Increasing the shim stack clamp diameter produces a progressive increase in damping force up to the point where the shim stack clamp overlaps the inside diameter of the valve port (r.port).
Further increases in clamp diameter physically closing off a portion of the valve port and produce large changes in damping force due to the reduced port flow area.
Dyno tuners point to the effect as an example of the nonlinear behavior of shim stacks. In reality, the sudden increase in damping force is simply due to closing off the valve ports.
However, the approach can be useful to produce more shim stack control on large diameter valves that produce too much flow.
Shim stack clamp washer
Shock absorbers use thick heavy clamp washers purposely designed to never bend. Some KTM setups use thinner clamp washers and under high load the clamp washer will bend slightly which can produce significant changes in damping force as the example below demonstrates.
For accurate results, Shim ReStackor requires the final two entries in the shim stack listing to specify the shim stack clamp washer and nut dimensions so the calculations can evaluate any potential deflection of the clamp at high force levels.
Failure to specify a ridged clamp washer will often cause the calculations to hang in an endless calculation loop.
