(Weight X gravity) divided by weight distribution = spring rate

F: (1000 x 9.81) x 0.60 = 5886

R: (1000 x 9.81) x 0.40 = 3924

Now we just need to put a decimal point in there and round the number up or down to translate it into a usable figure:

F: 5.89 kgfm

R: 3.92 kgfm

Now because the car will be moving forwards (therefore weight going backwards) for most of the time we need to adjust the rear spring rate to take this into account, usually its only a small amount but by keeping a record of our original number we can easily test all the possibilities.

**3924 x 1.1 = 4316.4**

3924 x 1.2 = 4708.8

3924 x 1.3 = 5101.2

3924 x 1.4 = 5493.6
You need to test these until you find which one suits your car, once you've found the right ratio it will make further modifications regarding ballast much easier. Lets say we have found that the 1.3xR fits our car best and imagine that we are now going to change the weight distribution to 50/50.

F: (1000 x 9.81) x 0.50 = 4905

R: ((1000 x 9.81) x 0.50) x

**1.3** = 6376

F: 4.91 kgfm

R: 6.38 kgfm

It should be mentioned that finding your starting point isn't an exact science, I generally start by trying to find the right number to multiply the front spring rate to get it reasonably close to the stock value and then go from there, as long as I keep the same ratio throughout the testing stage I should be able to avoid upsetting the F/R grip balance no matter how much I move the ballast around.

Click to expand...