This next graph shows a comparison between the stock stack and a stiffer mod stack [1033].

Preload rings were used to increase the compression force at the 1 - 10ips range.

Here's a graph that shows how the mod valve stack increased low speed compression early on.

The blue line shows the damping curve of the stock stack we've been looking at.

The pink line shows the curve of the modified shim stack. The mod stack is quite a bit stiffer.

A big gain in compression force was made at 1 - 10ips. After that, the mod stack is stiffer but the damping curves increase at a similar rate (i.e. the mod stack doesn't continue to increase).

Here is a graph that shows 0 - 20 ips.

For 1 and 2ips, the force looks about the same, then it start to amp up. By 5 and 10ips, it has made a considerable increase.

Next we will compare the mod stack with preload rings from above to a different 2 stage shim configuration [226].

As mentioned, we manipulated the damping curve of the mod stack (pink line) by using preload rings. This preloaded configuration gave us more control over the opening speed, low speed and mid speed of the curve, and allowed us to create a unique damping curve that fit our needs.

The graph below compares this mod stack (pink line) to the conventional stack (green line).

The compression force at 10 and 20ips for the mod and conventional stack are about the same. However, the conventional stacks opening speed is 2.5 times stiffer and the mid speed is 1.2 times stiffer.

Being able to manipulate and control the shim stack gives you more control over where the damping curve starts and ends.

Controlling low speed compression force is the key!

Here is a cropped graph showing the 1 - 20 ips range.

The force required to get the shims to open is much greater for the conventional stack.