Split crossovers use two shims to form the crossover gap. Split shims smooth the bend radius at the crossover shoulder to prevent kinking of the face shims on the sharp shoulder of a single crossover shim.

Valving Logic dyno testing of kxf450 shim stack on Thumper Talk used a split shim crossover. Shim ReStackor analysis of the configuration shows the crossover closes at a velocity is 64 in/sec, just beyond the dyno test range of 50 in/sec. Damping force is expected to sharply kick up after the crossover closes due to the stiff high speed stack used in the configuration.

The data illustrates a typical dyno test frustration. At the velocity limit of the dyno the crossover gap has not closed. Damping force will increase after the crossover gap closes, but there is no way to estimate the stiffness increase from the data obtained.

The high speed capability of Shim ReStackor helps elevate those uncertainties and evaluate high speed crossover gap closers, and valve port flow restrictions that kick in at speeds beyond the limit of conventional dyno testing.

Dyno test unable to quantify damping force increase after crossover gap closes at high speed