Why are Shim Stacks Tapered?

If you’ve ever had the chance to check out the shim stack in a suspension fork or shock, chances are the shims are in a “pyramid” style stack-up. What is the reason for this instead of having a stack where all the shims are the same diameter? The common answer to this question is that the tapered shim stack adds a more progressive feel as they flex. This is not true. Both tapered and straight stacks are linear, meaning they gradually increase in stiffness as they are loaded

Tapered Stack VS. Straight Stack

Tapered shim stacks also prevent permanent distortion of the shims. When the shims on a tapered stack flex, they all bend at multiple points spreading out the stress. Tapered stacks allow more clearance before they come in contact with the base plate. Shims on a straight stack all flex the same amount and bend on the clamping shim. The stress on the shims are concentrated at the bending point and the chance of permanent distortion is increased.