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Discussion Starter #1
I am getting so tired :sleep:of tearing apart my front end. My TCI clip for my '66 came with 350# springs that were mismarked as 300's. So they sent me 300# springs. I drove with those over 400 miles. The ride was rough, shaking fenders and topping out on dips. The lower control arms measured +4 degrees to the floor of my garage which is flat. I ordered and swapped them out for some Heidt's 275# springs and I couldn't believe the results. The car is now 3" lower than before. The Lower arms now measure -5 degrees to the floor. So I went from too high and stiff to too low and soft but the ride now matches the new rear multi-leafs. I have aluminum heads and the battery is in the trunk.
If I cut a half coil off the 300's the spring rate will go up, it will ride rougher but the height will probably be closer to correct. So my next suspension tear down will be to add some Heidt's 3/4" coil spring spacers that will arrive Tuesday. I hope this works. All I want is a decent ride with proper ride height. Now I wish I'd put in the air bag suspension at the start.
On another note, the Heidt's 275's came in bare steel not powder coated or even painted. I dropped another $80 to get them black powder coated. So I received no satisfaction from a $200 spring change. I questioned several powder coating outfits in the Denver area and they all cure the powder on springs at 400F or below. I was concerned about annealing them. My coater cured them at 385F and said he has never had a problem with all the springs he has done for years.
So I hope the spacers and 275's work out okay. I'll find out next week.
 

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I went through the same thing after i scraped a whole in my oil pan. The old springs were very soft and it bottomed out one day while racing. So i bought some stock springs for a 78 mustang II from my local auto parts. They told me they were rated at 317lbs. After my brother installed them the car sat too high, so he cut a full coil off and re-checked it. It still sat a little high so he cut another 1/2 coil. Heres a couple of pics, first one is with the old springs second is with the new ones:



 

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Discussion Starter #3
The spring search goes on

Nice '65 you have. I had a '65 SS 327 4sp in college. My Avatar picture is a drawing a guy did way back then of it with some added height and tires. It was maroon with black interior. 12.90 at 110 was the best I could do.
I'm still waiting for my urethane 3/4" spacers to arrive to raise it back up and make the lower A arms parallel to the ground. If they continue to sag over time I guess I'll cut the 300's a half coil and live with it until a better brand of spring comes along. TCI is supposed to be offering more some day. I'll keep watching for them. They are a good outfit and are always helpfull. Have fun at the drags. Those are impressive times, keep it up.
 

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This is the first I've read that springs were too soft.
How can removing a coil from a spring make it stiffer? I say the spring rate will decrease. There is less material to move and work against. I've posted this before. The springs are too tall from too many coils in them. By the time they are compressed and installed, they are quite tight and it takes more force to compress them further for proper travel. The vehicle weight alone won't provide enough gravity force to do this. The more a spring is compressed, the force required to compress it further increases geometrically. By removing a coil, you are reducing the requried force needed to compress the spring. The spring coil tube diameter determines much of the springs rate. The thicker the material, the harder the force it takes to move and vice versa. Even Heidts mentions in their crossmember installation instructions in the last paragraph that its recomended to cut coils 1/4 at a time to achieve the correct ride height.
I cut one full coil off my 350 rate springs and it actually helped lower it and gave it travel to move and bounce.
I think I would have cut on those 300 rate springs first before I spent $200+ on new springs and powdercoating. Now you're spending more money on spacers.
I hope that will work out for you.
You would think Heidts would of had this common problem with spring rates for a 1st gen Nova figured out by now. But I tell you what, I bet they sell a whole lot of springs to those trying to get these suspensions dialed in correctly on various types of vehicles.
 

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Rotorbolt...are you using 350 rate spring in your heidts front clip?
Tom
Yep. From what I was told. They are Heidits 350 rate with one coil cut off. Bought em from a member here and he suggested cutting a coil off at least since I am running a 6cyl. Good advice.
 

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Discussion Starter #8 (Edited)
Cutting coils really does increase the spring rate

