how can i determine the rating of my coil springs? i did replace them from the stock ones years ago but forgot what they are. does it have anythign to do with the diameter of the wire they are made from?
thanks.

 

That's part of it, but the type of material used matters also.

One way to measure is to set the spring on the ground and put a known, fixed weight on top of it, and measure how far it compresses. That'll tell you the approx rate, assuming the spring is linear.

 

easy, Hooke's law. It is the math behind what 67mustang302 is describing. The formula is F=K*x F is the force (weight), K is the spring constant, and x is the displacement. This formula assumes that spring force is linear. In reality that is not the case, but this formula provides a very close approximation and we used it throughout engineering school. The only thing you need to figure out is your units. I believe that most automotive springs are measured in lb/in meaning that a spring with a rating of 610 would create 610lbs of force for every inch that it is compressed OR extended (the force would just be in the opposite direction).

You could figure it out based on the coil wire size,material, # of coils etc., but then you are talking about internal stresses within the spring. Those calculations are a bit more complex.

 

Look at your invoice? Just kidding...

 

You can only get an approximate number with the spring on the car.

You need to:

1. remove a front shock

2. calculate the leverage ratio.

3. Add weight until the spring [not the car] compresses 1".

 

thanks for the info everyone. i will check it out.

 

i may have it. just a matter of finding it after all these years.

 

It's in the folder next to your marbles...
Common ones are 620, IIRC.

 

i found the invoice! they are 600 lb.
thanks.