt4u]

I called Rob last June, 2012, asked if he had a set, he said yes. So I passed by his place to pick them up.

[Mattr04]

Does anybody know if Cliff's ride height graph is still accurate\relevant? Looking at the graph, it show's Martin's springs as having the second-highest ride height for front springs (second only to stock).

I obtained a set of Martin UK springs secondhand, but they look about 3 inches shorter than my stock springs:

33049

I realize they are supposed to be stiffer than stock, and uncompressed height is not a good indicator, but even if they didn't compress at all they are already 3 inches shorter. I've believe I've been told Grady front lowering springs are an inch or less shorter uncompressed, and lower the car something like 1.5-2 inches, so how could it be Martin's springs ride higher (relatively)? Is it a different production run of springs from the vendors that is being compared? It was 5 years ago.

I guess I was under the impression that Grady springs lowered the car the least amount of the lowering springs out there. The graph shows that only Eibach's are lower.

I guess I'm just worried about the springs I was given being "too low", and I really don't want to put the car all the way back together to confirm\deny.

I know also I read somewhere that the paint codes on the original springs meant something. Mine are red (as pictured). Are those a higher ride spring?

Thanks again for the help.

Matt
#1466