08162019 09:03 PM 
techinspector1 
Begin by finding the coil diameter.
Measure the outside diameter of the spring. (for instance 5.375") Write it down.
Measure the inside diameter of the spring. (for instance 4.125") Write it down.
Add the two figures together and divide by 2. (for instance 4.750")
That is your coil diameter.
With a micrometer or dial caliper, measure the wire diameter.
(diameter of material that the coils are made of, for instance 1/2 inch (0.500"), 9/16 inch (0.5625"), 5/8 inch (0.625) and so on. If the car is together, just hook the jaws of your dial caliper or vernier caliper or electronic caliper onto a wire and measure.)
Count total number of coils, subtract a coil for each coil that touches, these are dead coils. Ground flat ends are a dead coil. Start count with cutoff end facing you. Directly above would be one and so on. Not all coil springs are evenly coiled. You can have 1/8, 1/4, 3/8, 1/2, 5/8, 3/4 or 7/8 of a coil (Example 10 1/8 coils, which would be entered into the calculator as 10.125).
Here is your online calculator.....
https://therangerstation.com/tech_li...ringrate.shtml
Easy Peasy.
The rest of you yayhoos should bookmark this site. And remember, a number that is a less than the whole number 1, should have a zero to the left of the decimal point so that the person reading it knows that the number is less than 1. For instance 0.750" for 3/4 of an inch.
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08162019 08:02 PM 
cerial 
235 r15 is going to get you lower cost tires. You can run a all season or winter 235 for under $100ea.
The spring rate can be calculated to get close. But it is really a butt test thing, with something that YOU feel is right for your driving style.
Record your current springs. Get the thing moving. Then you can adjust the rate to fit you.

08162019 06:37 PM 
V8Square 
thanks for all the info. Now, how do I figure out the rate of my springs that I have? Also, here is a pic of one of the SSK's as a street rod

08162019 06:02 PM 
techinspector1 
Quote:
Originally Posted by V8Square
So then, maybe something like a 225/75 or 235/75 may do the trick. I would have about 5" clearance from bottom of my oil pan to ground. What do you think about that? Enough? Guess I could always add some taller coil overs also

In my experience, the absolute minimum is 4" for a streetdriven car. I used to keep a 4" by 4" piece of wood, about 16" long, laying over in the corner of the garage. If I had a component that looked like it might be questionable, I'd get under the car to sweep the block of wood under it to see if it cleared and by how much. If the car is close to being done, this works fine, but if the car is just getting started and you have engine, transmission, cooling, exhaust and so forth to go yet, then you might want to give the item in question a little fudge room. You can figure it pretty closely if you know the front and rear spring rates. 350 lbs per inch is common for front springs, so if you have, for instance, 900 lbs of motor, trans, cooling and other items to go yet, then you can divide 900 by 350 and find that those items will lower the front of the car about another 2.57", or about 2 9/16". Divided by two springs, that's about 1 1/4". It's just math, but if you've got 5 1/4 inches of clearance on the pan, you're golden if the car has most of the heavy stuff on it already.
Let's say that you weigh 200 and your passenger weighs 150. That's 350 lbs supported by two 350 lb rate springs and two 200 lb rate springs. Total spring rate is 1100 lbs, so 1100 divided into 350 drops the body 0.318 inches, or a little over 5/16" when you and your passenger get aboard.
Here are some photos for the fellows who are not familiar with this replica car......
https://www.google.com/search?hl=en&...Wj_AV8Q4dUDCAY
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08162019 05:58 PM 
V8Square 
Quote:
Originally Posted by cerial
What is the project car?
Thinking drop spindles and sua(flip) with or without a block may get you down 2".
Might not even need to relocate shock mounts.

No. I want to raise it 2", not lower it. And, by the way, this is a fiberglass replica of a 1929 Mercedes SSK roadster on a 350 Chevy powered 2"x 3" tube frame

08162019 05:56 PM 
V8Square 
Quote:
Originally Posted by techinspector1
You would need a tire that is 4 inches taller on the diameter, standing side by side.....about 28.2 inches. That would make it 2 inches taller on the radius, raising the car by 2 inches. A 285/6015 should do it, they're 28.5" on the diameter.
Right on Richard, I don't know where my head was at in my math, thanks for the correction.

