Stack diameter, thickness, order, clamp area and crossover design all influence damping direction.
How a stack makes damping
Shim stacks are thin spring-steel discs clamped over piston or valve ports. Oil pressure lifts and bends the shims, so the stack becomes a controlled restriction that changes with shaft speed and pressure.
What changes the curve
Larger diameters, thicker shims, more face shims, clamp diameter and crossover gaps all change how easily the stack opens. Small hardware changes can move low-speed support, mid-speed comfort or high-speed blow-off in different directions.
Workshop checklist
- Record shim diameter, thickness, order and clamp size before disassembly.
- Match the stack change to the speed range of the rider complaint.
- Compare calculated stiffness with bleed and piston-port area, not shims alone.
- Keep a baseline stack so every test has a known reference point.
Next step
Use the calculator for stack comparison, the handbook for deeper theory, or the workshop booking form when the bike needs service or valving work.