Alright so I decided to figure out the spring rates on my car. I'm not really sure why, it just seemed like fun. You might think that I could just look up these numbers, which I will, but instead lets see how close I can estimate them to be.

Spring rates are expressed in lbs and inches, for example a 600lb spring would take 600 pounds to compress it one inch. The front two springs have the same rates, and the rear two have the same rates.

So, to figure out the spring rate of a specific spring, I would find out how much wieght is resting on it (in lbs), and how far it compresses under that weight (in inches). Simply apply some random math here and there, and then we'll get our spring rates.

So I jacked up the front left wheel of my car, and the wheel dropped from it's original position 4.25inches. With the same thing done to the rear left wheel, it moved 3.5 inches. Now all I have to do is figure out how much weight was resting on each of those springs, and there we'll have it!

My car wieghs about 3000 pounds, so you might just think that 3000/4 = 750 pounds on each wheel. Right? Well actually, the weight distribution front/rear would have a great effect on the results, so we'll have to figure that in as well.

After asking around and searching on google, I found that the wieght distribution for a 1998 prelude base model would be about 62/38 (F/R).

So that means 930 pounds are sitting on each front wheel, and 570 on each rear wheel.

Front spring rate = 930/4.25= 218.82 pounds/inch

Rear spring rate = 570/3.5 = 162.85 pounds/inch

What does this mean? I have no clue.

How you doin?

 

that's more or less right, in both the math and the actual rate, but i believe that the OEM springs are progressive rate, meaning they get stiffer as they get compressed. i don't know what coefficient you'd use to factor this in, either.

you'd also have to factor in unsprung weight, as parts of the suspension and the wheels are not a part of the total load on the springs. then, you also have to consider what angle the springs are at, and use some trig to see how much of mg is in the negative y direction (vs x and z). hmm that's all i can think of for now, but good work :thumbup:

 

Ah yes mr. monkey you are correct, sir. I figured with all the estimations I had thrown in there, that the trig wouldn't change our resluts that much, but I had completly forgotten about the progressive spring rates. Eh, whatever. Sounds good. Good thinking man.

 

Good estimation though, beier, that's the right kind of thinking.

One thing is, that progressive springs BY DEFINITION cannot have a single spring rate. However, what you did show by estimation was that the spring rate **at the point of rest** is approximately what you described. To truly predict how far it will compress before coming to rest, you need an integral function. But that's kinda irrelevant.

=)

 

Sounds good man