Thanks. But you know what I was thinking, though, I may need a 225/75 (29.1" diameter) or a 235/75 (28.9" diameter. That way, the 225/75 would be 4.90" taller than my 195/60 and the 235/75 would be 4.70" taller than my 195/60 which would actually make the ride height 2.45" and 2.35" respectively. In my case, that would put the ground clearance, from bottom of engine oil pan to ground at about 51/2" to 51/4". What do you think about that?

08162019 05:48 PM 
cerial 
What is the project car?
Thinking drop spindles and sua(flip) with or without a block may get you down 2".
Might not even need to relocate shock mounts.

08162019 05:23 PM 
V8Square 
Quote:
Originally Posted by techinspector1
You would need a tire that is 4 inches taller on the diameter, standing side by side.....about 28.2 inches. That would make it 2 inches taller on the radius, raising the car by 2 inches. A 285/6015 should do it, they're 28.5" on the diameter.
Right on Richard, I don't know where my head was at in my math, thanks for the correction.

So then, maybe something like a 225/75 or 235/75 may do the trick. I would have about 5" clearance from bottom of my oil pan to ground. What do you think about that? Enough? Guess I could always add some taller coil overs also

08162019 01:19 PM 
techinspector1 
Quote:
Originally Posted by V8Square
Gotcha. So, basically, with the taller tire, I would gain only close to an inch in ground clearance. Wonder what size tire I would need to get a 2" increase

You would need a tire that is 4 inches taller on the diameter, standing side by side.....about 28.2 inches. That would make it 2 inches taller on the radius, raising the car by 2 inches. A 285/6015 should do it, they're 28.5" on the diameter.
Right on Richard, I don't know where my head was at in my math, thanks for the correction.

08162019 01:07 PM 
V8Square 
Quote:
Originally Posted by techinspector1
The larger tire will be 1.89" to 1.90" taller standing side by side with each other, depending on the source of the measurements, but it will not raise the car that much, because the measurement from the centerline of the axle to the ground will be the RADIUS of the tire, not the diameter. I say again, you will gain about 0.95", or about 15/16ths of an inch.
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Gotcha. So, basically, with the taller tire, I would gain only close to an inch in ground clearance. Wonder what size tire I would need to get a 2" increase

08162019 01:00 PM 
techinspector1 
Quote:
Originally Posted by V8Square
That would be, 1.89" taller, correct?

The larger tire will be 1.89" to 1.90" taller standing side by side with each other, depending on the source of the measurements, but it will not raise the car that much, because the measurement from the centerline of the axle to the ground will be the RADIUS of the tire, not the diameter. I say again, you will gain about 0.95", or about 15/16ths of an inch.
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08162019 12:58 PM 
V8Square 
Quote:
Originally Posted by techinspector1
According to the internet, a 195/6015 tire has a diameter of 24.2 inches and a 235/6015 tire has a diameter of 26.1 inches. The difference is 1.9 inches on the diameter, but since we are looking for radius, we will divide by 2 and find that the difference between the two tires is 0.95", or roughly 15/16ths of an inch.
68NovaSS made two errors. The first was a subtraction error and the second was failing to use radius instead of diameter.
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So, would that tire size, 235/60 x 15 give me my approximate 2" more ground clearance I need then?

08162019 12:52 PM 
V8Square 
Tire size
That would be, 1.89" taller, correct?

08162019 12:51 PM 
V8Square 
Quote:
Originally Posted by 68NovaSS
According to my tire height calculator your current tires are 24.21" tall, the 235 tires are 26.10". Doing the math you would see approximately 2.89" increase.
https://tiresize.com/calculator/

1.89, correct?

08162019 12:50 PM 
techinspector1 
Quote:
Originally Posted by V8Square
Currently, on my project car, I am running 195/60 x 15 tires. I want to get an additional 2", or close to it as possible, ground clearance. If I put on 235/60 x 15 do you think that would give me the additional clearance I am looking for?

According to the internet, a 195/6015 tire has a diameter of 24.2 inches and a 235/6015 tire has a diameter of 26.1 inches. The difference is 1.9 inches on the diameter, but since we are looking for radius, we will divide by 2 and find that the difference between the two tires is 0.95", or roughly 15/16ths of an inch.
68NovaSS made two errors. The first was a subtraction error and the second was failing to use radius instead of diameter.
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