Tech Question - Coil Spring Rate and Load

Mike,

I just pulled a set of front coil springs out of my 1967 A-Body, BBC.

They measure 17 7/8" long from end to end and have 11 coils made from 5/8" material

- is there any way to tell the Rate, Load, and Load Rate of these springs?

They have a stamping on them that says 44CH.

Thanks in advance.

-M

M,

To get the Rate we need the wire diameter, the inside diameter, the number
of active coils (not the total coils).

To get the Load we take the Rate and multiply it by the deflection.

There is no such term as Load Rate, it is the same as Load.

Load is the amount of weight the spring will support at a given height.

Rate is the amount of weight required to deflect a spring one Inch.

If a spring has a 200 Lb Rate and it is deflected 3 Inches, then it has a Load of 600 Lbs.

-Mike

Thanks Mike -

All 11 of the coils are active - none of them touch each other.

Wire diameter is 5/8" (.625) and OD is 5".

-M

M,

Going by the specs you give the spring would have a Rate of 233 Lbs.

However, the specs are not right because even though the coils do not touch each other, the end coils, or part of them, are touching something. The part that is touching is inactive and therefore the active length is shorter.

Lets say 1/2 of each coil is touching the mounting plates.

The Rate would then be 256 Lbs. If one full coil is touching on each end then the Rate would be 285 Lbs.

But seeing this is on an A-Body the inside diameter is 3.625 not 3.75 (5" OD minus .625 twice) so the Rates would be 254, 280 or 310 Lbs.

Now, most A-Body BB springs have a Rate close to 310-320 Lbs, so at least one full coil on each end is in contact with the mounting plates.

And you thought this was simple.

Next question.

-Mike