This is the first I've read that springs were too soft.
How can removing a coil from a spring make it stiffer? I say the spring rate will decrease. There is less material to move and work against. I've posted this before. The springs are too tall from too many coils in them. By the time they are compressed and installed, they are quite tight and it takes more force to compress them further for proper travel. The vehicle weight alone won't provide enough gravity force to do this. The more a spring is compressed, the force required to compress it further increases geometrically. By removing a coil, you are reducing the requried force needed to compress the spring. The spring coil tube diameter determines much of the springs rate. The thicker the material, the harder the force it takes to move and vice versa. Even Heidts mentions in their crossmember installation instructions in the last paragraph that its recomended to cut coils 1/4 at a time to achieve the correct ride height.
I cut one full coil off my 350 rate springs and it actually helped lower it and gave it travel to move and bounce.
I think I would have cut on those 300 rate springs first before I spent $200+ on new springs and powdercoating. Now you're spending more money on spacers.
I hope that will work out for you.
You would think Heidts would of had this common problem with spring rates for a 1st gen Nova figured out by now. But I tell you what, I bet they sell a whole lot of springs to those trying to get these suspensions dialed in correctly on various types of vehicles.
I know that it seems like fewer coils would make a spring softer but physics says the opposite. The formula for coil spring rate is:

k=Gd4/8nD3 (the 4 and 3 are exponents)

k=spring rate lbs/in
G= material rigidity or torsional modulus
d= wire diameter
n= number of active coils
D= mean diameter of spring

So when you remove a full coil you decrease the value for n which will raise the answer for spring rate k. This is why I don't want to cut a coil since I don't really want a rougher ride.
I got my urethane spacers in the mail and I'll see how they do with the soft 275's. If they bottom out or make the ride soggy, I'll cut some off the 300's and find some rough roads to break them in some more. There's lots of those in Colorado. Wish me luck.
 

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I know that it seems like fewer coils would make a spring softer but physics says the opposite. The formula for coil spring rate is:

k=Gd4/8nD3 (the 4 and 3 are exponents)

k=spring rate lbs/in
G= material rigidity or torsional modulus
d= wire diameter
n= number of active coils
D= mean diameter of spring

So when you remove a full coil you decrease the value for n which will raise the answer for spring rate k. Wish me luck.
I checked the formula and plugged in some random values. then changed the value for n to the next lower number and you're right. the rate value k does go up, but not a whole lot. So I guess this proves me wrong. But there are other variables to consider. such as vehicle weight and the values for G and d for the spring. Which probably differ vehicle to vehicle. Does spring temperature even factor in?
So according to this formula, the spring rate will theoretically doubble if a spring is cut in half. Making a 350 rate spring into a 700 rate spring. So it takes more force to compress less than less force to compress more. Interesting and confusing at the same time.
This would make for an interesting science project, if I was still in high school.
Sometimes what works on paper doesn't always work in real world situations.
I just know what worked for me. I had to cut a coil just to at least get the spring to fit and work better than what it was. I think I was looking at this in terms of geometry.
I was going by installed compressed height vs. the number of coils vs.the required force for futher compression vs. the remaining spring distance travel before bottoming out under full coil compression. Does this formula apply to a springs installed compressed height already under tension or in its fully relaxed state?
I wish you the best of luck on getting your suspension dialed in.
 

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My '62 looks like a gasser, but that is not want I am looking for :no:. There is no bounce at all with the springs I got from TCI. I suppose I will try 300# and cut a coil if need be. Changing them a few times does not sound like fun to me. I fugured maybe it was the LS1 but it sounds like it is just a TCI issue.
 

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Discussion Starter #11
I checked the formula and plugged in some random values. then changed the value for n to the next lower number and you're right. the rate value k does go up, but not a whole lot. So I guess this proves me wrong. But there are other variables to consider. such as vehicle weight and the values for G and d for the spring. Which probably differ vehicle to vehicle. Does spring temperature even factor in?
So according to this formula, the spring rate will theoretically doubble if a spring is cut in half. Making a 350 rate spring into a 700 rate spring. So it takes more force to compress less than less force to compress more. Interesting and confusing at the same time.
This would make for an interesting science project, if I was still in high school.
Sometimes what works on paper doesn't always work in real world situations.
I just know what worked for me. I had to cut a coil just to at least get the spring to fit and work better than what it was. I think I was looking at this in terms of geometry.
I was going by installed compressed height vs. the number of coils vs.the required force for futher compression vs. the remaining spring distance travel before bottoming out under full coil compression. Does this formula apply to a springs installed compressed height already under tension or in its fully relaxed state?
I wish you the best of luck on getting your suspension dialed in.
Thanks,
The formula applies no matter what the load is. The value for G (modulus) is a very large number so lowering n one coil will cause a significant change. I find this easier to undrstand by thinking about trying to bend a small rod of steel. If it was 18" long it would be easier to bend than if it was 12" long. There's more rod and you have more leverage to bend it. It works the same way with coil springs. One more coil means a longer piece of material so it take less weight to compress it an inch.
Tomorrow I will put in the 3/4" urethane spacers and check out the ride and lower A arm angle. If it is too soggy a ride or bottoms easily, out they go and the 300's go back in. But if the ride is nice and the A arms are paralell to the floor I'll keep them in. The quest for the perfect stance and ride continues...............
 
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