If you get stuck for data, it is possible to measure and calculate the rate of a helical spring provided that it is not variable rate, tapered, etc. (it's a while since I've seen Ace front springs). You need 3 measurements:

"N", which is the number of free turns of the spring (i.e. not counting the end turns that don't flex).

"R" (inches), which is the mean radius, measured from the axis of the spring to the centre line of the wire. It's easiest to get this by measuring the outside diameter of the whole spring, subtract the wire diameter, then halve the answer.

"d" (inches), which is the wire diameter (this needs to be measured accurately because the rate varies with d to the 4th power).

The equation is:

(d x d x d x d x 187500) divided by (R x R x R x N)

The answer is in pounds per inch, calculated for steel springs.