kxf450 split shim crossover
Split crossovers (sample apps) 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 data
Shim factor scaling
MXScandinavia dyno tested shim factor equivalent shim stack configurations on Thumper Talk to determine the accuracy of shim factors in scaling suspension setups. By shim factor theory (linky, physics), a stack of 4x40.3 face shims should be 3.8% softer than a stack of 14x40.2 shims.
Dyno test results shows the actual difference was approximately double that at 7.7% shown by the data points in the figure below. Shim ReStackor analysis (lines in the figure below) show the same 7.7% difference in damping force.
rmz450 trapped crossover
Valving Logic on Thumper Talk tested trapped crossover shim stack configurations. Differences in the number of face shims, crossover configuration and high speed stack stiffness makes it difficult to guess the expected damping force differences between the two shim stack configurations.
Computing the damping force of complex shim stack configurations with multiple differences in the crossover configuration, high speed stack and clamp is the central purpose of Shim ReStackor. The computed results (lines) closely follow the dyno test data (symbols).
